Best practice for installing a baghouse magnehelic differential pressure gauge

This simple baghouse accessory can mean the difference between a properly functioning baghouse and an operational disaster! Use this guide to ensure proper installation and maintenance of your differential pressure device.

By Dominick DalSanto
Baghouse Technology Expert and Sales Director

One of the most common issues we identify during our dust collection system audits/inspections  is poorly installed and maintained differential pressure system components (e.g. magnehelic/photohelic gauges, DP air lines, DP taps, etc.). As we have covered in previous articles in this series, having accurate differential pressure readings is essential to proper dust collector operation.

Baghouse differential pressure air lines

Avoid the example here. Avoid splitters and crooked lines.

I was recently asked by one of our readers if we could write an article on how to install the differential pressure reading system components for a baghouse. The process, like many baghouse-related items, is not complicated. However, there are some industry best practices that make maintenance easier and reduce likelihood of problems in the future.

This guide can be used regardless of what kind of differential pressure reading system you are going to use. The process is the same for magnehelic and photohelic gauges, as well as timer boards and control boards with on-board pressure sensors.

Installing a Baghouse Differential Pressure System

  1. Determine what kind of differential pressure controls you will use
    • Magnehelic gauges are simple and provide reliable data. However, they alone cannot be used to control the cleaning system on a baghouse.
    • Timer boards are useful for processes that are consistent in dust loading and operating schedules, but must be manually set by operators.
    • Clean on demand systems are the best choice for controlling a dust collector. Often, these systems are all in one controllers, or they are a mix of a control board with an external photohelic or magnehelic gauge for pressure readings
    • Air lines running between the controls and the baghouse can be plastic, carbon fiber, or even metal (copper or aluminum). Plastic or carbon fiber lines are easier to run, but metallic lines are much more durable and will require far less maintenance in the long run.
    • Consider installing secondary magnehelic gauges for redundancy and easy reading by maintenance personnel.
  2. Decide on the location of your control(s)
    • Locate your controls where they can be easily accessed by maintenance personnel. With smaller units often the most convenient location for controls and gauges will be on the ground level. Good locations include on supports or nearby walls. On larger units, controls are best located near the doors or along access platforms. Common locations include next to the door, above the pulse valves and compressed air header, or on a nearby wall or column.
  3. Decide on the location of your air taps and plan your air line runs
    • Air taps are best placed near the corners of the clean and dirty plenums. This minimizes the amount of dust that can enter back into the air lines and possibly foul the DP sensors. Try to keep them about at least 6″ from the walls and in the corners where practical. Keep both taps near each other for easy access when performing maintenance.
    • Decide on the best path for your air lines. Avoid runs over 100′ as this may affect the accuracy of the readings.

Common Issues with Dust Collector Differential Pressure Gauges

Problem: I hooked up the DP lines, but my DP sensor is giving me a negative reading.

Solution: You likely have the lines mixed up. Try switching the lines on the inputs.

Problem: I have the lines set up correctly, but I am getting very low readings (usually under 1″).

Solution: Before installing the both lines, you need to zero out the gauge. Attach one side and then with the other one off zero out the DP sensor. Now when you attach the second line it should give an accurate reading

Problem: My controller is setup, but the solenoids are not firing.

Solution: Check your wiring to make sure you have everything correct. Often, the common line from the solenoid to the control is mixed up with one of the control wires. Double check everything and follow the wiring diagrams from your manufacture exactly. 

Special Thanks

A special thanks goes out to one of our readers, Tim Skiba, for suggesting this subject for an article.  If you have any topics that you would like to see discussed on, please share them with us in your comments below. Thank you so much for reading.


| Dominick DalSanto is an author & dust collection technologies expert, specializing in dust collection systems. With nearly a decade of hands-on working experience in the industry, Dominick’s knowledge of the industry goes beyond a mere classroom education. He is currently serving as sales director at His articles have been published not only on , but also on other industry related blogs and sites. In his spare time, Dominick writes about travel and life abroad for various travel sites and blogs. now offers free site visits to new customers in the Las Vegas area to all new customers. 

By Dominick DalSanto
Baghouse Technology Expert and Sales Director News | As of May 1st, now offers free on-site visits to all new customers in the Las Vegas, Nevada area. These visits will provide potential customers with a more personalized relationship with the company. Upon request, a baghouse engineer will arrange to visit a facility on-site to introduce the company’s products and services. Where possible, the baghouse expert will tour the facility and examine its dust collection systems. When finished, the representative will review their findings with plant personnel and issue a brief written summery within one week. This will include an overview of the facility’s dust collection systems and general recommendations for areas where improvement can be made.

Benefits of a Dust Collector Report

Free dust collector inspection and report from

Free dust collector inspection and report from

Many of our current customers have benefited from our recommendations. By putting into practice our recommendations they increased efficiency, capacity without large capital investments, reduced down-time, operating costs, and lowered emissions and improved safety (due to air quality) within their facilities.

Here are just some of the items we often identify during a free site visit:

  • Troubleshoot existing issues and work with staff on how to resolve them
  • Filter selection: recommend alternative fabrics, finishes (e.g. PTFE membrane), filter types (e.g. pleated filters
  • Baghouse condition and unit selection:
    • Recommend repairs (structural, pulse valves, gaskets, etc.)
    • Identify shaker and reverse air units with potential for retrofitting into newer pulse jet style
    • Condense several inefficient small units into one larger system,  etc.
  • Examine current operating methods and make recommendations on how to improve efficiency, reduce operating costs and system downtime (e.g. startup and shut down procedures, fan operating parameters, cleaning system settings, etc.)
  • Examine current maintenance procedures and make recommendations for improvement. Includes daily, weekly, monthly, yearly procedures, inspection checklist, handling of replacement bags, diagnosing need for bag replacement, proper bag replacement techniques, etc.
  • Replacing out of date equipment and methods with latest technology, such as pleated filters, clean-on-demand cleaning, PTFE membrane filters, etc.
  • Recommendations for new OSHA standards for combustible dust, such as explosion protection and fire suppression systems.

Request Your Free Dust Collector Report Today!

To request a free visit in the Las Vegas area, simply contact by phone at 800 351 6200 or send us an email and ask for information about our free Las Vegas dust collector inspections and reports.

For more information please see the following pages:


| Dominick DalSanto is an author & dust collection technologies expert, specializing in dust collection systems. With nearly a decade of hands-on working experience in the industry, Dominick’s knowledge of the industry goes beyond a mere classroom education. He is currently serving as sales director at His articles have been published not only on , but also on other industry related blogs and sites. In his spare time, Dominick writes about travel and life abroad for various travel sites and blogs.

Saverstal Steel Dearborn industrial dust collection system

Massive steel mill looks to revise its air permit to allow for proportionally huge increases in its emissions, particularly PM10, VOCs, lead and manganese from its industrial dust collection system. Neighbors say its already emits far too much while the company says it is only a correct to reflect the actual state of the plant and will not result in increased emissions. 


By Dominick DalSanto
Baghouse Technology Expert and Sales Director

Controversy has surrounded a recent application to modify the air permits for a Severstal Steel Mill. Last week, the plant submitted an application to revise its current air permits with the Michigan Department of Environmental Quality for its operations at the Dearbourn, Michigan facility. Specifically, the revisions will allow for large increase in particulate emissions for the plants industrial dust collection systems, i.e. its baghouses. The company says that the revision is not an application for an increase, but rather a modification of the old permit which was inaccurate. The company claims that no increase in emissions will occur, only that the air permit will now accurate detail the existing emissions at the plant.

Neighbors and environmentalists in the area are not buying it. “Just to make a profit, you are going to expose these kids to pollution,” said Haidar Abdallah “That’s wrong.” Given that the area surrounding the massive plant, which produces over 5 million metric tones of rolled sheet and another 1.5 galvanized and galvannealed sheet in 2012, is already one of the most heavily polluted in the country. The EPA estimated the area’s toxicity score as 45 times that of the statewide average.


Looking for baghouse filters? Contact us today for a free quote! Now providing free on-site visits in Las Vegas, Houston and San Diego Areas!

Dust Emissions Increase or Revision to Accurate Levels?

The majority of the debate revolves around differing views on the increases in the plant’s application for the revised limits. According to the plant, “the permit Severstal is seeking from the MDEQ does not authorize us to emit more pollutants. The permit is a technical correction that is based upon the results of stringent testing rather than upon estimates. With this permit correction, Severstal will continue to meet all applicable state and Federal air regulations for the protection of the public health.”

Severstal bought the plant in 2004, when the Rouge Steel (the previous owner) declared bankruptcy. Since then, the company claims to have poured over $1.7 billion into the plant, largely in the form on new pollution controls such as improved dust collection systems. The plant recently upgrading several of its lines with “two state-of-the-art air pollution control baghouses” to control PM, lead and manganese emissions. According to the company, when they acquired the nearly 100 year old plant, it had not and could not provide accurate measurements of its emissions to the state regulatory board. They claim they followed a plan approved by state regulators to “plan, do, check, and act”. They invested in the new control technology, then they proceeded to check the emissions, and now they are simply submitting a now accurate report on the plant’s emissions levels.

While the company’s story does have merit, it is still hard to swallow the large increases bourn out by the numbers released from the application. In some cases, the plant is asking for a revision of over 5,500% of its lead emissions. On average, the company is asking for an increase for emissions of about 725 times the amounts previously allowed for. It should be noted that many of these increases are proportional, the real amounts here are still very small on many categories. (see chart below)

Residents and workers have cause for concern. The dangers from particulate (i.e. dust) pollution are well established and very real. Particulate matter exposure is linked to respiratory health problems and is proven to be an aggravating cause of several cancers and other respiratory aliments. Even more so  the other contaminates involved here, namely lead and manganese pose a health risk. According to the American Lung Association, lead dust exposure  ” can harm every system in the body, particularly targeting the nervous system.” It also can cause severe brain and kidney damage, especially in young children. Additionally, manganese is known to cause severe damage to the central nervous system.

In any case, the company will still have to win over the state regulatory boards to its side to gain approval for its plan. A public hearing on the issue has been scheduled for March 19th at Henry Ford Community College. Information portion starts at 6 p.m. and the public hearing begins at 7 p.m. The company has already invested a large amount of capital into bringing the plant into compliance with state and federal air pollution regulations for particulate matter, lead and other pollutants. Whether or not it has been enough may depend on how severe the public backlash over the dirty nature of its plant and more importantly its response.

Pollutant Location within Severstal plant Currently allowed Proposed revised % increase
PM10 (fine-particle dust) B Blast Furnace Casthouse Baghouse 2.85 lbs/hr. 7.6 lbs/hr 167%
PM10 C Blast Furnace Casthouse Baghouse 5.70 lbs/hr. 18.24 lbs/hr 220%
PM10 Relading fugitives 3.22 tpy (12-month rolling average) 3.6 tpy (12-month rolling average) 12%
PM10 Desulfurization – baghouse 1.55 lbs/hr. 3.6 lbs/hr. 132%
PM10 Desulfurization – roof 6.88 tpy (12-month rolling average) 24.38 tpy (12-month rolling average) 254%
PM10 BOF electrostatic precipitator 37.7 lbs/hr. 47.5 lbs/hr. 26%
PM10 BOF fugitives 7.25 tpy (12-month rolling average) 28.3 tpy (12-month rolling average) 290%
PM10 Combined B/C blast furnace casthouse fugitives 10.16 tpy 15.04 tpy 48%
PM10 Combined B and C stoves 14.16 lbs/hr. 27.84 lbs/hr. 97%
PM10 BOF baghouse 3.35 lbs/hr. 17.71 lbs/hr. 429%
CO (Carbon Monoxide) BOF electrostatic precipitator 3,057.4 lbs/hr. 7,048 lbs/hr. 131%
VOC (volatile organic compounds) C Blast Furnace Casthouse Baghouse 6.77 lbs/hr. 9.92 lbs/hr. 47%
VOC Combined B/C blast furnace casthouse baghouses 27.0 tpy 49.42 tpy 83%
Lead (Pb) C Blast Furnace Casthouse Baghouse 0.00015 lbs/hr. 0.0077 lbs/hr. 5033%
Lead (Pb) Desulfurization – baghouse 0.000278 lbs/hr. 0.0016 lbs/hr. 476%
Lead (Pb) Combined B/C blast furnace casthouse fugitives 0.000087 lbs/hr. 0.0064 lbs/hr. 7256%
Lead (Pb) Combined B/C blast furnace casthouse baghouse 0.000223 lbs/hr. 0.00753 lbs/hr. 3277%
Manganese (Mn) C Blast Furnace Casthouse Baghouses 0.00256 lbs/hr. 0.042 lbs/hr. 1541%
Manganese (Mn) Desulfurization baghouse 0.00064 lbs/hr. 0.013 lbs/hr. 1931%
Manganese (Mn) Combined B/C blast furnace casthouse fugitives 0.006 lbs/hr. 0.0448 lbs/hr. 647%
Manganese (Mn) Combined B/C blast furnace casthouse baghouses 0.00385 lbs/hr. 0.0597 lbs/hr. 1451%


Severstal Official Website

News article with full text of company’s statement regarding the revised emissions application.


| Dominick DalSanto is an author & dust collection technologies expert, specializing in dust collection systems. With nearly a decade of hands-on working experience in the industry, Dominick’s knowledge of the industry goes beyond a mere classroom education. He is currently serving as sales director at His articles have been published not only on , but also on other industry related blogs and sites. In his spare time, Dominick writes about travel and life abroad for various travel sites and blogs.



Baghouse differential pressure air lines

For baghouses to run efficiently, trustworthy differential pressure readings are required. How can you tell if your DP readings are accurate? What can you do if you suspect you are receiving false readings? This second article in our series on baghouse differential pressure will answer that question. 

By Dominick DalSanto
Baghouse Technology Expert and Sales Director

Why Worry About False Differential Pressure Readings?

As we mentioned in our previous article in this series, having accurate differential pressure readings is essential to operating your baghouse correctly, and efficiently. Operators base almost all of their operational decisions on baghouse DP. If they are given incorrect readings it could result in damage to the system, increase emissions, or even fire and combustible dust hazards.

For example, assume that a unit is giving readings that are lower than they actually are, 3″ w.g. when it really is running at 8″. Because the operator sees such a low reading, he could now make several incorrect operating choices that could have very severe consequences. He may take this low DP reading to mean that his filters are in good condition and do not need to be replaced. With blinded bags, he could begin seeing decreased system performance. Or perhaps his bags could begin producing higher emissions levels thus causing the plant to exceed its air permits, potentially leading to heavy fines and sanctions.

While we cannot detail every possible problem that could arise from this, the point is clear. So what can and maintenance personnel do if they they are receiving incorrect DP readings?

How To Troubleshoot Differential Pressure

Maintenance personnel should examine the DP instruments and determine if there is any obvious problem. Lose connections, backwards connections, and obviously broken gauges are common enough that they should be expected.  Other times, maintenance personnel will need to troubleshoot the instruments to diagnose and remedy less conspicuous issues.

Maintenance personnel will need to determine whether the individual pressure gauges are faulty, or simply have blocked lines coming into them. We recommend the following troubleshooting procedure:

  1. Disconnect all gauges, controller boards, etc., from air lines coming from the collector.
  2. Using compressed air, clean all air lines thoroughly, making sure to blow back into collector.
  3. Using a handheld DP gauge (a normal manometer with flex tube connectors will suffice), hook up the air lines from the collector to obtain the operating DP.
  4. Reconnect the newly-cleaned air lines to the controller board and/or pressure gauge.
    1. If the controller board/pressure gauge reads the same as the handheld gauge did after cleaning the lines, then the controller board pressure sensor and/or pressure gauge is working properly
    2. If the controller board/pressure gauge reads the differently than the handheld gauge did after cleaning the lines, then the controller board pressure sensor and/or pressure gauge is not working
      1. (For the baghouse-mounted DP gauge) Replace with new gauge.
      2. (For controller board) Contact manufacturer about possibility of replacing only the board’s pressure sensor.
        1. If not possible, replace entire board with new controller board.
  5. Remove all unnecessary line splitters, additional lines, and long runs, ensuring all gauges are located as close as possible to the air taps (within 10’ – 15’)
Baghouse differential pressure air lines

Avoid the example here. Avoid splitters and crooked lines.

NOTE: When connecting the new gauge to the clean and dirty side lines, make sure to connect them to the correct ports on the gauge. They should be marked “HIGH” and “LOW”. Just remember, that if hooked up backwards, the needle will pull backwards, instead of giving a positive reading.

How To Prevent False DP Readings

It is important to remember that just because you fixed this problem once, it likely will come back again and again over the life of the baghouse. Inspecting and cleaning/repairing the DP gauges and air lines should be a regularly scheduled maintenance task for all baghouses.Industry best practices should be followed when installing the gauges and air taps to reduce the likelihood of fouling.

Notice in the picture to the right how the maze of lines coming in and out this DP gauge. Best practice is to have just one line from each side of the baghouse coming into the gauge. The lines should run in the most direct and shortest path possible. For this reason, avoid locating the gauges exceedingly far from the unit, such as in other rooms or other floors. Further, to avoid buildup in lines themselves, place the taps near the top corners in each side of the unit.

Baghouse Differential Pressure - Good air lines

A better example of how lines should be run.

Also, using copper line as opposed to plastic or rubber tubing is preferable and we facilitate easy cleaning and is far more durable.

Once You Have Accurate Readings

With your now trustworthy readings in hand you can now begin consider what these readings in conjunction with other available information is telling your about your baghouse.Our next article in this series will examine how to understand your baghouse DP readings and use it to make wise operating decisions.



| Dominick DalSanto is an Author & Environmental Technologies Expert, specializing in dust collection systems. With nearly a decade of hands-on working experience in the industry, Dominick’s knowledge of the industry goes beyond a mere classroom education. He is currently serving as Sales Director at His articles have been published not only on , but also on other industry related blogs and sites. In his spare time, Dominick writes about travel and life abroad for various travel sites and blogs.

Guest Post By Bevin Sequeira
BS&B Safety Systems (Asia Pacific) Pte Ltd. 

Introduction to Dust Explosions

A Dust Explosion is the fast combustion of dust particles suspended in the air in an enclosed location. Coal dust explosions are a frequent hazard in underground coal mines, but dust explosions can occur where any powdered combustible material is present in an enclosed atmosphere or, in general, in high enough concentrations of dispersed combustible particles in atmosphere.

Dust Explosion at West Pharmaceutical Services

Dust explosion at West Pharmaceutical Services, North Carolina took the lives of 6 people in 2003

Dust explosions can lead to loss of life, injury, damage property and environmental damage as well as consequential damage such as business interruption losses.

Dust explosions involve most commonly “dust”, i.e. fine material. This can be the product being handled or it can be produced as the result of the processing. However, in many cases fine dust is present in material that is otherwise too coarse to pose a dust explosion hazard, either as part of the product or generated by attrition during handling or transport. Therefore, while replacing a fine material by a granular one (such as pellets or flakes) will reduce the dust explosion hazards, this may not be sufficient to eliminate the hazards. Similarly, a user of a granular material may process it to a particle size that introduces dust explosion hazards.

Many dust explosions that occur in process plants are relatively small, leading to limited damage. However, under the right circumstances, even small explosions can escalate into major incidents. This is most commonly the case when secondary dust explosions happen. The typical scenario is that a small “primary” explosion raises a dust cloud, often from dust deposited over time on plant surfaces, and ignites the resulting dust cloud. This “secondary” explosion takes place where often people are present, placing them in immediate danger. Secondary dust explosions can form a chain reaction that can run through a facility as long as fuel is present, leading to widespread devastation.


Conditions for Dust Explosion

Dust Explosion Pentagon

There are five necessary conditions for a dust explosion or deflagration:

1. Presence of Combustible Dust
2. Dust suspended in the air at a high concentration
3. There is an Oxidant (typically atmospheric oxygen)
4. There is an Ignition source ( Either Flames & hot surfaces, Spontaneous Ignition, Friction sparks, Static Electricity, Electrical Equipment’s, etc.)
5. Confinement (enclosed location)

Many materials which are commonly known to oxidize can generate a dust explosion, such as coal, sawdust. The dust can arise from activities such as transporting grain and indeed grain silos do regularly have explosions. Mining of coal leads to coal dust and flour mills likewise have large amounts of flour dust as a result of milling. A gigantic explosion of flour dust destroyed a mill in Minnesota on May 2nd, 1878, killing 18 workers at the Washburn A Mill.

To support combustion, the dust must also consist of very small particles with a high surface area to volume ratio, thereby making the collective or combined surface area of all the particles very large in comparison to a dust of larger particles. Dust is defined as powders with particles less than about 500 microns in diameter, but finer dust will present a much greater hazard than coarse particles by virtue of the larger total surface area of all the particles.

Sources of Ignition

There are many sources of ignition and a naked flame need not be the only one: over one half of the dust explosions were from non-flame sources. Common sources of ignition include electrostatic discharge friction arcing from machinery or other equipment or hot surfaces such as overheated bearings. However it is often difficult to determine the exact source of ignition post-explosion. When a source cannot be found, it will often be cited as static electricity. Static charges can occur by friction at the surfaces of particles as they move against one another, and build up to levels leading to a sudden discharge.

Combustible Dust Concentrations:

As with gases, dust is combustible with certain concentration parameters. These parameters vary widely across the spectrum. Highly combustible dust can form a flammable mixture with less than 15 g/m3.

Mechanism of dust explosions:

Imperial Sugar Explosion- Wentoworth Georgia

Imperial Sugar Explosion: Wentworth, GA
17 February 2008: 14 Fatalities

Dusts have a very large surface area compared to their mass. Since burning can only occur at the surface of a solid or liquid, where it can react with oxygen, this causes dusts to be much more flammable than bulk materials. For example, a 1 kg sphere of a material with a density of 1g/cm3 would be about 27 cm across and have a surface area of 0.3 m2. However, if it was broken up into spherical dust particles 50µm in diameter (about the size of flour particles) it would have a surface area of 60 m² This greatly increased surface area allows the material to burn much faster, and the extremely small mass of each particle allows it to catch on fire with much less energy than the bulk material, as there is no heat loss to conduction within the material. When this mixture of fuel and air is ignited, especially in a confined space such as a warehouse or silo, a significant increase in pressure is created, often more than sufficient to demolish the structure.
Even materials that are traditionally thought of as non-flammable, such as aluminium, or slow burning, such as wood, can produce a powerful explosion when finely divided, and can be ignited by even a small spark.


Combustible Dust Explosions Since Imperial Sugar Incident


Dust explosions may be classified as being either primary or secondary in nature.

Primary dust explosions: occur inside process plant or similar enclosures and are generally controlled by pressure relief through purpose-built ducting to atmosphere.

Secondary dust explosions: are the result of dust accumulation inside the factory being disturbed and ignited by the primary explosion, resulting in a much more dangerous uncontrolled explosion inside the workplace.
Historically, fatalities from dust explosions have largely been the result of secondary dust explosions.

Best engineering control measures which can be found in the National Fire Protection Association (NFPA) Combustible Dust Standards include:

• Oxidant Concentration Reduction
• Deflagration venting
• Deflagration pressure containment
• Deflagration suppression
• Deflagration venting through a dust retention and flame-arresting devices
• Spark Detection & Extinguishing Systems




Explosive Materials:Dust Explosions - Bucket Elevator Explosion The following materials are prone to dust explosions.
• Coal
• Fertilizer
• Cosmetics
• Pesticides
• Plastic & plastic resins
• Wood
• Charcoal
• Detergents
• Foodstuffs (sugar, flour, milk powder, etc.)
• Ore dusts
• Metal dusts
• Graphite
• Dry industrial chemicals
• Pigments
• Cellulose

Industrial Equipment:
Typical industrial equipment’s that require explosion protection.
• Dust Collectors
• Dryers
• Cyclones
• Crushers
• Grinders
• Silos
• Pulverisers
• Conveyors
• Conveyor ducts
• Screw conveyors
• Bucket Elevators
• Furnaces
• Hoppers
• Bins


Many reported dust explosions have originated in common powder and bulk solids processing equipment such as dust collectors, dryers, grinders/pulverisers, and blenders. Electrostatic discharges are frequently cited as the ignition source for dust collector explosions, whereas particulate overheating is the most common ignition source in dryer explosions, and friction/impact heating associated with tramp metal or misaligned parts is probably the most frequent ignition source in grinder/pulveriser explosions.

Dust explosions are often exacerbated by propagation through ducting between process equipment, frequently via dust collector pickup and return ducting. Moe widespread use of effective deflagration isolation devices in such ducting would clearly be beneficial in mitigating the damage and injuries from these propagating dust explosions. (See article Dust Collector Fire and Explosion Highlights Need for Combustible Dust Considerations In System Designs)

Secondary dust explosions in processing buildings probably cause the largest numbers of dust explosion fatalities and injuries. One crucial aspect of secondary dust explosion prevention and mitigation is greater awareness of good housekeeping and maintenance practices to prevent particulate leakage from equipment and subsequent accumulations of dust deposits in large areas of the buildings.


About the Author

Bevin Sequeira holds a B.E. (Mechanical) degree & a MBA (Marketing) specializing in business development & enhancement of virgin markets all over the globe. With over two decades of international working experience in the industry, Bevin’s knowledge of the industry spans various sectors like Iron & Steel, Foundry, Chemicals & Fertilizer, Power, Food, Pharma, etc.  He is currently serving as Regional Sales Manager at BS&B Safety Systems (Asia Pacific) Pte Ltd. specialising in Combustible Dust Explosion Protection Systems & Risk Management. In his spare time, Bevin likes to read, travel, socialise & collaborate with business houses for M&A, Management Consultancy, etc.

Diagram of how to install a magnehelic differential pressure gauge on a baghouse dust collector.

Accurate differential pressure readings are essential for efficient baghouse operation. This article outlines the importace of baghouse differential pressure and what baghouse problems it can be used to diagnose. 

By Dominick DalSanto
Baghouse Technology Expert and Sales Director

Baghouse Differential Pressure – Why Important?

Within a baghouse a number of factors must be controlled to ensure the efficient operation of the system at all times. Of these, the most important variable to control is the system differential pressure. This measurement is the key indicator of how the baghouse is operating and the most important factor to consider when diagnosing and troubleshooting issues with the baghouse system.

Over time more and more dirt will penetrate deep into the fibers of a bag being harder to remove. When this happens the bags become blinded or are unable to be adequately cleaned. This causes massive differential pressure increases.

Over time more and more dirt will penetrate deep into the fibers of a bag being harder to remove. When this happens the bags become blinded or are unable to be adequately cleaned. This causes massive differential pressure increases.

Differential pressure (also known as pressure drop or Delta-P) is the difference in pressure between the dirty-air side of the baghouse and the clean-air side. As in the incoming air is pulled through the filter media (i.e. filter bags) vacuum is lost, resulting in the air entering the baghouse having a weaker vacuum than the air exiting the baghouse. For example, let’s say that the system fan is pulling 10″ w.g* of vacuum pressure. When the dirty air comes into the baghouse the pressure is at 3.5″ w.g.* of vacuum, but after entering into the baghouse and passing through the filters the pressure rises to 10″ w.g.. This means the pressure drop across the baghouse is 6.5″ w.g. (Note: This example assumes a clean-air side fan or negative pressure system)

Differential pressure readings are used to determine a number of things about the operation of a baghouse system, such as filter bag condition,  and structural problems with the unit, (airlock and conveying system condition and door seals condition among other things). Furthermore, a high system differential pressure usually indicates that the system is not running efficiently and therefore is incurring higher operating costs than it should under optimal circumstances. The following problems can be diagnosed from observing the system differential pressure:

Filter Bag Condition

  1. Bags are blinded off
    • Dirty bags will become more resistant to airflow thus causing the force to push the air through them to rise.
  2. Bags have holes in them
    • This will create a path of less resistance for the air to flow through leading to lower pressure drop
  3. Bags are not installed properly
    • See above

Structural and Sealing Issues

  1. Leaks within the structure
    • Common leak areas include airlocks, welds, joints (especially panelized construction units), and door seals
  2. Airlock leaks
    • Common around flaps,rotars, gaskets and connection points.
  3. Conveying system leaks
    • Common at connection point to hopper/airlock, holes in ductwork structure, etc.
  4. Doors and hatch sealing
    • Gaskets on all doors and hatches, including viewports. Also includes making sure all doors have sufficient fasteners (i.e. bolts) to secure the door/hatch securely to form a tight seal.
Diagram of how to install a magnehelic differential pressure gauge on a baghouse dust collector.

Diagram of how to install a magnehelic differential pressure gauge on a baghouse dust collector.

Why High Differential Pressure Means Higher Operating Costs

Controlling your baghouse differential pressure is required to get the maximum performance and efficiency from your system. If your system is running at a high differential pressure it will inevitably cost more to operate, have lower performance and experience more downtime. High DP means the system fan needs to work harder to pull the same amount of airflow throughout the system. IF DP starts to rise above the recommended levels,  maintaining the same level of draft (i.e. suction) at all of the systems pickup points will prove difficult. This will lead to much higher energy costs to run the system fan at high speed and can if over taxed lead to premature fan/motor failure. If the system fan is not adjusted to compensate for the higher differential pressure, the system will lose draft at all of its pickup points. This will mean less performance from your system and inescapably cause problems for your facility process whatever it maybe, especially so for certain industries that are more dependent on the dust collection system as part of the process such as cement, powdered metals, chemical processing, etc. In the end, this will result in the process being shutdown or even a shutdown of parts or the entire facility until the system is running again.


Clearly, it is of vital importance for maintenance staff and operators to keep close watch on dust collection system differential pressure. If system DP is higher than recommended it can be a indicator of several potentially serious issues, ranging from blinded bags, to holes in the structure to poor seals, etc. Accordingly, obtaining accurate differential pressure readings is vital to have an accurate picture of what is going on within your baghouse system. But what can you do if your equipment is giving you suspicious or even false readings? How can you determine when your DP gauges and controls are sending false readings? These questions will be in the following article in the series: Baghouse Differential Pressure – How To Troubleshoot False Readings


* “w.g. stands for inches of water gauge, that is vacuum pressure as measured in inches of water (sometimes mercury) as in a magnehelic gauge.


| Dominick DalSanto is an Author & Environmental Technologies Expert, specializing in Dust Collection Systems. With nearly a decade of hands-on working experience in the industry, Dominick’s knowledge of the industry goes beyond a mere classroom education. He is currently serving as Sales Director at His articles have been published not only on , but also on other industry related blogs and sites. In his spare time, Dominick writes about travel and life abroad for various travel sites and blogs. Corp

By Dominick DalSanto

October 28th, 2012 | The process of selecting a baghouse filter supplier for your next set of replacement filters might seem like a simple task. You might think that all you need to do is call them up, tell them your model number and you will be set. But is it really that easy? Can you always rely on just any supplier to get you the right bags, at the best price, every time?

Outlined below are several things that will help you to find the right supplier for your next set of replacement baghouse filters. Going into the filter quoting process armed with this information will enable you to secure the products at a fair price. These are the three key points to keep in mind when searching for your next set of replacement bags.

Have The Correct Information Before You Call

Most people begin their search for replacement bags with only the most basic of information, if any at all. At times all they have is some supplier’s arbitrary product number from their last set of bags, or a serial number from the side of their baghouse. The fact is that there is no central database of baghouse filters out there for your supplier to check. The majority of these product numbers are from their respective manufacturers and only for their internal record keeping/branding.

In order to receive an accurate replacement baghouse filter RFQ more information will be needed. While you may not have easy access to all of this information when sourcing quotes, the more you have the easier it will be for the supplier to give you an accurate quote. Information to have on hand includes:

Dust Collector Type – What kind of filters, cleaning system type, etc.

Filter Measurements – Physical dimensions of the filters

  • Length
  • Diameter
  • Flat-Width

Filter Construction – This differs based on how the bags are installed in the baghouse

  • Top (Snapband, Strap, Raw Edge, etc.)
  • Bottom (Snapband, Disk, Compression, etc.)

Filter Fabric – The material along with any coatings, finishes or membranes

  • Fabric (Polyester, PPS, Cotton, Fiberglass, etc.)
  • Coating/Finish (Singed, fire-resistant, etc.)
  • Membrane (PTFE, etc.)

Special Considerations – Special added features needed only on certain bags

  • Antistatic wires
  • Support rings

It is also good to include a general overview of the process the filters are used for. This would include air temperature, product to be filtered, alkali or acidic level, combustibility of the dust, etc. You should also including information about how often you replace your filters, system pressure drop, filtering efficiency. While not absolutely necessary, this information will allow a good supplier to offer suggestions for different products that might improve the operation of your system. (SEE BELOW)

Remember to have as much of this information on hand before you begin contacting filter suppliers. If you are not sure about some of these specifications try to get as much as information as possible and then a good filter supplier can help you to find the rest.

How to Choose a Baghouse Filter Supplier

There are hundreds of filter suppliers, manufacturers, and sales reps out there to choose from. Finding one that will get you the best product and provide you with the best service for a fair price is no easy task.

Often times, companies portray themselves as “dust collection experts” when in reality they are only sales reps that have little real knowledge of how these complex industrial systems operate. You will want to consider their level of experience in the industry. Companies with real-world experience in the field are able to provide a vastly superior service than the rest. For example, an experienced supplier will be able to not only take your order, but also offer suggestions on how to improve your dust collector operation by offering tips on installation methods, maintenance procedures, and other ways to increase system efficiency, and extend bag life. They also will be able to offer suggestions for different products (such as new fabrics, pleated elements vs. traditional bags, etc.) that could reduce costs and increase efficiency.

Additionally, you should look into the reliability and trust-worthiness of the company before doing any business with them. This can include asking for references from their previous clients, reviewing their return policy, and any guarantees they may offer on their products.

Additionally, you may wish to seek out a supplier that also offers baghouse filter replacement services as well. Having qualified baghouse technicians install your new baghouse filters often is a better choice than using in-house personal. Many times filter suppliers will provide you with a far better price for your filters if you also use them for the service work. (For more information on how to find a capable baghouse service provider please visit for more information.)

The knowledge an experienced supplier can provide is invaluable. Take advantage of this by seeking out a trust-worthy, and experienced supplier?

Do Not Forget About Filter Replacement Services!

While many facilities often elect to use their own in-house labor to install their replacement baghouse filters, or they purchase the bags themselves and then contract out the installation work to another company. However, there are large savings to be had by purchasing your filter bags from a company that also performs baghouse filter replacement services. In a future article we will discuss additional reasons why it is advantageous to have experienced baghouse maintenance specialists perform your filter replacement. But for now, it will suffice to say that savings of upwards of 5% to 10% can easily be had by sourcing your filter bags and replacement service from the same company. Truly, not something to be overlooked!


Sourcing a quote for replacement baghouse filters is not a task to take lightly. The difference between a capable filter supplier and a poor one is dramatic. While it may not always be easy to find a good supplier, by following the suggestions in this article you can find one that can provide you with the products you need for a fair and reasonable price.


| Dominick DalSanto is an author and environmental expert specializing in baghouse dust collection systems. With nearly a decade of hands-on working experience in the industry, Dominick’s knowledge of the industry goes beyond a mere classroom education. He is currently serving as marketing director at His articles have been published not only on , but also on other industry related blogs and sites. In his spare time, Dominick writes about travel and life abroad for various travel sites and blogs.



1. For help see article “How to Chose The Correct Baghouse Filter.”
2. A good filter supplier should allow you to send in a sample of your current bags to ensure they are measured correctly. This can be an extra bag, or one from the baghouse (you can remove it and cap off the spot where it was to prevent leaks).




Environmental groups claim the 1625 MW coal-fired plant in La Grange, Texas is exceeding PM2.5 emissions limits due to outdated dust collectors and poor operating practices.

By Dominick DalSanto

July 20, 2012 News | Environmental groups in Texas are suing one of the largest coal-fire power plants in the state, alleging the plant is violating its air pollution permits and emitting excess dust pollution. The Fayette Power Project located in La Grange, Texas, a 1,625 megawatt power plant located about 60 miles west of the state capital of Austin was served a notice of intent by the Environmental Integrity Project (EIP).

Excessive emissions often occur when plant operators fail to stay within require operating parameters (e.g. running the system to hot thus causing damage to the filter bags, placing too large of a load on the baghouse, etc.) or when they are using out-of-date equipment that is well past its recommended service life.

The EIP alleges LCRA (Lower Colorado River Authority the majority owner and operator of the plant) is in violation of its air pollution permits from the Texas Commission on Environmental Quality (TCEQ), specifically the limits on particulate matter (PM2.5), claiming that the plant uses antiquated electrostatic precipitators for dust collection instead of newer, more efficient baghouse filters.

The EIP, which is representing the Texas Campaign for the Environment and other environmental groups, previously filed six claims against LCRA, two were withdrawn, three others were dismissed by the courts, leaving only this issue to continue to the discovery phase in a Houston federal court. LCRA says that claim “involves unfounded allegations” and the costs of the suit “will eventually be passed on to ratepayers.”

“We’ve discovered what we believe are egregious violations of the air pollution permit for the power plant and that harms public health, pollutes the air that we all breath,” said Ilan Levin, the Associate Director of Environmental Integrity Project.

LCRA General Manager Becky Motal flatly denied the charges, and claims the environmental groups are harassing them despite being “one of cleanest coal-fired plants in Texas”. “This notice of intent to file yet another lawsuit with similar allegations as in a previous suit is completely unwarranted and harassing,” Motal said in a press release after they learned of the suit. “FPP [Fayette Power Project] is one of the cleanest and most efficiently operated coal plants in Texas, and I am proud of the conscientious, environmentally responsible work our employees do providing electricity to more than a million people in Central Texas.”

Texas Vs. The EPA – The Origins of the Battle

Currently, the Fayette plant operates under what is known as a “flexible permit”. meaning it allows for exceeding emissions levels in certain areas if they are made up for by better than required performance in other areas. The flexible permits are issued by the Texas Commission on Environmental Quality, the state agency charged with regulating and enforcing environmental laws in Texas. The EPA (the federal agency with ultimate authority over environmental law in the US) ruled several years ago that the flexible permits did not meet federal standards and were illegal. The situation between the EPA and the TCEQ plays a part in the case against LCRA.

Environmental groups are suing the Fayette Power Project located in LaGrange, Texas saying it violates its air permits, and needs to install new air pollution control equipment, including new more efficient baghouse filter systems to replace older, less efficient ESPs.

According to Ilan Levin the Associate Director of Environmental Integrity Project, the LCRA is in the process of obtaining a new permit to increase levels for particulate matter emissions from the state board. “We are trying to enforce the permit that is currently on the books,” he says. “Now EPA has already ruled that those flexible permits are illegal — that they don’t meet federal standards. And we agree with that. But nonetheless that’s the permit they have. And what we’ve found is that they’re not even meeting the limits in that awful flexible permit.”

In response Motal of LCRA said “FPP complies with all permit limits, and in most cases emissions are well below levels set by federal and state authorities. The authority says that the plant “has long been recognized as one of the cleanest coal-burning power plants in the state.”

ESPs vs. Baghouses – “Outdated ESPs not working very well”

In March 2011, the plant installed air scrubbers on Unites 1 and 2 at a cost of about $400 million. LCRA and its partner Austin Energy (which jointly owns Unites 1 and 2 with LCRA) says the air scrubbers now remove more than 95% of sulfur dioxide emissions. Prior to this local farmers accused the plant of contributing to the degradation of their surrounding farm land due to acid rain caused by the plant’s SO2 emissions. *

While environmentalists welcome the installation of the SO2 scrubbers, they believe the plant needs to do more regarding particulate matter (PM2.5 dust particles 2.5 microns in size and larger) emissions, which are linked to asthma, heart disease, premature death, and other respiratory conditions. The core of the current lawsuit claims the plant exceeded federal limits for PM2.5.

They say the plant needs to replace its outdated ESPs with newer, more efficient baghouse filter systems. “The LCRA Fayette Power Plant doesn’t have baghouses,” Levin says. “Instead they’ve got thirty-year old electrostatic precipitators or ESPs and those aren’t working very well. In fact, what we’ve found is that the really high levels of particulate matter pollution are happening when they start those coal-fired boilers up. And they are often in start-up mode for hundreds of hours per year.” Levins says that the LCRA doesn’t turn on their pollution controls that would capture particulate matter during those start-ups. “And so during start-up, the public is exposed to excessive and very dangerous levels of soot or particle pollution,” he says.

Today, filters (commonly known as baghouses or fabric filters) are used by plants to prevent the escape of particulate matter from their stacks. these are help in most opinions to be more efficiency than ESPs, which use electrodes to charge incoming dirty air that then passes by large electromagnetic plates that collect the charged dirt particles.

No Amicable Settlement in Sight

While both sides claim to be working to ensure a clean source of electricity for the surrounding area, it does not seem likely that the two parties will work things out by themselves. “The answer to the question ‘Why now?’ is that we feel like we have no choice. We’ve been talking to LCRA or trying to talk to LCRA for a couple of years,” Levin says. “We haven’t made any headway. We’re only bringing this lawsuit because the state regulators and the federal regulators, that is to say the Texas Commission on Environmental Quality and the EPA, are not enforcing the law.”

About The Author:

| Dominick DalSanto is an Author & Environmental Technologies Expert, specializing in baghouse filter systems. With nearly a decade of hands-on working experience in the industry, Dominick’s knowledge of the industry goes beyond a mere classroom education. He is currently serving as Online Marketing Director & Content Manager at His articles have been published not only on , but also on other industry related blogs and sites. In his spare time, Dominick writes about travel and life abroad for various travel sites and blogs. Born in San Bernardino county California, raised in Chicago Illinois, he currently resides in Buenos Aires, Argentina.


See Article Pecan Growers Blame Coal-Fired Plant For Killing Crops

Previous Articles on Air Permitting:

By Dominick DalSanto

October 3, 2012 – | Recently, the EPA has been busy issuing new air pollution regulations (Cross-State Air Pollution Rule, Cement MACT, Mercury MACT, etc.) and tightened several exiting ones (NESHAPs, NAAQs, etc). With the new standards, and revisions to existing ones, many formerly compliant facilities may not find themselves no longer able to meet their existing air permits. In addition, some facilities will need to complete the application process again for new permits based on the new standards. This process can be exceedingly difficult, due to the complexity of the regulations. Many facilities end up getting lost along the way, potentially costing them millions of dollars in the process.

A while back had the opportunity to speak with Trinity Consultants, an international firm that specializes in assisting industrial companies with air quality regulatory compliance challenges, about the coming changes in the regulatory scene and how companies can avoid getting lost in the process. The following are some excerpts from that interview that we feel will be helpful for our readers.

Interview with Trinity Consultants

What would you say is the most difficult section of current clean air regulation for industry to come into compliance with?

“At present, the new National Ambient Air Quality Standards (NAAQS) and associated U.S. EPA dispersion modeling requirements for demonstrating compliance with nitrogen dioxide (NO2), sulfur dioxide (SO2), and fine particulate matter (PM2.5) are the most difficult provisions of the clean air act regulations for new or modified facilities.  U.S. EPA has also promulgated additional challenging requirements that affect specific industries or specific source types including National Emission Standards for Hazardous Air Pollutants (NESHAP), Maximum Achievable Control Technologies (MACT), and New Source Performance Standards (NSPS) for industrial-commercial-institutional steam generators (boilers), electric utility steam generating units (utilities), portland cement manufacturing, and others.”

What problems do you encounter with regards to dust collection/particulate matter (PM2.5)emissions?

“Dust collection, capture, and control is an important consideration for compliance with the PM2.5 NAAQS as well as compliance with the new NESHAP, MACT, and NSPS noted above. ”

One of the “scariest” new regulations is the Mercury MACT; what role will baghouses play in meeting these new standards?

“Most technologies for collecting mercury emissions involve the use of a baghouse. The most common include injecting a material to absorb the mercury in the airstream, usually activated carbon or a proprietary sorbent compound, which then needs to be collected from the airstream just like any other particulate matter would be, by the baghouse. In some cases the only way to handle this increased particulate load is to upgrade the baghouse. This could mean replacing the bags with more efficient PTFE membrane bags, expanding the baghouse (either by added more compartments, using a larger baghouse, or by switching to pleated baghouse filter elements).”

What problems do you encounter frequently with the regulatory process that are the most frustrating?

“We have clients that have had to cancel proposed capital expansion projects due to the economic and/or operational infeasibility of complying with the new NAAQS provisions for PM2.5, SO2, & NO2.”

What can companies do when they feel overwhelmed by the often complex permitting process to make sense of the situation?

“Our clients frequently request staff from Trinity Consultants to train, advise, or develop strategic guidance for their environmental, management, operations, and/or legal staff on the complex environmental topics or have Trinity Consultants directly assist with their permitting and compliance needs.”

What do you feel is the most important thing for companies to keep in mind with regards to compliance issues?

“Stay up to date (fresh, timely) on the regulatory rule changes affecting their industry.  Participate in industry associations or work groups that focus on environmental requirements for your industry.  Companies can also find timely updates, regulatory notices, and training courses at  We also suggest that companies subscribe to Trinity Consultants’ periodic publications which include Environmental Quarterly and eNews at

How do these previously mentioned regulations come into play with regards to dust collection? (National Emission Standards for Hazardous Air Pollutants (NESHAP), Maximum Achievable Control Technologies (MACT), and New Source Performance Standards (NSPS) for industrial-commercial-institutional steam generators (boilers), electric utility steam generating units (utilities), portland cement manufacturing, and others)

“For existing utility sources, the 0.03 lb/MMBtu limit should easily be met with a good ESP, and does not force you into a baghouse – our understanding is the crossover point may be about 0.005 lb/MMBtu filterable.  For new utility sources, the limit is very low and could only potentially be met with a baghouse.   

For cement plants, ESPs are likely a thing of the past and existing baghouses will likely need new filter media or polishing baghouses.  There are many retrofit projects currently being pursued.  With the new NSPS, lower than 0.002 gr/dscf bags are being evaluated.  Getting suppliers to guarantee PM emissions limits on new units that meet the standards will be very challenging.  In some places, two bags may be needed in series, one for lime injection providing some scrubbing effect and then a final bag house.  Meeting the PM limit is very challenging for the cement industry, requiring periodic maintenance program improvements, even a single bag leak can take you out of compliance.   

Industrial-commercial-institutional boiler considerations:   
For solid fuel-fired boilers, it appears that fabric filters will be required (whenever the rule becomes effective).  At this time, it’s impossible to tell what the reconsideration will do as many companies are looking to expand it. 
For liquid fuel-fired boilers, fabric filter may be an option.  We expect companies that installed a new baghouse would have used a BLDS since it appears to be preferred over a COMS.  We expect some companies will convert to natural gas instead of upgrading their solid and liquid-fired emissions controls.”

What specific problems do you find that companies have gaining compliance with regards to their baghouse?

“Opacity limits with short-averaging periods are a big problem for ESPs – almost any ESP on a solid fuel unit cannot run 100% compliance, though 99%+ is possible.  A baghouse can run essentially 100% compliance.  Since they all have COMS you record every hour.  PM CEMS are a big problem as their accuracy is suspect – back-to-back testing with Method 5 and a PM CEMS can give very different answers.

For the cement industry, the greatest challenge in meeting the new PM limits, other than the limits being low, is the related requirement to meet the limits with a PM CEM.  There is virtually no data of this type in the industry and the monitoring equipment is complex.  Therefore, there is significant uncertainty at to whether the limit is achievable, day in, day out. 

According to the Council of Industrial Boiler Owners (CIBO) the level of emission reduction for industrial-commercial-institutional boilers has not been demonstrated to be achievable by industrial applications, and may only be achievable on a consistent basis with the use of new technology not commonly used in industrial applications.  Electrostatic precipitator suppliers and bag house suppliers both indicate that this new standard is not achievable with the exception that the type of exotic filters used for clean rooms in food production and some pharmaceuticals may be applicable but at exorbitant cost.”

What aspect (or specific regulation or set of regulations) do you feel needs to be revised or reformed the most to make the regulatory process more conducive to industrial growth, while still providing protection for our environment?

“I believe EPA and state agencies need to revise or reform their dispersion modeling methodologies and/or tools to more realistically assess compliance with the new 1-hr NAAQS.”

Would you say that current regulation is hampering companies’ efforts to expand their operation?


Advice for Companies

When working with a client to achieve overall compliance of their facility with applicable regulations, what advice or warnings do you give to them regarding the proper operation, and maintenance of their baghouse system?

“Periodic baghouse maintenance programs for many plants will need to be improved. There is a lot facility operators can do to make their baghouses run more efficiently.”

How important is it for plants to make sure their dust collection system is functioning properly?

“It will be very important to demonstrate continuous compliance with the more stringent regulatory requirements.”

Do you believe that it is in a facilities best interest to upgrade outdated and undersized dust collection equipment? In your experience (expert opinion) do you feel that it is worth the investment in capital for the potential benefits?

“Upgrade decisions will be required on a facility by facility basis but in many instances, upgrading of equipment will be necessary / required.”

What percentage of your clients would you say are having problems with their baghouse system that are causing them to be out of compliance with clean air regulations?

“By and large, our clients are in compliance with clean air regulations (continuous compliance is not an option for business risk mitigation).  However, the recent stringent regulations presents significant challenges and our clients are actively pursuing and developing solutions to implement in the next year or two.”


About Trinity Consultants: Founded in 1974, Trinity Consultants is an international firm that specializes in assisting industrial companies with air quality regulatory compliance challenges.  Trinity also provides professional training, environmental modeling software, EH&S information management solutions, and EH&S staffing services.  Environmental professionals can subscribe to Trinity’s free Environmental Quarterly publication at


| Dominick DalSanto is an Author & Environmental Technologies Expert, specializing in Dust Collection Systems. With nearly a decade of hands-on working experience in the industry, Dominick’s knowledge of the industry goes beyond a mere classroom education. He is currently serving as Marketing Director at His articles have been published not only on , but also on other industry related blogs and sites. In his spare time, Dominick writes about travel and life abroad for various travel sites and blogs.


A massive fire and explosion in the dust collection system of a New Hampshire wood pellet manufacturer demonstrates the need for adequate system design to prevent combustible dust explosions in general industry.

By Dominick DalSanto
Baghouse Technology Expert and Sales Director

May 16 2012 – Editorial | On October 20 2011, a combustible dust fire began in the wood pellet cooler, most likely caused by a spark or ember from the pellet hammer mill. The fire then spread through the ductwork throughout the plant, eventually reaching the dust collector causing it to explode. When the collector exploded, the explosion vented through the baghouse’s explosion vents into adjacent storage silos setting them ablaze further spread the fire throughout the plant. More than 100 firefighters and emergency personnel from at least 14 towns worked for over 15 hours to put out the blaze.

The OSHA report outlines specific areas where the plant lacked adequate spark detection devices, fire suppression systems, and explosion venting/protection within the dust collection system. The fact that the plant had been cited by OSHA for several of the same issues previously after a 2008 incident, led to OSHA assessing total fines of $147,000.

Examining what went wrong in this incident highlights the need for diligence on the part of plant management and operators regarding the dangers of combustible dust.

What Went Wrong?

The October 20 2011 fire and explosion at the Jaffrey, NH plant was not the first combustible dust related incident at the plant. In 2008 the plant experienced a similar fire and explosion that caused more destruction than the most recent one. After completing its investigation, OSHA at that time fined the plant over $100,000 for safety violations that led to the fire. Subsequently, the plant, in an attempt to prevent another such occurrence, “retained engineers and consultants, and spent over $2 million on various improvements to enhance worker safety at its Jaffrey facility” according to a release from the company. This apparently including the installation of some explosion isolation devices in the ductwork (Rembe explosion isolation device) and installed explosion protection (explosion vents) on the baghouse. However the company’s effort and expense failed to prevent another incident from occurring.

Fire fighters work to put out a massive blaze caused by a destructive combustible dust fire and explosion at the New England Wood Pellet Company's Jaffrey, NH facility.

Fire fighters work to put out a massive blaze caused by a destructive combustible dust fire and explosion at the New England Wood Pellet Company’s Jaffrey, NH facility.

The OSHA report is quite thorough in its description each poorly designed, installed and operated part of the dust collection system either caused or intensified fire and subsequent explosion.

For example the report cites the plant for 2 main offenses. The first one is regarding poor housekeeping throughout the plant that led to large accumulations of combustible wood pellet dust forming on top of machinery (such as the pellet cooler where the fire began) and on elevated surfaces such as overhead rafters, ceiling joists, troughs, etc. Secondly, and more seriously, the plant was cited under the General Duty Clause of the OSHA Charter* for failing to take reasonable steps to prevent a combustible dust fire/explosion from occurring. OSHA cited several industry standards such as the National Fire Protection Association building code that the plant failed to heed in the design and construction of the plant’s dust collection system.

Ductwork Lacked Sufficient Spark Detection, Fire Suppression, or Explosion Isolation Devices

A major oversight in the ductwork system, was the lack of appropriate spark detection, fire suppression or fire isolation devices on all of the ductwork between the various machines throughout the plant. For instance, OSHA reported that the connecting ductwork between the pellet hammer mills, the pellet cooler, the bucket elevators storage silos and most of the dust collectors in the plant had no spark detection system, fire suppression system, or explosion isolation devices installed. The only control device the plant had was an explosion isolation device on the conveying duct between the pellet cooler and the pellet cooler baghouse. However, the device did not function properly and allowed the fire to propagate further downstream into the baghouse.

NFPA 664 (2012) Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities: 8.2.1. and Hazard Determination – Conveying systems with fire hazards should be isolated to prevent propagation of fire both upstream and downstream (OSHA isolation can mean spark detection and suppression). Prevention of Fire Extension: When limitation of fire spread is to be achieved the following criteria shall be demonstrated…(4) Particulate processing systems (dust collection systems) shall be designed, constructed, equipped and maintained to prevent fire or deflagration from propagating from one process system to an adjacent process system.

Additionally, the ductwork was not engineered and/or constructed to sufficient strength to withstand the maximum anticipatable explosive pressure resulting from a conflagration involving its intended payload (combustible wood dust). This led to the duct bursting open, releasing the explosion into the plant near firefighters and may have been a contributing factor in the fire by-passing the isolation device.

NFPA 664 (2012), Sets forth alternative safety criteria for ducts with a deflagration hazard, to ensure that the ducts are builds with a sufficient strength and with appropriately sized/located protection devices to handle the maximum expected pressure generated by a dust explosion. 

Baghouse Was Not Adequately Protected Against Explosion Hazards

The plant recently installed explosion vents on the baghouse explosion vents.* However, the design and installation of the explosion protection on this particular baghouse may actually made things worse than if there had been none at all.

When the fire reached the baghouse and caused the finely dispersed dust to ignite, the resulting pressure and fireball should have been vented outside the building. However, the explosion vents on the baghouse faced the direction of adjacent storage silos (containing wood dust). When the explosion was vented out it ignited the storage silos resulting in a major portion of the fire.

Additionally, OSHA’s investigation showed that the baghouse lacked an explosion suppression system, was not designed and/or constructed to withstand the maximum unvented pressure of a combustible dust explosion, and in the absence of proper explosion protection, was located indoors.

As a result of these failures, when the reached the dust collector, the resulting explosion: blew the dust collector’s door off its hinges, creating a missile hazard, blew backwards into the duct, which burst open, and blew out the dust collector’s exhaust muffler and roof stack, causing the pressure/deflagration to be vented inside the building near responding firefighters.

NFPA 664 (2012) Requires an outdoor location for the dust collectors with fire or deflagration hazards, unless they are equipped with one of the following: (4) listed deflagration suppression system, (5) deflagration relief vents with relief pipes extending to safe areas outside the building and the collector meets the strength requirement of this standard (i.e. built with sufficient strength to withstand the maximum expected explosions pressure). NFPA 664 (2012) requires dust collectors with deflagration hazards be equipped with an appropriate-sized explosion suppression system and/or explosion relief venting system designed per NFPA 68 (Explosion Protection by Deflagration Venting) and NFPA 69 (Explosion Prevention Systems), and also that such dust collectors be built to design strength that exceeds the maximum expected explosion pressure of the material being collected. NFPA 69, 12.1.2 requires “Piping, ducts, and enclosures protected by an isolation system shall be designed to withstand estimated pressures as provided by the isolation system manufacturer”. NFPA 69, “System Verification” requires that systems shall be verified by appropriate testing under deflagration conditions to demonstrate performance.”

These design oversights directly increased the destructive power of what had until then been only a dust fire in the ductwork.

Lessons Learned From Wood Pellet Company Dust Explosion

Simply put, this disaster was bound to happen due to glaring design and/or construction flaws throughout the entire system.

The fact that multiple similar incidents have occurred at the facility demonstrates that the dust collection system, and perhaps even the entire production process requires modification to ensure this kind of incident does not occur again.

Under OSHA’s National Combustible Dust Emphasis Program, OSHA inspectors are on heightened alert for any combustible dust hazards in facilities in all industries. Indeed OSHA is under a federal mandate and its has as its own goal to issue a comprehensive combustible dust standard for general industry. In the meantime, OSHA has been citing plants under the general duty clause for having combustible dust hazards. In most cases, OSHA is informally requiring general industry to conform to the NFPA’s guidelines for combustible dust hazards. As seen in this case following they suggestions would have prevented this kind of incident from occurring.

Therefore, we can take away from this the need to be conscientious and proactive regarding combustible dust hazards in your facility. As we have seen, being reactive will simply not do.


* OSHA General Duty Clause (a) Each employer — (1) shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees; (2) shall comply with occupational safety and health standards promulgated under this Act.

*  Baghouse Explosion Vents – Explosion vents are a form of explosion protection used on baghouses. During normal operation the vents are closed and maintain an air-tight seal. However, if an explosion occurs within the baghouse, the vents are designed to “strategically fail” being the weakest part of the baghouse structure, thus allowing the pressure from the explosion to vent out and away from other combustible materials and workers.


| Dominick DalSanto is an Author & Environmental Technologies Expert, specializing in dust collection systems. With nearly a decade of hands-on working experience in the industry, Dominick’s knowledge of the industry goes beyond a mere classroom education. He is currently serving as Sales Director at His articles have been published not only on , but also on other industry related blogs and sites. In his spare time, Dominick writes about travel and life abroad for various travel sites and blogs.