Combustible Dust: An Overview

We start this article out by taking you into a galaxy far, far away.  Actually, technically speaking, we’re only going into our back yard, to the center of the Milky Way Galaxy.  You may be asking, why do I want to travel there, as I'm only in need of combustible dust safety information or FR clothing?  Well, because Mother Nature often demonstrates her powerful ways to us, if we only observe.

 
Infrared View of the Milky Way Galaxy from NASA's Spitzer Space Telescope

Our Milky Way is one dusty place and it is essentially the building block for stars, planets and life!  Even the the Bible discusses dust, "In the sweat of thy face shalt thou eat bread, till thou return unto the ground; for out of it wast thou taken: for dust thou art, and unto dust shalt thou return." Genesis 3:19

Dust is mesmerizing, powerful and creative! 

Cosmic dust is everywhere and it's falling into Earth's atmosphere each day.  It’s so dusty in space that the Milky Way's center can’t be seen unless the National Aeronautics and Space Administration (NASA) utilizes infrared technology from the Spitzer Space Telescope.  Within the clouds of gas, flame, heat, and dust, new stars are created.  This same powerful force is essentially what takes place right here on planet Earth during a combustible explosion.  There are definitely additional facets to forming a star, but in the text below, we will show you how the two are linked.  Unfortunately, it’s not a new star that’s typically formed on Earth when there’s a combustible explosion.  Instead, our explosions often involve people getting injured or equipment being damaged or destroyed by combustible dust explosions in industrial facilities.   

Well, we hope you enjoyed your space travel!  We know it's been a short ride, and we would love to dive deeper into the subject.   However, we are a safety company specializing in PPE, so our space journey must end... We are officially back on planet Earth now, which means we’re on a planet not equipped to deal with dust, heat, and explosions like our galaxy’s galactic center does.  Instead, we see dust explosions wreak havoc across numerous U.S. industries.  And, instead of a new start, most involved in a combustible dust explosion face life-threatening injuries.  

Combustible Dust Injuries

Over the past decade, the total number of catastrophic fires and explosions caused by combustible dust has been significantly increasing.  In the past 25 years, at least 281 major combustible dust incidents were reported.  And, unfortunately, where there are incidents, there are injuries and fatalities.  Those almost 300 incidents over the past 25 years have killed 119 and injured 718 workers, in addition to destroying many industrial facilities.

According to OSHA, approximately 900 workers have been injured or killed since 1980 by combustible dust occurrences.  Due to these numbers, OSHA has placed significant emphasis on combustible dust hazards for some time now, which is evident in the timeline shown below.  

Fiery Dust Explosion

Combustible dust is a strange and dangerous phenomenon that impacts a wide variety of industries, and workplace safety regulations are only just beginning to address them.  The future does look brighter, though, concerning the new NFPA 652 standard going into effect in September 2020.  It will act as a lighthouse, or better yet, a galactic center, guiding all users on proper safety measures needed when combustible dust is a possibility.  There are now specific strategies and tactics in place to avoid harmful combustible dust accidents, and we’ll cover everything you need to know below. 

What is Combustible Dust? 

Combustible dust is a fine particle material capable of igniting and exploding when mixed with oxygen.  Alberta’s Occupational Health and Safety Code officially defines it as a “dust that can create an explosive atmosphere when it is suspended in the air in ignitable concentrations.”  As little as 1/32" of dust thickness has the potential to ignite.  Simply put, any solid material that can burn in air will do so with violence and velocity and increase with an ever-increasing degree of separation of the material.

A Fine Particle 

Dust is created as a result of mechanical processes where material is crushed, cut, grounded, shaped, handled, processed, polished, or transported.  This dust becomes a hazard when mixed with oxygen and an ignition source; most any material has a risk to catch fire and explode.  Typically, however, explosions originate from larger solid forms such as wood, metals, or inorganic non-metal materials -- and some of these materials may even be non-flammable until they reach their dust form.  

Production and processing workplaces are often environments where dust accumulates.  Here are some areas where dust tends to build up:  

• Dust Releasing Operations: cutting, dumping, grinding, mixing, sifting 
• Mechanical Processes: heating, spraying, pouring, ventilation
• Confined Areas: vats, boilers, ventilation systems, small rooms
• Surfaces: elevated areas, rafters, suspended ceilings
• Open areas: packaging, floors, horizontal surfaces
• Hidden areas: beams, ducts, piping

Examples of dust materials, whether flakes, fragments, or bits, that pose a distinct combustion danger include: 

• Agricultural products, like sugar 
• Chemicals, like sulfur
• Metals, like magnesium

We’ve only touched on a few of the materials found on the combustible dust list.  You’ve probably heard the saying, a picture is worth a thousand words, so please take a look at the picture of a poster created by the Occupational Health and Safety Administration (OSHA) that gives a more extensive list of combustible dusts.

Combustible Dust List 

What industries have combustible dust hazards?

Whenever we start diving into this subject, someone will ask the question: what industries have combustible dust?  Let’s put it this way: most manufacturing locations can easily become dirty environments, and rather quickly, which ultimately means dust is present.  Any workplace where materials are transported and processed will likely result in the creation of dust, especially if there’s harsh cutting, crushing, sifting, or screening of dry materials taking place.

Here is a quick snapshot of each ranked industry that is likely to experience potential combustible dust:

1. Food Products – food manufacturing, grain milling, bins, grain elevators and confined silo spaces, flour used for baking, equipment used to pulverize sugar
2. Lumber and Wood Products – pulp and paper, sawmilling
3. Chemical Manufacturing – dyes, fertilizers, pharmaceuticals
4. Primary Metals – processing aluminum, recycled metals
5. Rubber and Plastic Products – rubber and tire manufacturing
6. Electric Services – coal-fired power plants
7.  Fabricated Metal – aluminum fabricating operations, metal powder generated after cutting or grinding
8. Equipment Manufacturing – machinery, device equipment
9. Furniture and Fixtures – woodworking facilities, furniture manufacturing
10. Others – coal mining

Additionally, any industry that processes the following in powdered form is at risk: 
• Agricultural products (sugar, candy, spices, feed)
• Agricultural dust (cocoa powder, garlic powder)
• Carbonaceous dust (coal, cork, corn)
• Chemical dust (lactose, dextrin) 
• Metal dust (aluminum, bronze) 
• Plastic dust (epoxy resin, vinyl) 

 
A Coal-Fired Power Plant

Combustible Dust Explosions

Here is another question we often hear: how does a dust explosion occur?  Well, let us tackle that question.  Dust gathers on rafters, roofs, suspended ceilings, and other equipment.  When even a small build-up of combustible dust is disturbed, there is potential for an explosion (or “deflagration,” another term for a combustible dust explosion). 

A typical fire needs three elements, called the fire triad: 

• Fuel - dust particles
• Oxidant - a source of oxygen or oxidizing material
• Ignition source - a spark or open flame

However, a dust explosion needs two additional elements to create the “dust pentagon”: 

• Dispersion - airborne fuel via a dust cloud moved from one place to another; the cloud moves due to a mechanical process (e.g., transport)
• Containment or confinement - a dust cloud develops in an enclosed area; a rapid shift in temperature triggers a rapid change in pressure which triggers an explosion

Without all five points on the pentagon, a dust explosion can’t happen.

When combustible dust ignites, there are frequently two explosions that occur: a primary and secondary explosion.  The primary dust explosion is the first explosion, which occurs when there is a dust suspension in a confined space (such as a container, room, or piece of equipment), and with all of the other four pentagon elements present.  The primary explosion then unsettles other dust that has collected.  It’s at this point, when the dust becomes airborne, that it can also ignite.  This is the secondary dust explosion, which is oftentimes more destructive than the primary one.

While we suspended our space exploration for a moment, we did promise to revisit the galactic center.  Can you see the similarities in what’s required for a dust explosion in space or on Earth: heat, dust, clouds, gas, flames, and a confined area?  We are clearly not astrophysicists, so we will stop the comparison there, as we don’t want to oversimplify the creation of stars.  Our goal is mainly to stress that when these forces come together, nature clearly shows us that powerful things emerge as a result.

 
Some other possible ignition sources for combustible dust include vehicles, processing equipment, and cleaning activities.
Industrial Safety & Hygiene News (ISHN) shows the following as potential ignition sources:

• Electrical shorts
• Electrostatic discharge
• Flames
• Hot work
• Hot surfaces
• Rotating equipment
• Sparks

Food Processing Equipment

NFPA Combustible Dust - 652 and 654 

NFP 652 provides industries with an established, unified, baseline combustible dust standard.  It explicitly sets rules and defines fire, flash fire, and explosion hazards.  NFPA 652 emphasizes identifying and managing hazards of combustible dusts and particulate solids, whereas NFPA 654 focuses on fire and dust explosions from the manufacturing, processing, and handling of combustible particulate solids.

NFPA 652 also tasks the owner of the facility with assigning a qualified person or team to conduct dust inspections and provides further guidelines on how to perform a dust hazard analysis.  You can also take a look at the best standards and practices to prevent dust explosions in NFPA 654. 

September 7, 2020, is the compliance deadline for the new NFPA 652, or the mandatory Dust Hazard Analysis, required at any facility where combustible particulate solids are contained.  Even though the period does not start until late 2020, NFPA 652 expects that each facility makes reasonable progress toward meeting the standard each year.  This rule was established in 2015, so if you haven’t started yet, you’re out of compliance. 

Other NFPA dust codes worth noting:
NFPA 484 – standard for combustible metals
NFPA 61 –  standard for the prevention of fires and dust explosions in facilities handling, processing, or storing bulk agricultural products 
NFPA 655 – standard for the prevention of sulfur fires and explosions
NFPA 664 – standard for wood processing and woodworking processing facilities
NFPA 68 – standard on deflagration venting
NFPA 69 – standard on explosion prevention systems

Identifying Potential Dust Explosions  

 
There’s an urban legend that dust accumulation must be thick enough to write in or as thick as a paperclip for an explosion to occur -- this isn’t a reliable metric, and it’s a much better practice to keep the workplace as free of dust as possible to keep workers and the jobsite safe. 

To prevent a dust explosion, OSHA suggests a regular and exhaustive hazard assessment of: 

• Any materials handled and the location at which they were handled 
• All operations and their by-products
• Every space within the workplace, both open and hidden
• All potential ignition sources

Within the new NFPA 652:2016 Standard on the Fundamentals of Combustible Dust, a dust hazard analysis is required.   

Ignition Control - Prevention Is Better Than Cure 

We provide users with high-quality PPE; however, we recognize upfront workplace controls are better than personal protective equipment, as those controls can stop the hazard in its place.  Our goal is only that you’re safe and protected from workplace hazards.

To prevent a dust explosion, it’s essential to maintain proper control of your ignition sources.  You can do this by following a few easy safety tips. 
Use safe and proper electrical equipment and wiring -- always dispose of frayed wires immediately, and don’t leave wires running in walkways. 

1. Control static electricity by bonding equipment to the ground. 
2. Prevent smoking, sparks, and open flames. 
3. Keep heating systems and surfaces away from dust and dust sources. 

Also, a housekeeping and dust control program should be established to keep dust deposits under control.  In addition to presence of ignition sources, the accumulation of dust in work areas is a contributing factor to combustible dust explosions.  Just remember the three C’s: Capture dust before it escapes, Contain the dust, and Clean work areas, overhead surfaces, and concealed spaces.

Cleaning methods that don’t generate dust should always be used (i.e., avoid brooms and compressed air hoses that push the dust around), and remember to search overhead structures for hidden accumulations of dust.  

OSHA Combustible Dust and FR Clothing   

 
OSHA has been attempting to install a formal mandate around combustible dust since 2008, when a dust explosion in Port Wentworth, Georgia, killed 14 people and injured 38 more.  In March 2017, however, OSHA withdrew its rulemaking proposal to create a general industry standard around combustible dust.  So, yes, currently, there is not an official OSHA combustible dust standard in place; however, OSHA has adopted the new NFPA 652 standard.  

The most common dust explosion injuries occur after the flash fire when fabric that isn’t flame-resistant (FR) has caught fire and burnt or melted to the victim’s skin.  However, FR gear refuses to ignite unless directly in contact with the source of ignition and it self-extinguishes when the heat source is removed to avoid burns. 

Many organizations are getting ahead of the curve and adding flame-resistant gear to their PPE arsenals early since it’s cheaper than a hospital bill and FR PPE is incredibly useful as a preventative measure.  Just take a look at some of the workplace stats we identify on our flame-resistant clothing page.  

Helpful OSHA Information
 Combustible Dust Hazard Guidance
 Combustible Dust in Industry
 Combustible Dust Quick Cards
 Hazard Alert: Combustible Dust Explosions
 Hazard Awareness
 Risks Associated with Combustible Dust Hazards

MCR Safety FR Clothing – Triple-Vented

What’s unique about this technology?  Its mesh triple venting is incorporated onto the back and under the arms, allowing body heat to escape where it builds up the most.  ts triple venting provides exceptional comfort levels.  Plus, this technology offers 47% greater flash fire performance, which is something you’re going to want to check out if you deal with the potential for combustible dust flash-fires.  When explosive energy like this occurs, our goal is to minimize burn injuries and have a wearer emerge in star-like condition!

Summit Breeze® Technology

Since fire-resistant (FR) clothing must be worn in areas where combustible dust is present, it often means working where heat exists.  Summit Breeze® technology provides better heat stress management for those working in a hot environment, those who are performing labor-intensive tasks, or a combination of the two.  When working in an environment prone to heat stress, vented openings can be a lifesaver.   

MCR Safety is the only manufacturer providing FR clothing with three total FR mesh vent openings, allowing for exceptional airflow.  As we’ve highlighted above, if you’re looking to supply your employees with it and it’s not being offered in your FR rental program, give us a call.

When the dust settles, workers wear FR Clothing power by Summit Breeze Technology!

MCR Safety’s FR Clothing Resources

MCR Safety believes in offering high-quality products that provide superior protection.  In addition to that, we are passionate about making sure you’re informed when making crucial PPE decisions.  Here are links to numerous resources to stay up-to-date on all relevant PPE, standards, hazards, and much more. 

Here are the resources we’ve assembled to help you find the most appropriate FR clothing:
o FRC Resource Page
o FRC Knowledge Center
o FRC Electric ARC Performance 
o FRC 70E 
o FR Online Catalog
o Summit Breeze® Page 
o Summit Breeze® PDF

 
Summit Breeze® PDF on the left side; FR Online Catalog on the right side.

Before We Wrap Up

We’ve covered a lot of material above, but we want to make sure we highlight the most common questions we receive:

• Did OSHA change the combustible dust standard?  We have an entire section regarding this question above.  While OSHA dropped its rulemaking process in 2017, it has since adopted NFPA’s combustible dust standard, affecting numerous industries and workers.  You will likely be fined if NFPA standards are not met.  Here is a recent OSHA citation highlighting NFPA 652.  

• Is flour dust combustible?  Oat flour, potato flour, rice flour, rye flour, wheat flour, and wood flour are all shown in OSHA’s combustible dust list.
• How does combustible dust ignite?  This question is covered in-depth above.  Five factors must be present: dust, a confined area, dispersion of the fuel, oxygen, and an ignition source.

• Is baking soda combustible?  Sodium Bicarbonate, also known as baking soda, is non-combustible and is used in fire extinguishers.
• Is it possible to monitor for combustible dust?  Yes, it only requires conducting measurements and an active commitment to preventing the hazard.  For more information, check out ISHN’s article on Detecting Dangerous Combustible Dust.

• Is all dust combustible?  There are materials that are non-combustible, however, due to other materials potentially mixed with that material, any activity that creates dust should be investigated by conducting a hazard analysis. OSHA's Hazards Related to Combustible Dust provides some excellent information to assist companies.

• Is wood pulp a combustible dust?  Yes, fewer explosions occur in Pulp and Paper than in other industries, however, combustible dust hazards still present a threat to workers.

Combustible Dust Safety

Until recently, companies may have looked the other way when it came to combustible dust hazards.  Employee injuries and the potential loss of human life likely with a combustible dust explosion should always be enough concern in and of themselves for most companies to take action.  With the new NFPA 652 standard in place, there is no choice but to keep workers safe by taking better safety measures and providing superior FR clothing.  If you need assistance with identifying hazards or arming your team with advanced flash fire FR clothing, a local MCR Safety representative can be in touch and provide a detailed 360° analysis of your facility’s operation.

For over 45 years, MCR Safety has proven to be a world leader in gloves, glasses, and garments.  Whether it’s on the shop floor, an oil rig, or a construction site, we are there providing solutions to workplace hazards.  It’s all part of our commitment to protect people. 

No matter your industry, we have the personal protective equipment you need.
We Protect People!

Learn more about MCR Safety by checking out our most recent video.  For more information, browse our website, request a catalog, find a distributor, or give us a call at 800-955-6887.