Combustible Dust: What It Is, What Causes It, Why It's Dangerous and How To Protect Against It.
Whether you’re concerned about potential dust hazards or seeking OSHA compliance, learn about the life-threatening dangers of combustible dust and essential protection measures.
What is Combustible Dust?
Combustible dust, often called explosive dust, is any combustible material that can burn rapidly when in a finely divided form and is often a by-product created from manufacturing processes. Given the right conditions such as air suspension and concentration, this dust can cause fire, deflagration and even create a dangerous, high-temperature explosion. Even materials that do not burn in larger pieces (such as aluminum) can be explosible in dust form.
What Causes Combustible Dust?
Combustible dust is generated by a wide variety of manufacturing processes, materials, and industries. Combustible dust is typically generated during crushing, cutting, grinding, milling, polishing, and sawing operations. Facilities that generate dust are all potentially at risk. For example, industries and operations which typically produce combustible dust are:
Oral Solid Dosage Production
DEA Controlled Substance Operations
Metal Processing: Aluminum, Chromium, Iron, Magnesium, Zinc
Pulp and Paper
Rubber and Plastics
Why is Combustible Dust Dangerous?
When aerosolized dust combusts it does so without warning and is lightning-quick. While practically invisible to the human eye, combustible dust particles are a deadly hazard causing fire, deflagration, and even explosion. The force from such an explosion can cause employee deaths, injuries, loss of equipment, and even destruction of entire buildings.
When combustible dust ignites, the result is often a chain of explosions known as primary and secondary explosions. The primary dust explosion is the first explosion. It occurs when there is a dust suspension in a confined space (such as a container, room, or piece of equipment) that is ignited and explodes.
The primary explosion will shake other dust that has accumulated. When this dust becomes airborne, it also ignites. This secondary dust explosion is often more destructive than the primary one.
In addition, without proper mitigation exposure to specific products or materials (such as HAPIs and Potent Compounds) may exceed the occupational exposure limit: thereby resulting in negative health impacts. See our “Top 10 considerations for pharmaceutical dust collection" white paper for more details.
This leads to the question of how to prevent Combustible Dust in the first place.
Proper safety and protection measures must be taken to protect your people and limit the damage from combustible dust ignition, which include performing a combustible dust hazard analysis.
How To Protect Against It
Creating a safe workplace starts with a HIPP Dust Hazard Analysis (DHA) designed to protect your facility against combustible dust hazards.
A correctly performed dust hazard analysis as required by NFPA 652 will not only identify dust hazard-related risk but will serve as the foundation for prevention and control measures. The DHA has to be performed or led by a qualified person, reviewing dust properties (e.g. explosivity), safe operating ranges, existing safeguards, and providing documented results.
The risk characteristics for dust are determined by sampling and testing to determine whether a powder or dust is flammable or explosive when exposed to an ignition source.
Burning Rate to determine the ability of a substance to propagate combustion
Minimum Ignition Energy (MIE) to determine the minimum energy of an electrostatic or mechanical spark capable of igniting dispersed dust under ambient conditions.
Minimum Ignition Temperature (Cloud) to determine the minimum temperature of a hot surface capable of igniting a dust cloud
Minimum Ignition Temperature Layer (MIT Layer) to determine the minimum temperature of a hot surface capable of igniting a powder layer
Limiting Oxygen Concentration (LOC) to determine the highest oxygen concentration at which ignition of dispersed dust at ambient temperature and pressure is not possible.
Minimum Explosible Concentration (MEC) to determine the minimum concentration of dust at which ignition is possible.
Dust Explosion Severity to measures a powder's explosion severity according to specific pressure parameters
Additionally, the DHA provides recommendations to mitigate the identified hazards such as facility change actions and additional safeguards where warranted.
These protection measures may include:
Housekeeping - Program and SOP updates to inspect for dust, safely remove dust on a regular basis, and avoid ignition sources.
Education + Training - Ensuring employee awareness of dust hazards, using Personal protective equipment (PPE), and following safety procedures.
Production Changes - Such as the use of less hazardous material and manufacturing process changes to eliminate or reduce dust created.
Administration - Program to establish key safety plans such as fire safety, ignition control, hot work activities (e.g. welding), and dust storage. In addition to confirming fire and explosion protection and prevention equipment is installed and used according to applicable standards or legislation.
Engineering - Solutions such as dust collection systems designed to eliminate or control combustible dust, grounding conductive equipment to control ignition sources, use of intrinsically safe instrumentation, and installation of proper equipment for explosion isolation, suppression, and venting.
Get free estimates, expert advice, and resources on Combustible Dust protection, safety, and OSHA compliance.
Download OSHA's Hazard Communication Guidance for Combustible Dusts to have an overview of the topic and that can be used as a guide in implementing control measures for a dust explosion.