There are many hazards when working in factories, but a combustible dust explosion is one of the most dangerous. They have been known to injure and actually kill employees and devastate companies. Understanding combustible dust and what causes combustible dust explosions is the first step toward identifying hazards and protecting companies against these deadly disasters.
What Is Combustible Dust?
Combustible dust may look just like regular dust, and in some cases it is. The dust may not even be normally combustible; however, when combined with the right conditions, the dust can burn or even explode. This dust may be seen floating in the air or settled on surfaces, such as rafters, ducts and equipment. It is most dangerous when it is floating in the air; however, even settled dust causes a potential danger if it is disturbed and dispersed into the air. In order to combat some of this loose dust, it may be helpful to implement some of the tactics associated with 5S. 5S focuses on maintaining an organized and efficiently run workplace. To help elicit this behavior it may be helpful to post floor signs in areas that contain hazardous materials or combustible dust.
Why Is Combustible Dust Dangerous?
Combustible dust is dangerous because it causes dust explosions. A typical fire triangle is comprised of oxygen, ignition (heat, spark, etc.) and fuel. In this case, the dust particles are the fuel. So if there are large amounts of dust particles floating in the air or settled on surfaces, that’s like having gasoline everywhere.
A dust explosion requires two more elements beside the typical fire triangle: the right dispersion and concentration of dust particles and confinement. In other words, there needs to be dust particles suspended in the air in a confined environment. These five factors create the Dust Explosion Pentagon, and all are required to create a dust explosion. Overall, for a dust explosion to occur, most of the following conditions must be met:
- The dust has to be combustible
- It needs to be able to release enough heat to sustain the fire
- The dust must be dispersed in the air or be able to become dispersed in the air if it is disturbed
- It must be large enough to spread the flame
- There must be an ignition source of close proximity to the dust. For instance, an open flame can cause this. Post a No Open Flame sign.
- There has to be enough oxygen in the air
When all these conditions come together, a dust explosion is possible and probable.
When the dust cloud ignites, it burns so fast that it often causes explosions that can damage the building and injure employees. However, the explosion may not stop after one explosion. Initial explosions often causes settled dust to disperse into the air, causing secondary explosions, and according to OSHA,
These can be far more destructive than a primary explosion due to the increased quantity and concentration of dispersed combustible dust.” These secondary explosions have been known to devastate entire buildings and kill employees.
-OSHA – Combustible Dust in Industry: Preventing and Mitigating the Effects of Fire and Explosions
There are many reports of organic dust fire and explosions that have injured or killed employees. In February of 1999, a dust explosion at a foundry in Massachusetts injured 9 and killed three. Another dust explosion in January 2003 at a pharmaceutical plant in North Carolina killed 6 and injured 38 employees. At a Kentucky acoustics insulation manufacturing plant in February 2003, 7 employees were killed and 37 injured in a dust explosion.
All of these were caused by poor hazard assessment, communication and poor handling of combustible dust, so all of them could have been prevented with proper planning, standards, assessment and guidelines.
What Types of Companies Are in Danger of Dust Explosions?
Because nearly any type of dust can become combustible if given the right conditions, any business that creates dust is at risk for a dust explosion. The most common types of dust that can cause an explosion include:
- Agricultural products (egg whites, powdered milk, sugar, etc.)
- Metals (aluminum, magnesium, etc.)
- Chemical dusts (coal, sulphur, etc.)
This is only a fraction of the types of dust that can catch on fire and cause an explosion. It is imperative that any business that creates dust follows the proper steps to protect employees from dust explosions. However, some of the most common types of companies for dust explosions include:
- Grain elevators
- Food Production
- Woodworking facilities
- Recycling facilities
- Metal processing facilities
- Pharmaceutical companies
- Plastic and rubber production companies
The dust is created in many ways, including transportation, processing, polished, shaping, blasting, cutting, sifting and mixing. Even wet materials can dry and form dust.
What Are the Preventative Measures for Dust Explosions?
There are many ways to help prevent dust explosions, but the first step is to assess hazard conditions of the workplace. The following should be identified:
- Material that may create combustible dust
- Equipment and processes that create combustible dust
- Areas where combustible dust gathers, including hidden areas
- Possible hazards for dust to be dispersed into the air
- Ignition sources
Once the hazards have been assessed, the company must create a plan to deal with these hazards on a regular basis to prevent the dust explosion.
- Dust control: Control the dust in the air by inspecting everywhere dust can accumulate, including hidden areas. Use dust collection systems and filters and housekeeping to keep dust from settling on surfaces or dispersing throughout the air. Do not use cleaning methods that cause dust clouds near ignition points, and only use vacuum cleaners that have been approved for dust collection.
- Ignition control: Make sure the possible ignition sites are handled properly by using the right equipment and wiring. Control static electricity, open flames and sparks. Keep heated areas and dusts away from each other, and always use equipment properly, following all safety precautions.
- Injury and damage control: Keep the area properly vented, but ensure the vents are not directed at the work area. Invest in fire suppression systems and explosion protection systems.
Combustible dust is a serious danger to any business that creates dust. Even dust that seems harmless can become combustible and cause explosions if given the right conditions. The first step is to identify potential hazards. Using these hazards, a protection plan can be made to ensure dust is not dispersed in the air, ignition sources are kept safe and employees are protected.
- Fire Safety in the Workplace– creativesafetysupply.com
- Combustible Dust 101– safetyblognews.com
- Do A Combustible Dust Test– creativesafetypublishing.com
- Workplace Safety Hazards – The 5 Hidden Dangers– blog.creativesafetysupply.com
- Hot Work Safety Near Storage Containers– realsafety.org
- Who Uses Process Safety Management?– bridge-to-safety.com
- Workplace Safety & Foot Protection– lean-news.com
- How to Establish 5S in the Workplace– blog.5stoday.com
- Arc Flash Safety Requirements– hiplogic.com