What was happened at the Imperial Sugar refinery northwest of Savannah, Georgia, on February 7, 2008, illustrates how dangerous combustible dust is if it is not treated properly.
In that accident, 14 people died and 38 others injured, including 14 people with serious and life-threatening burns.
In this post, you are going to learn some important facts about combustible dust that you must take care of.
The purpose of this post is after reading this post, you will be able to take necessary actions to prevent similar explosion accidents from happening.
Combustible Dust Definition
We will start with the definition.
What is combustible dust actually?
There are several definitions we can find about that term, and here are some of them:
OSHA (Occupational Safety and Health Administration): combustible dust are fine particles that present an explosion hazard when suspended in air under certain conditions
CCOHS (Canadian Center for Occupational Health and Safety): combustible dust is any fine material that has the ability to catch fire and explode when mixed with air.
NFPA (National Fire Protection Agency): it is defined as dust particles that are 500 microns or smaller and present a fire or explosion hazard when dispersed and ignited in air.
WHMIS (Workplace Hazardous Materials Information System): it is defined as a mixture or substance that is in the form of finely divided solid particles that, upon ignition, is liable to catch fire or explode when dispersed in air
How Do Combustible Dust Explosions Occur?
Combustible dust explosions can occur if there are five (5) elements exist. If one of those five elements is unavailable, it will not occur.
Three elements (3) are called the fire triangle. Meanwhile, those five elements are called the dust pentagon.
- Fuel to burn
- Ignition source
- Combustible dust dispersion in the air in a certain concentration
- Confinement of the combustible dust cloud
If you could control these elements, combustible dust explosions will not happen.
What are Examples of Combustible Dust?
Unfortunately, most people may not aware of the existence of combustible dust in their workplace. This situation is very dangerous since this can cause a severe accident.
Ideally, an effective hazard identification process can identify the existence of combustible dust along with its sources. But, in most cases, this does not happen.
If this is the case, then a combustible dust list will be definitely helpful.
In fact, OSHA has published a list of combustible dust that you can use as a reference.
Here they are:
Milk, nonfat, dry
Cocoa bean dust
Coconut shell dust
Lemon peel dust
Locust bean gum
Oat grain dust
Peanut meal and skins
Raw yucca seed dust
Sunflower seed dust
Wheat grain dust
(wood flour and
(poly) Methyl acrylate
(poly) Methyl acrylate,
(poly) Vinyl acetate/
(poly) Vinyl alcohol
(poly) Vinyl butyral
(poly) Vinyl chloride/
(poly) Vinyl chloride/
After knowing the list, what you should do is to identify the existence of these above lists, through the hazard identification process.
Combustible dust cleaning is an important aspect to prevent accumulation. This work should be done regularly on all work areas, including high surface areas such as ceiling, ducting, piping, and top of machinery.
Having a regular cleaning schedule is very important.
If you cannot do the cleaning work by yourself, you can ask a dust cleaning service company to do it for you. Such a company has well-trained workers and good procedures for doing that job.
Ignition Sources Control
Besides dust cleaning, ignition sources control is another important action that you have to do to prevent combustible dust explosions.
HSE.gov.uk has listed up ignition sources, that may come from:
- Direct fired space and process heating;
- Use of cigarettes/matches etc;
- Cutting and welding flames;
- Hot surfaces;
- Heated process vessels such as dryers and furnaces;
- Hot process vessels;
- Space heating equipment;
- Mechanical machinery;
- Electrical equipment and lights
- Spontaneous heating;
- Friction heating or sparks;
- Impact sparks;
- Sparks from electrical equipment;
- Stray currents from electrical equipment
- Electrostatic discharge sparks:
- Lightning strikes.
- Electromagnetic radiation of different wavelengths
- Vehicles, unless specially designed or modified are likely to contain a range of potential ignition sources
To control the above ignition sources, HSE.gov.uk, has outlined the following countermeasures:
- Select appropriate equipment for certain zone (hazardous area classification).
- Use proper grounding or earthing for all the plant equipment
- Avoid any surfaces above auto-ignition temperatures of flammable materials being handled
- Provide lightning protection
- Prohibit smoking and the use of matches or lighters
- Avoid and control spark generation and static electricity
- Replace damaged power cable immediately
- Controls over activities that create intermittent hazardous areas, e.g. tanker loading/unloading