Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure.  Coal is composed primarily of carbon along with variable quantities of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.

Coal dust is a fine powdered form of coal, which is created by the crushing, grinding, or pulverizing of coal. Because of the brittle nature of coal, coal dust can be created during mining, transportation, or by mechanically handling coal.

Coal dust particulates are of particular concern because they contain heavy metals which are toxic at low concentrations. They include lead, mercury, nickel, tin, cadmium, mercury, antimony, and arsenic, as well as radio isotopes of thorium and strontium.

Coal dust, especially fine coal dust, has been identified by health professionals and doctors around the world as causing a range of diseases and health problems.  Examples include an increased incidence of heart and respiratory diseases like asthma and lung cancer.

The health risks increase with the level and frequency of exposure.

As fine coal dust accumulates in the lungs over time duration of exposure is also a risk factor. 

Coal Dust is Combustible and is an Explosion Hazard:

When most people think of controlling dust in the workplace, they think of taking steps to avoid inhaling dusts to prevent health problems. However, the accumulation of combustible dusts in the workplace can lead to far greater consequences. As seen in recent years, neglect of housekeeping and improper handling of combustible dusts can lead to property damage, injuries and loss of life.

Coal dust suspended in air is explosive.  Coal dust has far more surface area per unit weight than lumps of coal, and is more susceptible to spontaneous combustion.

As a result, a nearly empty coal store is a greater explosion risk than a full one. The worst mining accidents in history have been caused by coal dust explosions. Explosions were usually initiated by firedamp ignitions, the shock wave of which raised coal dust from the floor of the mine galleries to make an explosive mixture.  

The National Fire Protection Association (NFPA) defines a combustible dust as “a combustible particulate solid that presents a fire or deflagration hazard when suspended in air or some other oxidizing medium over a range of concentrations, regardless of particle size or shape.” In general, combustible particulates having an effective diameter of 420 μm or smaller, as determined by passing through a U.S. No. 40 Standard Sieve, are generally considered to be combustible dusts. However, agglomerates of combustible materials that have lengths that are large compared to their diameter (and will not usually pass through a 420 μm sieve) can still pose a deflagration hazard. Therefore, any particle that has a surface area to volume ratio greater than that of a 420 μm diameter sphere should also be considered a combustible dust. The vast majority of natural and synthetic organic materials, as well as some metals, can form combustible dust. The NFPA’s Industrial Fire Hazards Handbook states, “any industrial process that reduces a combustible material and some normally non-combustible materials to a finely divided state presents a potential for a serious fire or explosion.”

Suggested Industrial Vacuums for Recovery of Toxic & Combustible Dust

PrestiVac HEPAPlus* Vacuums are specifically designed to safely vacuum toxic dusts. Equipped with a Certified Absolute HEPAPlus*filter with an efficiency of 99.995% on 0.2 micron so there is no risk of exposure or contamination for the operator or the environment. These vacuums are tested for absolute filtration. Testing Method: IEST RP-CC034.3. H14. MIL-STD 282 / A.S.T.M. - D2986-91.  MPPS method EN 1822.

PrestiVac Explosion Proof/Dust Ignition Protected Vacuums are designed to safely vacuum explosive, flammable, combustible conductive* dusts. Our Explosion Proof/Dust Ignition Protected Vacuums are completely grounded and static dissipating because they are built entirely with non-sparking metals and do not have any painted components so there is no risk of fire or explosion from a spark or static build up. All the electrical components, including the motor and starter are totally enclosed so there is no source of ignition. Our explosion proof vacuum cleaners comply with NFPA 484 guidelines and are an effective tool for good housekeeping practise as per OSHA.

Which Industries are at Risk with Coal Dust?