by Nick Gromicko, CMI®
Dust is a general name for solid, airborne particles. While most types of dust are relatively harmless, they can sometimes cause sickness or even fuel a fire.
Large dust particles are typically swallowed or coughed up before they reach the lungs, but they can irritate the nose and the tubes that lead to the lungs, potentially causing rhinitis or bronchitis. Smaller dust particles, known as respirable dust, are far more dangerous, as they can bypass the body’s filters and collect in the lungs. There, large immune-system cells known as macrophages swallow dust particles and carry them elsewhere, but not all dust can be removed. Some types of fine dust, such as silica and asbestos, cause permanent scarring in the lungs known as fibrosis. Animal, grain and wood dusts can trigger allergic reactions and asthma attacks.
A few of the more common sources of dust, mostly encountered in commercial settings, include:
- wood dust. Exposure to wood dust increases the risk of developing asthma or bronchitis, or irritation to the nose, sinus, throat and lungs, and a rare type of nasal cancer. Finer wood dusts, such as those from the hardwoods beech and oak, are more dangerous because they are more easily inhaled. At greater risk are people working indoors in areas without adequate dust removal systems and poor ventilation. High amounts of wood dust may be generated by floor sanding, furniture sanding, wood turning, routing, sawing, sweeping and emptying dust from extraction systems. Mold, too, may be present in freshly cut trees, especially those that are stored outdoors in moist conditions. Mold spores can cause inflammation of the airways during sawing, debarking and transportation.
- Cotton may contain a variety of substances that are harmful if inhaled, such as fungi, bacteria, pesticides and fiber. Workers who handle or process cotton may develop tightness across the chest, experience difficulty breathing, or develop byssinosis, known as the “brown lung” disease. Early breathing difficulties are commonly reversible, but advanced stages of respiratory diseases are often permanent and disabling.
- Other sources include coal (causing breathlessness and scarred lungs, called pneumoconiosis), asbestos (causing mesothelioma and scarred lungs) and silica (causing bronchitis, breathlessness, and lung cancer).
In January 2003, six employees were killed and 38 were injured when an explosion destroyed a North Carolina pharmaceutical plant. A federal report concluded that the explosion was fueled by an accumulation of polyethylene dust above the suspended ceiling.
Any material that will burn in air in a solid form can be explosive when divided into dust. The National Fire Protection Association defines combustible dust as "any finely divided solid material that is 420 microns or smaller in diameter, and presents a fire or explosion hazard when dispersed and ignited in air." Some such explosive dusts include coal, other organic material (such as flour, grain and wood dusts), metal, and sulfur. In addition, physical attributes such as size, shape and moisture content further distinguish explosive potential in two dusts of the same chemical composition. All potential sources of dust ignition, such as slipping belts, static electricity or welding, should be kept away from dusty areas. Electrical equipment in these areas should be "dust ignition-proof rated," as even a spark or a hot surface can cause a dense cloud of dust to explode.
- Change or clean your furnace and air-conditioner filters according to the filter manufacturer’s instructions.
- Ensure that the clothes driers and other vents exhaust directly to the outdoors. Inspect the vent duct for obstructions, kinks and holes, and make sure it is attached securely to the appliance.
- Leave your shoes at the door so you don’t track dirt into the house or offices.
- Provide access to all hidden areas to permit inspection.
- Use cleaning methods that do not generate dust clouds.
- Only use vacuum cleaners approved for dust collection.
- Locate relief valves away from dust hazard areas.
- Inspect for dust residues in open and hidden areas at regular intervals.
- Clean inside walls, ceilings, ledges and other surfaces of workrooms regularly to prevent dust from accumulating.
- Use machines that are enclosed or fitted with effective exhaust ventilation to prevent wood dust accumulation.
- Seal air leaks to help reduce air infiltration that could be a source of dust.
- Utilize surfaces that minimize dust accumulation and allow easy cleaning.
- Minimize the escape of dust from processing equipment and ventilation systems.
In summary, dust can cause sickness and fires, but these risks can be reduced through inspection and removal.