Combustible Dust Explosions: Is Your Workforce at Risk?

Dust explosions continue to be a persistent problem for many industries resulting in loss of life, injuries and destruction of property. 

• By Tim Turney
• Sep 01, 2021

Combustible dust-fueled fires and explosions continue to injure and claim workers' lives across a broad spectrum of industries. Agriculture, food production and wood processing make up the largest proportion of the overall fire and explosion incidents. However, any workforce that generates dust may be at risk, with incidents occurring in businesses as diverse as pulp and paper, textiles and pharmaceuticals.

Tragedies such as the Imperial Sugar refinery explosion in Georgia, responsible for 14 deaths and deemed by the U.S. Chemical Safety Board as the most devasting dust explosion in decades, offer a grave reminder that businesses need to monitor dust levels efficiently. It is also now well understood that short and long-term exposure to dust poses significant health risks. Effects range from increased hospital admissions to a higher risk of premature death, primarily due to cardiovascular and respiratory disorders.

While the cost to worker health is incalculable, employers run the risk of reduced productivity, rising costs due to sickness days, increased costs for training and recruitment and catastrophic penalties and compensation claims. For example, OSHA proposed penalties of $215,525 for an explosion believed to be caused by dust ignition sources at MFA Enterprises Inc. last December, leaving the company’s employee severely injured.

Understanding How Dust is Created

Dust is created when materials are transported, handled, processed, polished, ground and shaped. Dust can also form from abrasive blasting, cutting, crushing, mixing, sifting or screening dry materials. In addition, the build-up of dried residue from the processing of wet materials can generate dust. Dust in the workplace rises daily from these activities, which is why employers need to stay vigilant to exposure levels to protect workers from hazardous incidents and the potential of life-threatening consequences.

How Employers Can Cut the Risk of a Combustible Dust Explosion

Explosive and combustible dust is covered under OSHA's General Duty Clause. To prove that a company has violated the clause, the federal agency must show that the business knew of a hazard in their workplace and did nothing to prevent or stop it.

These conditions apply if:

*The employer did not keep the business free of the hazard and exposed workers to it

*The hazard is recognizable

*The hazard is likely to cause severe injury or death

*Feasible methods existed with which to correct the hazard, but the employer did not utilize them In accordance with the clause, it is the employer’s responsibility to protect employees from explosive and combustible dust risks in the workplace. Therefore, employers need to identify where explosive atmosphere conditions occur, assess the risk and record what actions are being taken to prevent an explosion and fire. A combustible dust explosion can only occur when the following five factors are present:

*Fuel, in the form of dust particles

*Dispersion of the fuel in the form of a dust cloud

*Oxygen in the form of air

*Confinement of the dust cloud in the form of a container (e.g. a dust collector)

*A source of ignition

There are several ways dispersion can occur, such as a dry filter being pulse cleaned or from an initial explosion in processing equipment, causing a blast wave that disturbs accumulated dust that, if ignited, causes a secondary explosion. The latter is often far more destructive than a primary explosion due to the increased quantity of dispersed dust.

Monitoring Dust Concentration to Mitigate Risks

Undertaking a walk-through survey using a hand-held, real-time sampler can provide an instant indication of dust concentration. It can also be used to check the effectiveness of control measures, for example, a local exhaust ventilation pre and post filter.

Industrial hygienists may already be undertaking personal monitoring for toxic or sensitizing dusts. If so, the same air-sampling pump can be used in combination with a real-time sampler when housed in a robust, portable case, on an unattended, short-term basis. Such a system can provide concentration using a gravimetric filter but also a time history profile, which could help identify the source of the problem.

Fixed, AC powered solutions can also be used on a continuous basis for high-risk areas. These have the advantage that the data can be made available remotely using a web-based interface. These systems provide real-time alerts via text message or email should limits be exceeded. Reports can be automated and sent to multiple users, allowing for early intervention to avoid potential problems. However, great care should be taken in hazardous atmospheres that may require instrumentation to be intrinsically safe or require a hot-work permit. Action thresholds should always be set at a fraction of the Lower Explosion Limit (LEL) for the dust in question. If there is any doubt whatsoever, employers should seek advice from the relevant site manager or supervisor responsible for the risk assessment.

Personal Protection at Work

A personal air sampling pump is a bodily worn pump used to sample for airborne contaminants that can be damaging to health. With the ability to provide real-time data about dust levels, identifying harmful areas of exposure, personal air sampling is an effective method to mitigate risks. Before implementing any monitoring solution, a risk assessment should be conducted to answer some key questions: Who is exposed and to what? How long are they exposed for? How much are they exposed to?

Personal monitoring with an air sampling pump must be practical and operate in a way that it does not disrupt the comfort or productivity of a worker. Pumps can operate at a variety of different flow-rates and are designed to be clipped to the wearer’s belt. A slim, ergonomic design is the ideal solution, as it is non-obtrusive to the wearer allowing him/her to carry on with their job whilst being monitored. Personal sampling instruments highlight exactly when and where excessive dust levels are occurring to support decision-making. Personal monitoring results equip employers and employees alike with greater knowledge that can contribute to a positive workplace health program. Consequently, personal monitoring enables a better understanding of how to protect workers from exposure through changing health and safety procedures and supplying appropriate respirable protection during dangerous tasks. For harmful substance, crystalline silica for instance, personal monitoring is essential, and employers must employ personal dust sampling pumps in order to assess and control exposure effectively. Integrating monitoring pumps should become an established part of the health and safety process for companies. As a result, companies save valuable time while protecting employees, which enhances business efficiency.

Why Employers Need to Understand the Hazards

Dust explosions continue to be a persistent problem for many industries resulting in loss of life, injuries and destruction of property. Even highly trained individuals including government enforcement officials, insurance underwriters and company safety professionals often lack awareness of combustible dust hazards. Material Safety Data Sheets (MSDS) are also ineffective in communicating to employers and workers the hazards of combustible dust explosions and ways to prevent them. This is all the more reason for all employees to have a basic awareness of the hazards of dust explosions and the best way to mitigate those risks.

This article originally appeared in the September 2021 issue of Occupational Health & Safety.