Page 40 - OHS, May 2020

COMBUSTIBLE DUST
The Role of FR Garments in Mitigating Combustible Dust Hazards
FR garments also play a vital role in effective combustible dust hazard prevention.
BY SCOTT FRANCIS
As a hallmark of arc flash or flash fire miti- gation programs, flame resistant (FR), arc-rated (AR) garments help protect em- ployees against short-term thermal work- site hazards. These garments work together with other preventative safety measures to ensure indus- trial workers across various industries can remain safe while performing their job. What many do not realize is that FR garments also play a vital role in effective combustible dust hazard prevention and mitigation.
Simply put, combustible dusts are fine particles that can trigger serious incidents like explosions, def- lagrations and flash fires. When paired with oxygen and heat, properly dispersed amounts of this type of dust acts as a fuel that rapidly combusts and causes a pressurized fire known as deflagration. Deflagrations in equipment or contained processes can lead to com- bustible dust explosions, which result when a defla- gration encounters one additional pressure building element: containment. Since explosions can further disperse combustible dust throughout a facility, a chain reaction of secondary deflagrations can occur. Furthermore, a combustible dust incident can also cause flash fires, which may lead to second- or third- degree burns—even if a person is not in the direct vi- cinity of the original explosion.
Because combustible dusts are often made of or- ganic or metal particles—plastic, food, textile, paper and metal dusts, for example—this hazard poses a threat across multiple industries. When equipment or process conditions enable dispersed combustible dust to act as fuel, there is a strong risk of a flammable or explosive incident should all four deflagration condi- tions or five explosion conditions present themselves. What is more, there is no uniting threshold level of dust accumulation needed to trigger an incident. Only a detailed risk assessment can identify a work- site’s specific hazards.
Using NFPA 652: Standard on the Fundamentals of Combustible Dust as the guiding consensus stan- dard, safety managers must assess the dust hazards present within a worksite and determine if the dust is combustible, explosive or both. A DHA-Dust Haz- ard Analysis—which now must be completed by a qualified person per NFPA 652 before September 7, 2020—utilizes the hierarchy of risk controls to com- plete a thorough risk assessment. This assessment can help pinpoint a proactive plan that reduces the likelihood of a site combustible dust event through dust elimination; engineering controls, like venting or suppression; and administrative controls, like
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housekeeping. One final control—the use of per- sonal protective equipment (PPE)—turns the focus from proactive and preventative measures to defen- sive, mitigative measures.
If the immediate and most recognizable threat facing those working around combustible dusts is an explosion, why then is PPE, and in particular FR gar- ments, so important?
It is well-known that FR garments are not shields and cannot protect a worker within a blast radius. They can, however, serve as critical safety linchpins, helping close the risk gap and mitigate the potential for injury or loss of life. FR garments can also help extend escape time so that employees can quickly and safely retreat from an incident.
With this in mind, we explore three proof points that make a strong case for incorporating FR gar- ments into combustible dust safety programs.
Fire is Present in a
Combustible Dust Incident
Whether through deflagration or flash fires, industrial workers face serious burn risks should a dust incident occur. It could be a single deflagration, or a chain of flash fires, but a combustible dust incident ignites these dust particles and creates an unstable situation where fire can easily spread throughout a worksite.
Why FR garments? Non-FR clothes ignite and continue to burn long after a flame source is removed, acting as the fuel that ignites and continues to burn long after the thermal source is removed. FR garments combat this issue through its functionality—these garments self-extinguish once a flame source is re- moved and provide sufficient insulation from second- and third-degree burns. While FR garments cannot prevent burns entirely, it can help drastically reduce the severity of burn injuries and significantly increase the probability of survival.
Burn Injuries are Serious Injuries
Pulling data from the U.S. Chemical Safety Board, there were 281 combustible dust incidents between 1980 and 2005, which resulted in 119 fatalities and 718 injuries. A 7:1 ratio over fatalities, burns accounted for many of combustible dust-related injuries. These in- juries—often catastrophic in nature—can have long- term repercussions, and some fatalities have under- laying causes in burn injuries.
Why FR garments? Through their insulation properties, FR garments can help alleviate overall burn injuries and lessen life-threatening scenarios. In