Employers and safety managers have long looked to flame-resistant (FR) and arc-rated (AR) garments to help protect workers from injury due to flash fire and arc flash. Because these garments are designed using specially engineered, self-extinguishing fabrics and are certified to rigorous testing standards, they can help prevent or lessen the severity of injury.
Utilizing FR/AR garments as part of a comprehensive PPE (personal protective equipment) program is one of the ways employers can meet their obligation to “provide workers with employment and a place of employment that are free from recognized hazards.”1
Questions arise, however, when outside temperatures rise - or plummet. Is it possible to maximize protection while at the same time minimizing the risk of heat stress and cold stress? The answer is yes, but finding the right solution requires an understanding of several interrelated factors, one of them being how our choosing FR/AR garments to keep workers cool.
1. Before thinking about the cooling potential of clothing, it’s imperative that you choose FR/AR garments rated to the hazard. Protection is your primary consideration. Look to ASTM F1506 and F1891 for arc flash and NFPA® 2112 and ASTM F2733 for flash fire requirements, but keep in mind that these are the minimum requirements and ratings for the hazard. It’s also important to note that single-layer FR/AR clothing is no hotter than non-FR clothing and it provides the protection your workers need.
2. Next, choose fabrics that assist with cooling:
a. Open-weave fabrics allow more air to contact the skin (convection).
b. Lighter weight fabrics, if they have an open weave, are less insulating, so they allow for greater release of excess heat (radiation). Note that “light weight” as a single attribute does not necessarily equate to comfort.
c. Moisture-wicking garments move moisture away from the skin to the surface of the fabric (evaporation). Always make sure that moisture wicking is due to a garment’s fiber combination and not a finish that will lose effectiveness over time.
3. Finally, monitor workers carefully when utilizing additional PPE layers that may prevent body heat from escaping or sweat from evaporating, such as:
a. Arc flash suits
b. Rain gear
c. Hi Vis vests
d. Chem protection
e. Soil protection (disposable overalls)
A word on FR/AR base layers
Moisture-wicking FR/AR base layers not only provide additional protection against thermal energy, but also allow for greater moisture management by moving sweat away from the skin and into the mid and outer clothing layers.
While industry standards for both arc flash and flash fire do allow for all-natural, non-meltable base layers, if these garments are flammable, the arc rating of the outermost FR/AR layer must be sufficient to prevent break open. If the outer layer is not equal to or greater than the hazard, then all base layers must also be arc rated.
In addition to understanding how various fabrics and fibers can keep workers cool, building the right combination for your workers requires an understanding of:
With these tools in hand, workers should be able to manage their body temperatures throughout the day and take action as needed to maintain their health and safety.
1 Occupational Safety and Health Act, Section 5(a)(1), 1970.