Learning how to layer your FR clothing the right way can be a great way to meet safety standards while also optimizing for comfort and convenience. NFPA 70E requires that employees must wear the level of protection necessary to meet or exceed their arc flash exposure. During any given workday, employees can switch between jobs with different arc flash protection requirements; however, it’s not always convenient for an employee to switch from an NFPA 70E PPE Category 2 uniform to a PPE Category 3 flash suit. Employees may just perform the task with PPE Category 2 level protection and risk the potential of severe injury or death, which is not recommended. This is where layering comes in. Instead of switching to a PPE Category 3 suit, an employee can simply layer an arc rated coverall over a PPE Category 2 uniform to create a higher combined protection level. The arc rating of the layered system will be much higher than the single layer but the actual rating can only be known if the layered system has been arc tested. Many systems have been tested and the added protection of the layered system is typically quite a bit higher than adding the two arc ratings together. There are examples of layering 2 garments with PPE Category 2 ratings (min. 8 cal/cm²) that easily make them into a PPE Category 3 system (min. 25 cal/cm²).
How does layering provide adequate protection?
How can layering flame resistant clothing with varying arc thermal protective values provide higher HRC protection when layered? A combination of the added layer plus the air gap that exists between layers of flame-resistant clothing can help to provide a significant amount of additional protection. When flame-resistant garments are layered, the inter-garment air gap actually adds to the overall flame resistance; thus, increasing the protection ratings of the combined FR garments.
Four tips on how to layer FR clothing
1. The helpful chart above shows the PPE Category levels and the minimum ATPV protection level required to meet the minimum NFPA 70E standards for those job tasks.
2. NFPA 70E allows the use of individual flame-resistant garment layers to be used to reach the total required ATPV. To make this layering technique work, you must wear the right combination of clothing to meet the minimum ATPV for the PPE Category of the task and have test data to confirm the combinations rating. For example, to meet PPE Category 2 (8 cal/cm²) you could potentially do any of the following combinations:
• Shirt and pants with an ATPV of 8 cal/cm²
• Shirt and pants with an ATPV of 4 cal/cm² and a coverall with a 4 cal/cm² or greater ATPV (note: the combination would need to be tested to confirm that it meets the required arc rating).
• Coverall with an ATPV of 8 cal/cm² worn over cotton shirt and pants
3. With all layering combinations, you must also remember to wear appropriate under garments, footwear, gloves, and other personal protection equipment for your head, face, neck, eyes and ears.
4. Additionally, the outermost layer, including outerwear, must always be flame resistant and no synthetic materials should be worn—including undergarments.
Final words of caution
Layering for additive protection does have some downsides. First, there is no magic formula that calculates the true combined protection of two or more layers of flame resistant garments. Testing in accordance to ASTM F1959 must be completed to determine the actual combined benefit of a layering solution. Second, layering only provides additional protection to the areas of the body that are covered by the layers. For example, a sleeveless vest layer over long sleeved flame resistant shirt may provide additional protection for the torso, but it will not provide that same protection for the arms.
Not sure what layering solution is right for you and your team? Contact Workrite today and we’ll help you to find the right flame-resistant clothing for your needs.