Flame Resistant Clothing
The “269” Standard (1910.269)
Prohibits workers from wearing clothing that, in the presence of an arc, can potentially increase the extent of injury; that is, if the clothing would ignite and continue to burn, or if it melts on the skin. Thus, workers are generally prohibited from wearing clothing materials made entirely of, or blended with, synthetic materials such as acetate, nylon, polyester, or rayon.
FR Clothing and the “269” Standard. OSHA issued an interpretation memorandum that provides guidance for complying with the apparel requirements. This memorandum provides information on acceptable types of clothing and on the employer’s assessment of the hazards.
PPE Flame Resistant Clothing
Arc flash and flame-resistant clothing protects workers from burn injuries in areas with sparks, open flame, and other potential fire hazards. Also called FR clothing, this protective clothing resists ignition and helps insulate against heat. Flame-resistant garments are made of materials that naturally resist burning or melting. Flame-retardant garments that are chemically treated to self-extinguish. Arc flash protection garments are a specialized flame-resistant clothing worn when working near electrical equipment where arc flash hazards exist. Aluminized clothing reflects radiant heat to help maintain a safe body temperature.
For example, working with low-voltage wiring with minimal likelihood of an arc flash occurring would not require extensive PPE. On the other hand, working on a high-voltage machine involves a very serious risk of an arc flash, so a category 4 rated PPE is likely going to be needed in this case.
Each category includes the minimum Arc Rating value for the required PPE, which represents the amount of incident energy (in cal/cm^2, or calories of heat energy per square centimeter) on a fabric or material that carries a 50% probability of causing a second degree skin burn injury.
In other words, you have a 50% chance of being burned if exposed to an electric arc with the same number of calories of heat. The arc rating indicates the level of protection provided by Flame Resistant (FR) clothing measured in cal/cm^2. The higher the value the greater the protection.
Arc flash PPE is required by NFPA 70E (2018) as per 130.7: