Several Questions and Answers about NFPA 70E
- Categories:Industry news
- Time of issue:2015-08-21
Several Questions and Answers about NFPA 70E
1.What is NFPA 70E and why is compliance with this standard so important?
The National Fire Protection Association 70E Standard is a comprehensive standard that contains detailed instructions on how to protect workers from the heat of electric arc exposures.
2. Who is covered under NFPA 70E?
Employees during activities such as operation, maintenance and demolition of exposed energized electrical conductors or circuit parts. Research shows that approximately 10% of the employees in any operation work as electricians, maintenance, or other categories of work covered by this standard.
3.What job tasks are not covered under NFPA 70E?
Examples of job tasks not covered under the 2000 Edition of NFPA 70E include installations that occur:
In ships, watercraft, railway rolling stock, aircraft, or automotive vehicles other than mobile homes and RVs
In underground mines
On railways used exclusively for the operation of rolling stock
On communication equipment under exclusive control of communication utilities
Under the exclusive control of electric utilities for generation, transmission and distribution
4.Are electric utilities covered under NFPA 70E?
No. Currently, NFPA 70E guidelines do not cover the generation, transmission and distribution areas of electrical utilities.
5. Does OSHA enforce NFPA 70E?
OSHA believes that the NFPA 70E standard offers useful guidance for employers and employees attempting to control electrical hazards, but OSHA has not conducted a rulemaking and therefore does not "enforce" NFPA 70E. OSHA does use consensus standards, such as NFPA 70 as evidence of hazard recognition in evaluating General Duty Clause violations.
6. What is ATPV EBT?
The standard requires that arc rated garments have a minimum Arc Thermal Performance Value (ATPV) based on the hazard/risk analysis for the task being performed. The ATPV is expressed in calories per square centimeter and represents the protection from electric arcs provided by the garment. If the ATPV cannot be calculated because the fabric breaks open, the energy causing the break open in expressed as the Breakopen Threshold Energy (EBT).
7. Where do I find arc ratings?
Arc ratings are included on Drotex® flame resistant garment labels and in Drotex® flame resistant apparel brochures.
8. Is there apparel that offers a higher level of protection than is available from single layer garments?
Electrical switching clothing (flash suits) is available for those needing HRC 3 (25 minimum ATPV) or HRC 4 (40 minimum ATPV). Many insulated outerwear garments also have ATPVs greater than 25. These can be used for specific applications where higher arc ratings are needed. Keep in mind that hearing, head, face and neck protection are also required for these higher exposure levels.
9. How do I do calculations in NFPA 70E?
Arc rated clothing and personal protective equipment (PPE) must be worn either based on the calculated incident energy determined for the specific task or by using Table 130(C)(9) to determine the hazard/risk category (HRC).
HRC is specified based on specific job tasks.
These range from HRC 0 that allows non-melting flammable materials up to HRC 4 that requires an arc rated flame resistant shirt and pants or flame resistant coverall, and arc flash suit with a minimum system arc rating of 40.
Annex H provides a simplified approach to selecting appropriate arc rated clothing and PPE based on whether the ask requires "everyday work clothing" or "electrical switching clothing."
10. Can those covered by this standard just wear heavyweight non-melting flammable garments such as denim jeans?
Probably not. Non-melting flammable garments are only allowed for HRC 0 exposures. Employees must wear flame resistant apparel wherever there is a possible exposure to an electric arc flash above the threshold incident-energy level for a second-degree burn (1.2 cal/cm2).
11. Can workers continue to wear flammable T-shirts under their arc rated garments?
Layers of non-melting flammable garments are permissible to be worn under flame resistant apparel for added protection.
However, if Table 120.7(C)(9) is used to determine the HRC, only flame resistant layers within the layered system are used to determine system arc rating.
Arc Ratings of individual layers cannot simply be added together. Any garment worn as the outer layer, including rainwear, must be flame resistant.
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