Arc Flash Protection

 

PROTECTION

from electric arc exposure

 

The intense energy and very short duration of an electric arc flash represents a very unique exposure. Everyday work clothes

made from regular cotton or poly/cotton fabrics, regardless of weight, can be readily ignited at some exposure level and will

continue to burn adding to the extent of injury sustained from the arc alone. NFPA70E now requires employees to wear flame

resistant (FR) protective clothing that meets the requirements of ASTM F1506 wherever there is possible exposure to an

electric arc flash. It requires employers to perform a flash hazard analysis to determine the flash protection boundary distance.

 

The standard is designed to protect employees working inside these flash protection boundaries by requiring protective

clothing for the corresponding Hazard/Risk Category that has an ATPV of at least the value listed in the “Protective Clothing

Characteristics” section of the standard (see below). OSHA has confirmed that garments which meet the requirements of

ASTM F1506 are in compliance with OSHA 29 CFR 1910.269 Electrical Power Generation, Transmission and Distribution,

with regard to garments not contributing to burn severity.

 

 

 

NFPA 70E Requirements

 

The National Fire Protection Association (NFPA) published the latest edition of the NFPA 70E Standard (Standard for

Electrical Safety Requirements for Employee Workplaces) in 2004. The revised version requires employees to wear flame

resistant (FR) protective clothing that meets the requirements of ASTM F1506 wherever there is possible exposure to an

electric arc flash. It requires employers to perform a flash hazard analysis to determine the flash protection boundary

distance. The standard is designed to protect employees working inside these flash protection boundaries by requiring

protective clothing for corresponding Hazard/Risk Category that has an arc thermal performance value (ATPV) of at least

the value listed in the “Protective Clothing Characteristics” section of the standard (see table above). The vast majority of

major companies in the U.S. have some employees who work on or near energized electrical conductors or circuit parts.

In addition, the Department of Energy has required that federal and contractor employees comply with NFPA 70E and the

2002 National Electric Code (NEC) references the NFPA 70E standard. Finally, OSHA considers the NFPA 70E standard

a “recognized industry practice.”

 

When incident energy exceeds 40 cal/cm2 at the working distance, greater emphasis than normal should be

placed on de-energizing before working on or near the exposed electrical conductors or circuit parts.

 

 

NFPA 70E: 3 Ways to Analyze the Arc Flash Hazard

 

A Flash Hazard Analysis will determine the flash protection boundary and the personal protective equipment that people

within the flash protection boundary should use. There are three ways provided within NFPA 70E to perform a Flash Hazard

Analysis to determine the required performance level of protective clothing for the corresponding Hazard Risk Category,

which are highlighted below.

 

1.  DETAILED FLASH HAZARD ANALYSIS

 

There are multiple tools available to the industry to help perform a Flash Hazard Analysis on energized equipment. Where it

has been determined that a person will be working within the flash protection boundary, the Flash Hazard Analysis shall

determine, and the employer shall document, the incident energy exposure of the worker (in calories per square centimeter).

The determination of the incident energy can be performed using multiple tools:

                 NFPA 70E Equations (Examples given in 70E; Annex D)                  • ArcPro (Kinectrics)

                   • IEEE 1584                                                                                    • SKM Power Tools

 

After the incident energy has been determined and documented, the proper fabric for the protective clothing can be selected.

 

2.  NFPA 70E HAZARD/RISK CATEGORY CLASSIFICATIONS OR JOB TASK MATRIX

 

The second way to perform a hazard risk assessment is using the Hazard/Risk Category Classifications of Job Task Matrix

provided in NFPA 70E.  Below are excerpts of the most common job tasks and the corresponding Hazard Risk Category:

 

 

3.  ANNEX H SIMPLIFIED; TWO CATEGORY, FLAME-RESISTANT (FR) CLOTHING APPROACH

 

The use of table H.1 is suggested as a simplified approach to ensure adequate PPE for electrical workers within facilities with

large and diverse electrical systems. The clothing listed fulfills the minimum FR clothing requirements of the NFPA 70E

Table 130.7 (C) (10) and 130.7 (C)(11).

 

 

The information regarding NFPA 70E contained in this website is condensed for brevity. Users should consult the NFPA 70E

document for complete information.

NFPA 70E is available from the National Fire Protection Association (www.nfpa.org).

 

Information presented is used with permission from Chicago Protective Apparel, a leading manufacturer of arc flash

protective apparel.