An arc flash occurs when an electrical current leaves its intended path and travels from one conductor to another. This may result in fire, flying objects (traveling at more than 700 mph), blast pressure, sound blast (exceeding 160 dB) and heat (exceeding 30,000 F). If an arc flash makes contact with a person, injury and death may occur depending on proximity of the worker to the source, temperature, and time for the circuit breaker to be disengaged. OSHA last issued an arc flash related rule in 1972.
In April 2014 OSHA issued a new final ruling that harmonizes OSHA 29 CFR parts 1910 and 1926, increases safety, and addresses electrical workers. Workers will be required to wear clothing that covers and protects potentially exposed areas as completely as possible when arc flash hazards may be present. The new OSHA ruling is being implemented in three phases:
- Estimate Available Heat Energy – Required to meet 29 CFR 1910.269(1)(8)(ii) and 29 CFR 1926.960(g)(2) by March 31st, 2015. What this means to you: employers must assess heat energy risk.
- FR Clothing – Required to meet 29 CFR 1910.269(1)(8)(iv)(A) through (1)(8)(iv)(C) and 29 CFR 1926.960(g)(4)(i) through (g)(4)(iii) by April 1st, 2015. Clothing must be non-melting, not contribute to the extent of the injury and must not ignite and continue to burn when exposed to electric arcs. An exception used to exist that permitted non-FR jeans greater than 11 oz. This is no longer the case.
- Arc-Rated Protection – Required to meet 29 CFR 1910.269(1)(8)(v) and 29 CFR 1926.960(g)(5) by August 31st, 2015. Though no citations will be issued to employers failing to provide personal protective equipment (ppe) rated higher than 8 cal/cm squared.
FR Versus Arc Flash Rated Clothing
All arc flash rated clothing is FR (Flame-Resistant) but not all FR clothing is arc flash rated. FR clothing is often but not always rated as HRC 2 (minimum performance of 8 cal/cm2) and referred to as daily wear. FR clothing is required when working on energized equipment greater than or equal to 600 V, clothing ignition is possible directly or indirectly in the work area or when the potential for exposure to more than two cal/cm squared exists.
Rules for Base Layers and Body Protection
Clothing ignition is still possible when wearing FR and arc flash rated workwear. FR and arc flash rated clothing may not have openings that expose flammable layers if the clothing would be "unable to resist breakopen". This means sleeves must be fastened to wrists, be tucked in, collars buttoned, etc. When layering arc flash rated apparel, the overall level of heat or calorie protection isn't the sum of the individual layers. The user may also require personal protective equipment for the head and face for total compliance.
Rules for Head Wear and Personal Protective Equipment (PPE)
The table below identifies the minimum head and face protection required based on levels of exposure to arc flashes. Head and face protection may include faceshields, hoods, and balaclavas.| Incident Energy | Exposure | Minimum Head and Face Protection |
|---|---|---|
| 2-8 cal/cm2 | Single-Phase, open | None (except hard hat) |
| 2-4 cal/cm2 | Three-Phase | None (except hard hat) |
| 9-12 cal/cm2 | Single-Phase, open | Arc-rated faceshield with a minimum rating of 8 cal/cm2 |
| 5-8 cal/cm2 | Three-Phase | Arc-rated faceshield with a minimum rating of 8 cal/cm2 |
| 13 cal/cm2 or higher | Single-Phase, open | Arc-flash rated hood or faceshield with balaclava |
| 9 cal/cm2 or higher | Three-Phase | Arc-flash rated hood or faceshield with balaclava |
It is likely that workers will require multiple garments (clothing, head wear, etc) to maintain safety while performing multiple tasks. Now it's time to check for compliance.
How to Comply With OSHA
After your company identified potential sources of arc flashes in the workplace, you ensured your team was wearing FR clothing when appropriate. Now it's time to review your company's inventory and check clothing labels for compliance. Arc flash ratings may be substituted for Arc Thermal Protective Value (ATPV) on apparel tags. Clothing may also feature a Hazard Risk Category (HRC) representing the minimum levels of protection:| Hazard Risk Category | Minimum Performance |
|---|---|
| HRC 1 | 4 cal/cm2 |
| HRC 2 | 8 cal/cm2 |
| HRC 3 | 25 cal/cm2 |
| HRC 4 | 40 cal/cm2 |
You may also see NFPA 70E or ASTM on clothing labels indicating a flame resistant item being defined in arc rated industry standards. For example a clothing article that's NFPA 70E and ASTM 1506 (clothing) rated will be able a sustain a flame without damaging more than six inches of the item, doesn't have an afterflame that lasts more than two seconds and doesn't lead to melting or dripping. This is tested with the ASTM D6413 Vertical Flame method.
Your company may need to purchase new or additional arc flash rated clothing. If you have questions or would like assistance in picking out appropriate clothing, please don't hesitate to give one of our safety experts a call at 800-829-9580.
Additional Resources: Arc flash incident energy and protection boundary calculator Choosing an arc flash analysis vendor Removal of arc flash hazards