Protection from Flames and Electric Arcs
It is important to remember that all arc hazards are not equal.
According to OSHA, electric power generation, transmission and distribution workers face a significant risk of injury from burns due to electric arcs. Studies have concluded that a large percentage of arc-related incidents resulted in either a fatality or in extremely painful third-degree burns, which require skin grafts and leave permanent scarring. Based on these conclusions, OSHA adopted standards to address forms of personal protective equipment other than clothing. These standards – titled “Protection from flames and electric arcs” and found at 29 CFR 1910.269(l)(8) and 1926.960(g) – require employers to assess the workplace for hazards associated with flames and electric arcs and to provide PPE to employees who will have exposure. Since these standards require PPE, the employer is obligated to purchase and ensure appropriate maintenance of that PPE.
Utilizing the hierarchy of controls is necessary to eliminate or effectively control hazards. Since that’s the case, why would OSHA design a standard that specifically addresses PPE, the last line of control? OSHA addresses this concern in the preamble to the final rule by stating that “the final rule protects employees in case an electric arc occurs in spite of other provisions in the final rule designed to prevent them from happening in the first place.” Plainly speaking, OSHA designed the entire electric power standard for the prevention of flames and electric arcs, so the PPE portion of the standard is designed to be the last line of control in case all else fails.
Five important requirements are found within this standard. These can be met by using Appendix E to both 1910.269 and 1926 Subpart V, “Protection From Flames and Electric Arcs.” The requirements are as follows:
- Assess the workplace for hazards from flames or electric arcs.
- Estimate the incident energy when there is exposure.
- Prohibit specific clothing when incident energy could ignite that clothing.
- Require flame-resistant clothing under certain conditions.
- Select clothing with an arc rating greater than the estimated incident energy.
OSHA requires employers to assess the workplace to identify employees who have exposure to hazards from flames and electric arcs. A hazard assessment includes identifying potential sources along with the completion of a risk assessment to determine the probability and severity of the potential exposure.
Appendix E to 1910.269 and 1926 Subpart V identifies sources of electric arcs as unguarded, uninsulated live parts; switches that arc in normal operation; sliding parts subject to faults; and electric equipment subject to failure. Sources of flames include open flames and ignitable material near flames or arcs. It is important to remember that the employer is responsible for determining sources, so this should not be considered an exhaustive list.
Appendix E also identifies the probability of an occurrence to include whether conductive objects can fall on live parts; whether an employee is inside the minimum approach distance; whether operation of electric equipment is part of a normal operation or occurs during servicing; and whether there is evidence of impending failure.
It is important for employers to use a developed process to appropriately determine potential sources and assign risk. Without an effective hazard identification process, employers may place focus on the use of PPE instead of hazard mitigation.
Estimated Incident Energy
It is important to remember that all arc hazards are not equal. Therefore, electric power organizations can’t just address arc hazards the same way as the neighboring utility does. OSHA requires employers to estimate the potential amount of incident energy available at work locations. Incident energy is a measure of thermal energy at a working distance from an arc fault. The unit of measurement for incident energy is known as cal/cm2. Working distance is an extremely important component of incident energy levels because the levels decrease as an employee moves away from the arc source.
OSHA does not require employers to estimate incident energy exposure for every job task. Broad estimates that cover multiple system areas can be used to provide reasonable assumptions. Table 3 of Appendix E outlines the appropriate engineering methodology utilized to determine incident energy levels. This table provides employers with the engineering methodology for various types of arc hazard exposures, including single-phase open air, three-phase open air and three-phase in an enclosure. It is important to verify appropriate calculation methods to provide appropriate incident energy values for the work to be performed.
Remember that an electric power system is constantly changing and updating, so it is important to regularly review engineering analyses to ensure incident energy levels are accurate for the work to be performed. Additionally, host employers are required to furnish incident energy levels and/or required PPE to affected contractors as a part of information transfer requirements.
Where arc hazards exist, workers are prohibited from wearing clothing made from acetate, nylon, polyester, rayon or polypropylene, either alone or in blends. Garments to be used must have an effective arc rating.
OSHA requires the outer layer of clothing to be flame-resistant when an employee is exposed to contact with energized circuit parts greater than 600 volts when an electric arc could ignite flammable material in the work area, and when molten metal or electric arcs from faulted conductors could ignite clothing.
Additionally, employers are required to provide arc-rated PPE when employee exposures exceed 2 cal/cm2. The expectation is that PPE with an arc rating equal to the estimated incident energy will be capable of preventing a second-degree burn injury to an employee exposed to the incident energy from an electric arc. OSHA requires that arc-rated protection cover the employee’s entire body, with limited exceptions for the employee’s hands, feet, face and head. Appendix E identifies those exceptions in an easily accessible format.
It is especially important to ensure employees do not wear undergarments made from prohibited clothing even when the outer layer is flame-resistant or arc-rated. The undergarments can melt or easily ignite when an arc occurs. Logos and tags made from non-FR material can also adversely affect the arc rating or FR characteristics.
Always remember that all arc hazards are not equal. Electric power organizations have a responsibility to provide an effective hazard control process as well as the appropriate FR and arc-rated PPE.
The industry has become more proactive by developing new design and engineering controls to reduce arc hazards. In addition, arc-rated PPE has greatly improved over the years, making it easier to wear correctly.
About OSHA Electric Power Standards – Simplified: Topics in this series are derived from SET Solutions’ popular OSHA electric power course offered through the Incident Prevention Institute (https://ip-institute.com). The course is designed to help learners identify standard requirements and to offer practical ways to apply the standards.