What to Wear to Work

While OSHA has clarified its position on PPE for electrical workers, employers still have work to do before they can tell employees what to wear and when.

Arc flashes occur when electrical current jumps the gap between two or more energized conductors. Depending upon the amount of current, arc temperatures can exceed 35,000 degrees F. That’s why electrical workers must wear fire-resistant (FR) personal protective equipment when working near exposed, energized equipment.

OSHA recently clarified the responsibility of employers to provide PPE, such as FR clothing, to electrical workers. Actually, the requirement for employers to assess hazards and select PPE has been in place since 1990, yet some workplace managers have not provided FR clothing to electrical workers—and if they do, they fail to train workers on what to wear based on the task and the Hazard Risk Category at the equipment on which they may work.

OSHA’s 1910.132(d) requires employers to assess for workplace hazards and select appropriate PPE. It’s not enough to give workers an FR shirt and insulated pliers. Instead,OSHA requires the employer to train workers on what to wear for each task at each piece of equipment.

OSHA requirements cover “Qualified Workers” who work on or near electrical hazards. NFPA 70E, the consensus standard for electrical safety to which OSHA adheres, defines Qualified Workers as those workers having skills and knowledge related to the construction and operation of the electrical equipment, and who have received documented safety training on the hazards involved. OSHA and NFPA 70E minimum training requirements for Qualified Workers include the ability to distinguish exposed live parts from other parts and how to determine the nominal voltage of exposed live parts. They also must understand the Flash Protection Boundary (the distance from the equipment at which a second-degree burn can occur to unprotected skin) and the Hazard Risk Category at each piece of energized equipment.

The Hazard Risk Category and the degree of FR protective clothing  for various Arc-Flash exposures are dictated by the amount of heat (measured in calories per square centimeter) that may be generated at the working distance. The amount of heat, in turn, depends on the potential fault current and length of time (number of AC cycles) it takes for the fuse, circuit breaker, or other protection device to cut off the power (fault clearing time).

NFPA 70E requires the worker to wear clothing with an Arc Rating that exceeds the calculated heat exposure or the minimum PPE rating for the Hazard Risk Category listed in Table 1.

Additional PPE Types
In addition to properly rated FR clothing, the worker may be required to wear various other types of PPE, including safety glasses, safety shoes, hard hat, faceshield, multi-layered switching hoods, and hearing protection (see Table 4). If work will be performed on exposed, energized equipment within the Restricted Approach Boundary, the qualified worker must also use V-rated (voltagerated) rubber gloves and V-rated tools tested for the maximum line-to-line voltage. Leather protectors should be worn externally ifV-rated rubber gloves could be damaged or when work is performed on equipment rated HRC 2 and above.

The Hazard Risk Category is key. Unlike many workers who wear the same kind of clothes to work every day, an electrical worker must dress differently for an electrical panel labeled Hazard Risk Category 4 than for one labeled a less hazardous Hazard Risk Category 1. So to know what to wear, you must first determine the possible incident energy and Hazard Risk Category.

Determining Hazard Risk Category
NFPA 70E gives two ways to determine the Hazard Risk Category: One way is to conduct an Arc-Flash Hazard Analysis involving engineering calculations and physical inspection of the electrical system. The other way is to use the so-called “Table Method.” NFPA 70E Table 130.7(C)(9)(a) lists typical tasks that electrical workers might perform on different classes of energized equipment rated from 50V to 1kV and above and assigns a Hazard Risk Category for each task.

It seems simple, but there’s a catch. Use of the table is permitted only when the available fault current and clearing time of circuit protection devices are known. If the notes and disclaimers listed in the table are not verified and documented, Hazard Risk Categories, PPE requirements, and Flash Protection Boundaries derived from the table may be inadequate to protect workers when the actual hazard conditions occur.

Also, if the employer chooses to use the Table Method instead of conducting an Arc- Flash Hazard Analysis, then workers must wear clothing and other PPE that meets the minimum requirement for the assigned Hazard Risk Category. Performing the engineering calculations instead of using the table ensures that workers avoid being encumbered by unnecessary gear.

An Arc-Flash Hazard Analysis involves gathering complete, up-to-date details of the electrical system including one-line diagrams, calculating available fault currents where workers may be exposed to contact with energized conductors, analyzing the clearing times of overcurrent protective devices, and performing a coordination study of those devices. Typically, the analysis is performed by a qualified engineering services firm.

After the data are compiled, it is possible to calculate the level of potential “incident energy” that could be released at each piece of equipment where an arc flash may occur. Incident energy is determined by the available fault current and the clearing time and coordination of the circuit protection devices (fuses, circuit breakers, etc.). The amount of potential incident energy determines the Hazard Risk Category, which in turn determines the types of PPE that workers must use before they can safely approach energized equipment.

Dressed For Success
For electrical workers, safety on the job begins when they get dressed at home. Street clothes are actually the first layer of protection against the heat of an arc flash. In addition to any required PPE, an electrical worker is expected to wear natural-fiber (usually cotton) street clothing and underwear. Synthetic fibers such as nylon and polyester are not allowed because they may melt and adhere to the skin, resulting in secondary burns. Proper street clothes can be required as a condition of employment, in the same way that a suit is the dress code in some offices. Some employers may choose to provide uniforms to take the place of street clothing.

As shown in Table 4 ,Hazard Risk Category-mandated clothing includes a variety of FR shirts, pants, coveralls, and flash suits. For the lower categories, everyday wear may be sufficient. For higher Hazard Risk categories, multi-layer flash suits may be necessary. The chart shows the required PPE for the various Hazard Risk Categories. Multiple layers of FR protective clothing may be worn to meet Hazard Risk Category requirements. When multiple layers are worn, the rule of thumb is that the cal/cm2 is determined by totaling the ratings of the individual layers and adding 50 percent to the total. (This presumes that the air space between the layers has insulating value, thus increasing the protection.)

For example, if a 4-calorie long-sleeved shirt is worn over an identical long-sleeved 4-calorie FR shirt, the combined cal/cm2 rating may be 4+4 = 8+4 (50 percent) = 12 cal/cm2. Managers should check with the PPE manufacturer if verified by testing before purchasing.

The employer or worker may select a coverall and/or multi-layer flash suit with a higher rating than that prescribed for the Hazard Risk Category and be in conformance. However, while wearing PPE with higher ratings can be an “easy” way to meet Hazard Risk Category requirements, it may not be easy for the worker to work in it, and it increases employer costs.

Tell Workers About the Hazard
OSHA standards require employers to train workers about electrical hazards and how to avoid them.As previously stated, the Hazard Risk Category determines the PPE that electrical workers must wear when working on or near exposed, energized equipment within the Flash Protection Boundary. The surest way employers can convey what PPE is required is to label electrical equipment with the possible incident energy and Hazard Risk Category.

OSHA and NFPA 70E standards recognize National Electrical Code Article 110.16 which details the requirements for Arc-Flash warning labels. If the equipment is likely to require examination, adjustment, service, or maintenance while energized, it must be labeled by the employer. The new edition of NFPA 70E due out sometime in 2008 will require the Incident Energy and Hazard Risk Category to be prominently displayed on warning labels.

If equipment is not marked or labeled, such omission may be used as evidence of employer negligence if workers are injured. In addition to arc flash and shock warnings, labels should also identify Shock Protection Boundaries, Flash Protection Boundaries, Hazard Risk Category, and required PPE.

After or before labeling,workers must be trained how to dress for each hazard, and such training must be documented.

Another way to communicate potential Arc-Flash Incident Energy and Hazard Risk Category to workers is in an Energized Electrical Work Permit. NFPA 70E Article 130.1(A) details the use of work orders, which describe the task to be performed, the Hazard R isk Category, the required PPE, the reason why the equipment cannot be de-energized, and other requirements.

Easiest Risk to Avoid
Proper safety hazard assessments, safety training, use of proper PPE, adherence to operating procedures, and documentation are specifically required by NFPA standards. Be sure you understand these requirements and be sure you are qualified to initiate and maintain the programs necessary to ensure compliance. If not, don’t risk worker injury, sizable fines, liability, equipment costs, and work stoppages. It is far easier to seek out qualified assistance from an engineering services firm with demonstrated experience and which is familiar with your type of facility, processes, safety requirements, and industry-specific requirements.

This article originally appeared in the June 2008 issue of Occupational Health & Safety.

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