Using Dielectric and Electrical Hazard Shoes
Minute holes in the soles of the footwear are the biggest area of concern in the protection scenarios.
- By Hugh Hoagland
- Apr 01, 2011
There are two basic names for shoes that have some protection from electrical shock: Dielectric (DI) and Electrical Hazard (EH) rated. The differences between the standards are not usually understood, even by electrical specialists. Few guidelines exist on when and where to use the shoes in either standard. This paper offers some assistance on which standards relate to which shoes.
Hazard Assessment Guides
OSHA PPE General Guide
According to 29 CFR 1910.136(a): "Each affected employee shall wear protective footwear when working in areas where there is a danger of foot injuries due to falling or rolling objects, or objects piercing the sole, and where such employee's feet are exposed to electrical hazards." Appendix B of Subpart I identifies the following occupations for which foot protection should be routinely considered: shipping and receiving clerks, stock clerks, carpenters, electricians, machinists, mechanics and repairers, plumbers, assemblers, drywall installers and lathers, packers, wrappers, craters, punch and stamping press operators, sawyers, welders, laborers, freight handlers, gardeners and grounds keepers, timber cutting and logging workers, stock handlers and warehouse laborers.
OSHA 29 CFR 1910.269, which applies to the transmission, distribution, and generation of electricity, cites ASTM F1117 shoes in the standards document but gives no guidelines as to when they are needed.
An OSHA interpretation letter from March 17, 1993, basically does not "require" electrical trades to wear "safety toed shoes." The letter states, "One option you and your employer may wish to consider is the purchase of non-metallic safety footwear that provides both foot protection and is non-conductive." No later opinions have been offered.
OSHA gives little guidance and really mentions the EH shoes only in the general PPE guide for small businesses. OSHA states, "Electrical hazard, safety-toe shoes are nonconductive and will prevent the wearers' feet from completing an electrical circuit to the ground. These shoes can protect against open circuits of up to 600 volts in dry conditions and should be used in conjunction with other insulating equipment and additional precautions to reduce the risk of a worker becoming a path for hazardous electrical energy. The insulating protection of electrical hazard, safety-toe shoes may be compromised if the shoes become wet, the soles are worn through, metal particles become embedded in the sole or heel, or workers touch conductive, grounded items. Note: Nonconductive footwear must not be used in explosive or hazardous locations."
NFPA 70E Guidelines
NFPA 70E attempts to give guidelines for using DI or EH shoes, but it suffers from some of the same issues as the OSHA guides. It is better in the sense that it does make use mandatory in a few cases but is still unclear about the role, if any, for EH shoes.
Electrical Hazard (EH) Shoes
Table 130.7(C)(8) Standards on Protective Equipment lists both ASTM F1117 and F2413 under the footwear section but does not mention EH shoes. The ASTM F1117 standard is cited by the F2413 standard as the standard specification for DI shoes, so the citation of F2413 does not imply that EH shoes are required by NFPA 70E.
Table 130.7(C)(10) Protective Clothing and Personal Protective Equipment (PPE) calls for all Hazard/Risk Categories (HRC) to include "leather shoes," which in no case can be dielectric shoes. "Leather shoes" are not equivalent to "EH" shoes.
130.7(C)(13)(d) "Foot Protection. Heavy-duty leather work shoes provide some arc flash protection to the feet and shall be used in all tasks in Hazard/Risk Category (HRC) 2 and higher and in all exposures greater than 4 cal/cm²." This would imply that DI shoes alone are not acceptable but does not exclude EH shoes.
Dielectric (DI) Shoes
"130.7(C)(7) Foot Protection. Where insulated footwear is used as protection against step and touch potential, dielectric overshoes shall be required. Insulated soles shall not be used as primary electrical protection."
130.5(E)(3) Dielectric overshoes are required when performing "equipment grounding near power lines."
Only dielectric footwear is listed in 250.1 Maintenance Requirements for Personal Safety and Protective Equipment.
320.8 Personal Protective Equipment for Battery Rooms requires protective overshoes but doesn't indicate why they are used. If they are for acid protection, then they would need to meet an applicable part of F2413. But if for electrical hazards, they would need to meet ASTM F1117.
In 310.5 (D)(2)(1) for protecting employees working around electrolytic cells, such as in smelting operations, shoes are listed for "wet service" and if 130.7(C)(7) is understood, the use of dielectric shoes/overshoes or boots is required.
NFPA 70E Guideline Summary
Dielectric shoes are required for wet service and step potential hazards in any application and EH shoes are optional, but leather is mandatory in HRC 2-4.
OSHA Guideline Summary
OSHA letters of interpretation present EH shoes positively but do not require them. In higher voltages or higher risks (1910.269), OSHA cites ASTM F1117 for dielectric shoes -- not ANSI Z41 or ASTM F2413.
ANSI Z41 was the old, general safety shoe standard. It used to include EH shoes, but now shoes must meet ASTM 2413-2005.
The ASTM F2413-05 standard covers minimum requirements for the design, performance, testing, and classification of protective footwear. Footwear certified as meeting ASTM F2413-05 must meet the minimum requirements of Section 5.1 "Impact Resistant Footwear" and Section 5.2 "Compression Resistant Footwear." Additional sections have requirements of specialty shoes, such as metatarsal protection, conductive protection, electric shock protection, static dissipative protection, and protection against punctures. ASTM specification must be marked with the specific portion of the standard with which it complies. One shoe of each pair must be clearly and legibly marked (stitched in, stamped on, pressure sensitive label, etc.) on either the surface of the tongue, gusset, shaft, or quarter lining.
An example of ASTM style markings for protective footwear is:
First line: ASTM F2413-05 means the protective footwear meets the performance requirements of ASTM F2413 issued in 2005.
Second line: M I/75 C/75 Mt75. M in this case means the footwear is designed for a Male (F would be Female). I denotes impact resistance followed by the impact resistance rating (75 or 50 in foot-pounds). C denotes compression resistance and the compression resistance rating (75 or 50, which correlate to 2,500 pounds and 1,750 pounds of compression, respectively). Mt means this shoe has metatarsal protection and rating (75 or 50 foot-pounds).
Third and optional fourth line: PR EH. The last two lines are used to identify footwear made to offer protection from other specific types of hazards referenced in the standard. They designate conductive (Cd) properties, electrical insulation properties (EH), static electricity dissipative (SD), puncture resistance (PR), chainsaw cut resistance (CS), and dielectric insulation (DI), if applicable. The last line is used only when more than three sections apply.
Electrical Hazard (EH) footwear is manufactured with non-conductive, electrical shock-resistant soles and heels. The outsole can provide a secondary electrical shock resistance protection to the wearer against the hazards from an incidental contact with energized electrical circuits or parts. Testing ensures the materials are capable of withstanding 14,000 v at 60 Hz for one minute with no current flow or leakage current in excess of 3.0 mA, under dry conditions. (This is not usually acceptable for wet service or higher voltages.). ASTM 2413 cites ASTM F1117 for dielectric shoes.
CAN/CSA-Zl95-M92 Section 4.3 is similar to the ASTM 2413 standard but more stringent in its leakage and voltage requirements. The CSA standard is also a "wet sole test."
ASTM F1116-03 (Reapproved 2008) is the ASTM test method for dielectric shoes. It has three procedures that differ according to the section of the footwear tested. (To purchase ASTM standards, see http://www.astm.org/.)
ASTM F1117-03 (Reapproved 2008) is the specification for dielectric footwear and is a quite stringent standard. Only one boot and overshoe currently meets the F1117-08 specification.
The most important thing to be aware of is that ASTM F2413 is a standard designed primarily for impact and compression protection. Some dielectric shoes cannot pass the compression portion of that standard because many are designed as overshoes and don't have a steel toe, but the overshoes can be worn with compression-resistant shoes if needed.
Note: Steel toes have never been shown to conduct electricity as long as the toe is still covered with the shoe material.
ASTM F-1117 refers to the boots and overshoes as "supplementary protection" because the shoes have no "in-use" standard. In-use standards normally require re-testing, so shoes should never be relied on as primary protection. An in-use standard is not planned at the current time by the ASTM F18 committee.
Which Standard Do I Choose?
First, choose the protection level or specific standard you need: Dielectric or Electrical Hazard levels. Second, choose the standard: ASTM F1117, ASTM F2413, or CSA Z41. Third, look into the unique hazards of the work environment. The higher the overshoe, the less likely it is that water, grass, or other energized materials contact the worker. Also, look closely at the heel and sole design. This is especially true for climbing poles, ladders, and stairs. A deep heel is needed to climb safely, while the normal shallow heel works well for walking. Fit and the ease of donning and doffing the footwear warrant consideration, especially on overshoes.
Problems to Consider
Most testing applies only to the sole of the footwear, which usually begins degrading quickly. Minute holes in the soles of the footwear are the biggest area of concern in the protection scenarios. Footwear, unlike the rubber gloves used for primary protection in utilities, has nothing to protect it from the effects of walking and from the effects of ozone and UV light. The makers and users of dielectric shoes point out this fact. They also note that some utilities attempt to lessen the chances of sole degradation by stamping a date on the footwear and replacing them after one year or less, depending on the frequency of use. All manufacturers and users recommend regular visual inspections and replacement when any sign of excessive wear exists.
With OSHA early documents falling on the side of EH shoes for electrical work, companies would do well to consider them for all electrical workers and other workers exposed to electrical hazards or damp locations. These shoes rarely add more than $5 to the cost of the shoe and have been known to save lives. They should be considered for low-voltage (<750V) and low-risk tasks.
High-risk tasks, environments, and medium and high voltages require more and more stable protection. ASTM F1117 shoes provide this type of protection and are the preferred step potential PPE option in both OSHA 1910.269 and NFPA 70E.
This article originally appeared in the April 2011 issue of Occupational Health & Safety.
Hugh Hoagland, CESCP, IEEE (SM), is among the world's foremost experts on arc testing and electrical safety. He is the senior managing partner and co-founder of e-Hazard, a leading electrical safety training and consulting firm, and the founder of ArcWear, which does 90 precent of the world's arc flash testing of protective apparel. As an R & D Director at NASCO, he helped invent arc-rated raingear and arc flash faceshield materials, and he holds several patents related to arc flash protection. Hugh serves on many international standards committees including NFPA, ASTM, IEEE, IEC, and has helped develop electrical and flash fire safety legislation and standards in the U.S., Europe and internationally. He has trained over 50,000 line-workers, managers, and electricians at large electric users and electric utilities and is a featured speaker at safety conferences. He is an associate editor for the IEEE Electrical Safety Committee and a Senior Member of IEEE, and has published more than 60 articles and papers on arc flash, electrical safety, and PPE.