A better understanding of NFPA 70E: Where did the 40 cal/cm2 limit go?
There must be an increase in the need to perform justified, energized work on equipment with high incident energy levels. Questions have come in regarding the restriction for incident energies above 40 cal/cm2. Many believed that NFPA 70E®, Standard for Electrical Safety in the Workplace® requirements “really” only applied above 40 cal/cm2. Others believed the standard did not cover incident energies above 40 cal/cm2. It took some time to realize what everyone was considering to be a restriction. Prior editions of NFPA 70E contained an informational note that stated when incident energy exceeded 40 cal/cm2 at the working distance, greater emphasis may be necessary with respect to de-energizing when exposed to electrical hazards. The purpose of this note was to re-emphasize the requirements of the standard. Establishing an electrically safe work condition (ESWC) was and still is required regardless of the incident energy. One problem with the informational note was that many where incorrectly interpreting it to mean that it wasn't necessary to worry about incident energies below 40 cal/cm2. These people felt that this note meant that an ESWC was not “really” necessary or required until 40 cal/cm2. Below this level it was just a suggestion to establish an ESWC. This may be why I receive so many questions about using PPE when working on energized equipment rather than establishing an ESWC. Those who Another group was interpreting the informational note to mean that NFPA 70E placed a limit on the permissible incident energy. The PPE category tables are limited to address equipment that is permitted to be worked on while wearing at least 40 cal/cm2 gear. If you have equipment that is listed on the PPE category tables but the specified parameters are not met then the equipment must be evaluated under the incident energy analysis method. There is no limit to the incident energy that can be calculated. However, finding PPE rated to protect at high energy levels may be difficult. Misuse of the standard and specifically of the 40 cal/cm2 informational note is one reason for the removal of that informational note. Once you have a system that exceeds the threshold limits in NFPA 70E, you must minimize the hazard and risk that hazard presents to your employees. An electrically safe work condition must be established if an employee is to enter the limited approach boundary. NFPA 70E is about protecting the worker from injury but there may not be equipment available to protect from all levels of a hazard. That is one area where the hierarchy of risk controls comes into play. Although there is no limit to the amount of incident energy that may present, if energized work is justified, you are responsible for protecting your employees from whatever level of hazard exists. For more information on 70E, read my entire 70E blog series on Xchange. Please Note: Any comments, suggested text changes, or technical issues related to NFPA Standards posted or raised in this communication are not submissions to the NFPA standards development process and therefore will not be considered by the technical committee(s) responsible for NFPA Standards development. To learn how to participate in the NFPA standards development process and submit proposed text for consideration by the responsible technical committee(s), please go to www.nfpa.org/submitpi for instructions.