Arc flash hazard experts answer your questions

May 12, 2011
Our panel of industry experts answers your arc flash hazard questions about NFPA 70E, PPE and much more.

Mitigating the risk of arc flash hazard requires a plan. NFPA 70E is a standard for electrical safety in the workplace that was developed by the National Fire Protection Association in 2009.

On March 31, Patrick Ostrenga, compliance assistance specialist, U.S. Department of Labor-OSHA (, Dennis Neitzel, C.P.E., director emeritus, AVO Training Institute ( and Rick Maday, marketing specialist, Fluke (, participated in the Plant Services Arc Flash Hazard Webinar and discussed what companies are doing to mitigate the hazard of arc flash. This webinar identified best practices and demonstrated the technologies companies are using to determine a path toward a safer work environment.

Because of the overwhelming participation in our webinar, our panel of experts were unable to answer all of the questions in the allotted time. Below are the answers to those questions. In addition, we’ve scheduled to more webinars on arc flash hazard on August 18 and November 10.

Question: Is adaption of NFPA 70E standards an option? My manager thinks it is. Your comments?

Neitzel: NFPA 70E is a consensus standard, and therefore it is optional. However, it provides the path for compliance with OSHA 1910.331-.335 and has been used as a reference in OSHA citations, as well as by civil litigation court cases. NFPA 70E is also a reference listed in OSHA STD 1-16.7, Electrical Safety-Related Work Practices – Inspection Procedures and Interpretation Guidelines of the Directorate of Compliance Programs. It would be wise to adopt and use NFPA 70E because you will be held accountable for the requirements contained therein.

Question: We work in a lead environment and are required to wear full face respirators. Are there any full face respirators that rated to arc flash hazard ratings?

Neitzel: I am not aware of any. A search on the Internet and with respirator manufacturer is recommended.

Question: Is an MCC panel bucket considered deenergized by opening the circuit breaker, even if the line side of the breaker remains energized but is not exposed?

Neitzel: Yes and no. When the breaker is open, the line voltage is removed. However, there is control and interlock voltages still present in the bucket. If contact might be made, then it is still energized work. With the breaker off, the shock hazard may be eliminated or minimized but the arc flash hazard still exists unless the entire MCC is deenergized and controlled, so PPE is still required.

Question: What protection is offered to a worker who refuses to perform dangerous work based on NFPA 70E standards?

Neitzel: I don’t fully understand the question. Is it asking for legal protection? NFPA 70E provides the requirements for electrical hazard analysis, electrical safety programs, procedures and work practices, employee training and PPE so there is no reason for an employee to “refuse” to work on electrical equipment unless the employer is refusing to comply with the NFPA 70E requirements.

Question:. Do you have comments on the following? According to the hazard analysis, to perform work on exposed energized parts of a 480-V motor control center, 40-cal PPE must be worn. This is understandable. However, when wearing this PPE to perform voltage testing, it is impossible to see what you are doing. The face shield is too dark to see the meter leads and the meter readout. Yet, voltage testing needs to be performed for troubleshooting. It seems that this would pose more of a hazard.

Neitzel: If the “hazard analysis” requires a 40 cal/cm2 flash suit, then it must be worn. If the face shield makes it too dark to read the meter, then auxiliary lighting must be used.

Question: Can an operator turn on motor starters without the proper PPE for the category risk factor from the arc flash analysis study?

Neitzel: No. Regardless of who is interfacing with the equipment, the proper PPE must be used, based on the hazard analysis. Training must be provided for operators or anyone else who is required to interface with energized electrical equipment so that they understand the hazards and the reasons for using PPE.

Question: I am a subcontractor to a company which attempts to use the tables in 130.7 to perform energized work even though the equipment does not meet the FPN notes, i.e., fed from a 2,500 KVA transformer.Your thoughts?

Neitzel: If the notes to Table 130.7(C)(9) are not used, then the table cannot be used and an arc flash hazard analysis must be completed and arc flash warning labels installed on the equipment by the equipment owner. If the owner, or host, does not perform the hazard analysis and install the labels, the contractor has no choice but to use Table 130.7(C)(9) at face value, without using the notes, in order to provide at least a level of protection for his or her employees. The contractor will generally not know what the available short-circuit current or protective device clearing time is.

Question: Does IR window need any periodic maintenance?

Maday: No periodic maintenance is needed. Depending on the environment, typically extremely dusty, in which the enclosure the IR window is installed on, you may need to clean dust from the inside of the viewing pane during shutdowns when the enclosure is open for maintenance.

Question: How can we calculate the blast pressure resistance of an IR window? If so how?

Maday: Pressures change panel to panel. If your panel is not "arc-resistant" then the resistance of the IR window to arc-flash is likely greater than the panel itself. To calculate the resistance of an IR window to arc flash the most useful measure is the calorie withstand capability of the optic. This can be calculated using your plants adopted arc-flash calculation protocol and the IR window testing data.

Question: Will there be more arc flash definition on control panels rather than distribution equipment?

Neitzel: Typically a control panel does not have an arc flash hazard, if it contains only control devices and voltages. The distribution equipment (MCC, panels, disconnects) typically have an arc flash hazard and must be analyzed.

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