Read this before you rely on anything here.

§ How to use it

• Work from the published standard. NFPA 70E 2027, the NEC edition adopted by your jurisdiction, and 29 CFR 1910 and 1926 are the authoritative documents. This site cites them so you can go and read them.
• Work from your own arc flash study. Incident energy, boundaries and PPE for your installation come from an engineering analysis of your system, not from a web page.
• Work from your employer's electrical safety program. Where your program is more restrictive than the standard, follow your program.
• The tools show method, not verdicts. They are teaching aids that walk the logic of the standard. They do not know your equipment.

§ Accuracy

• Content is written and reviewed by Rick Hauf, CSP. Errors are possible; if you find one, tell us and it will be corrected.
• Standards revise. NFPA 70E is on a three-year cycle. Content here is written against the 2027 (14th) edition. Verify against the current published edition.
• Table values reproduced here are summarised and rounded for readability. Read the published table for the condition you are actually in.
• Where a point is genuinely unsettled or awaiting confirmation against the published standard, it is marked [verify] on the page.

§ Legal

• No attorney-client, engineer-client or consultant-client relationship is created by using this site.
• Nothing here is legal advice. Regulatory obligations vary by jurisdiction, including in the roughly half of US states operating their own OSHA-approved state plans.
• NFPA 70E®, NFPA 70® and National Electrical Code® are registered trademarks of the National Fire Protection Association. This site is not affiliated with, endorsed by, or sponsored by NFPA.
• This site is not affiliated with, endorsed by, or sponsored by OSHA or the US Department of Labor.
• Mission Critical Safety works to United States standards — NFPA and OSHA. It is unrelated to similarly named entities operating to EU or IEC standards.

§ If someone is hurt