NFPA 70E is the National Fire Protection Association's Standard for Electrical Safety in the Workplace. It is the consensus standard employers use to protect workers from shock, arc flash and arc blast when they work on or near electrical equipment. An arc flash is an electrical explosion: OSHA's arc flash guidance notes that temperatures in the arc can exceed 35,000°F.
For a building owner or property manager, the practical duties are simple to state. Know what equipment you have. Keep it maintained and documented. Label it. And do not put anyone, your own staff or a contractor, in front of energized gear without a plan. This guide explains how 70E relates to OSHA, what arc flash labels and studies are, and what an owner can do without becoming an electrical engineer.
What NFPA 70E is, and how it relates to OSHA
NFPA 70E is not the building code. The National Electrical Code (NFPA 70) governs how electrical systems are installed. NFPA 70E governs how people work on them safely once they exist: when equipment must be de-energized, how the hazard is assessed, what protective equipment is needed, and how energized work is justified and controlled.
OSHA does not enforce NFPA 70E directly. In a formal interpretation letter, OSHA explained that it has not adopted the later editions of 70E through rulemaking and therefore does not "enforce" them. It also said its Subpart S safety-related work practices were based on the 1983 edition of NFPA 70E, and that consensus standards such as 70E can be used by OSHA and employers as guides for hazard analysis and control measures. The same letter notes that the General Duty Clause is not used to enforce consensus standards, but such standards are sometimes used as evidence of hazard recognition and of feasible ways to reduce the hazard.
The OSHA rules themselves sit in 29 CFR 1910, Subpart S (1910.301 through 1910.399) for general industry. OSHA's arc flash publication says OSHA standards follow NFPA 70E but that OSHA has never incorporated it by reference. It also reminds employers that the OSH Act's General Duty Clause requires a workplace free from recognized hazards likely to cause death or serious physical harm. In short, OSHA sets the obligation, and 70E is where most employers get the detail on how to meet it.
Why arc flash matters in commercial buildings
OSHA's guidance says arc flashes typically involve large electrical panels, motor control centers, switchboards, transformers, disconnects and metal-clad switchgear. That is the equipment in every commercial electrical room. Among the causes it lists are faulty equipment, inadequate installation or maintenance, unauthorized modifications, missing warning labels, and the assumption that equipment at 240 volts and under cannot produce an arc. It also names corrosion, loose contacts and moisture on insulating material as conditions that raise the likelihood. In coastal South Florida, salt air and humidity are working on your gear every day.
What arc flash labels are
An arc flash label is a warning on the equipment itself, telling a qualified person about the hazard before they open it. OSHA's interpretation letter is useful on this point. OSHA has no specific rule requiring arc flash marking. But 1910.303(e) requires equipment to carry its voltage, current and other ratings, and 1910.335(b) requires safety signs or tags to warn employees about electrical hazards, including arc flash. The letter quotes the NFPA 70E text of the time: switchboards, panelboards, industrial control panels and motor control centers in other than dwelling occupancies that are likely to be worked on while energized shall be field marked to warn of potential arc flash hazards.
A label produced from an engineering study goes further. It carries the results of the incident energy estimate. OSHA's guidance explains that this estimate determines the arc flash boundary, the incident energy at the working distance, and the level of protective equipment needed for any permitted energized work. That is why labels go stale. Change the utility transformer, the breaker settings or the conductors, and the numbers on the label may no longer be true.
What an arc flash risk assessment or study is
An arc flash study models the building's electrical system to estimate how much energy an arc could release at each piece of equipment. OSHA's guidance says conducting an arc flash study is highly recommended for all employers whose workers may be exposed to electrical hazards, not just utilities. It also notes that the different calculation methods can give very different results, and recommends using the most reasonable and conservative ones.
Who performs it
This is engineering work. Building owners should engage an electrical engineering firm to perform the study, produce the labels and make recommendations. An electrical contractor's role sits around the study, not inside it. That role is keeping the equipment in the condition the study assumes, and carrying out corrective work the engineer specifies.
What the engineer will ask you for
- A current one-line diagram of the electrical system, or the time and access to build one.
- Utility fault current data. FPL's Electric Service Standards say FPL will tell the customer the available short-circuit current on request.
- Equipment nameplates, breaker and fuse types, and protective device settings.
- Conductor sizes and lengths between major pieces of equipment.
What building owners can do
- Keep the one-line diagram current. Every tenant improvement, service change or new large load should update it. A study built on an old diagram describes a building that no longer exists.
- Maintain the protective devices. OSHA's guidance points out that if a breaker does not open as quickly as intended, the arc flash energy will be higher than expected. Poorly maintained equipment can also make the calculated values inaccurate. That is the case for preventive electrical maintenance: inspection, cleaning, torque checks and exercise of the equipment on a schedule.
- Label, and relabel after changes. Treat labels as part of the system, not a one-time sticker.
- Avoid energized work. OSHA's 1910.333(a)(1) requires live parts to be de-energized before an employee works on or near them, unless the employer can show that de-energizing creates additional hazards or is infeasible. "The store is open" is not on that list.
- Plan shutdowns so there is never pressure to work hot. Our guide to getting electrical work done without closing the business covers how outages are kept short.
- Keep electrical rooms clear. OSHA's working space rules require clear space in front of equipment likely to be serviced while energized. A storage room with a panel in it is a hazard.
- Control who opens the gear. Keep electrical rooms locked. Ask any contractor how they will create an electrically safe work condition, and how they handle energized work if it is truly unavoidable.
After a storm or a trip
South Florida's hurricane season adds one more rule. After a protective device trips, OSHA's 1910.334(b) says the circuit may not be manually re-energized until it has been determined that it can be safely energized, and it prohibits repetitive manual reclosing. For flooded or storm-damaged gear, get it inspected before anyone turns it back on.
Where your switchgear fits in
Most of a commercial building's arc flash exposure sits at the service and distribution equipment. If you are not sure what you have, our explainer on what switchgear is is a good start. When a study recommends replacing or upgrading service equipment, see commercial service and switchgear.
Next steps
Start with the basics you control: a current one-line diagram, a maintenance schedule for the service and distribution equipment, and a rule that nobody works energized in your building without a written justification. KRW Electric (Florida license EC13012832) maintains and upgrades commercial electrical systems across Miami-Dade, Broward and Palm Beach, and works alongside the engineering firm you choose for the study. See preventive maintenance, then send us the details, or call (305) 359-7312.
Reviewed by Kyle White, KRW Electric Company LLC — licensed electrical contractor EC13012832.
