Is arc flash covered by an OSHA standard?

Not by a single one. OSHA requires electrical PPE under 29 CFR 1910.335 (general industry) and 1926 Subpart K (construction), and codifies arc-flash protection for electric power generation, transmission, and distribution work at 1910.269(l)(8). For most other work, OSHA has no arc-flash-specific rule and enforces the recognized industry method — NFPA 70E — through the General Duty Clause and the PPE hazard-assessment duty (1910.132).

What is the arc-flash boundary?

The arc-flash boundary is the distance from an exposed energized part at which the incident energy equals 1.2 cal/cm² — the level that produces a second-degree burn on bare skin. Anyone inside that boundary must wear arc-rated PPE rated for the incident energy at their working distance (NFPA 70E).

What is the difference between arc flash and arc blast?

Arc flash is the thermal and light energy of the arc — the burn hazard. Arc blast is the explosive pressure wave, hot gases, and molten-metal shrapnel thrown by the same event — the concussion and projectile hazard. A single arc-fault event usually produces both.

How hot is an arc flash?

An electric arc can exceed 35,000°F — nearly four times the temperature of the surface of the sun (OSHA). At that temperature it vaporizes copper and other metals almost instantly, which is what drives the arc blast's pressure wave and shrapnel.

General safety term · Glossary

Arc Flash

Verified vs OSHA sources · 2026-10-05

An arc flash is the sudden release of thermal energy from an electrical arc fault — a short circuit that jumps through the air between energized parts. The arc can reach temperatures over 35,000°F (nearly four times the surface of the sun), causing severe burns, igniting clothing, and driving an explosive pressure wave known as the arc blast. OSHA sets no single “arc-flash standard”: the analysis method — the arc-flash boundary, incident energy, and arc-rated PPE — comes from the NFPA 70E consensus standard, which OSHA enforces through its electrical-PPE rules (29 CFR 1910.335, 1910.269) and the General Duty Clause.

29 CFR 1910.335(a)(1)(v)29 CFR 1910.335

Also known as: arc blast, electric arc-flash, flashover

Arc Flash at a glance

An electric arc can exceed 35,000°F — nearly four times the temperature of the sun's surface (OSHA).
The arc-flash boundary is the distance at which the incident energy reaches 1.2 cal/cm² — the onset of a second-degree burn on bare skin (NFPA 70E).
There is no single OSHA “arc-flash standard”: OSHA enforces electrical PPE under 29 CFR 1910.335 and 1926 Subpart K, arc-flash protection for power work under 1910.269(l)(8), and otherwise cites NFPA 70E through the General Duty Clause.
Arc-rated (AR) clothing must carry an arc rating (ATPV or EBT, in cal/cm²) at least equal to the calculated incident energy at the working distance.
OSHA cites arc-flash injuries under 1910.335 and the General Duty Clause — a 2024 case cited a manufacturer after a maintenance electrician suffered severe burns from an electrical arc.

PPE Category 1
4 cal/cm² (minimum arc rating)

PPE Category 2
8 cal/cm² (minimum arc rating)

PPE Category 3
25 cal/cm² (minimum arc rating)

PPE Category 4
40 cal/cm² (minimum arc rating)

Scale: 0–40 cal/cm² (minimum arc rating) (respirable crystalline silica, 8-hour TWA)

In plain English

A violent electrical explosion. When electricity jumps across a gap — from a dropped tool, a loose connection, or dust and moisture — it creates an arc hotter than the sun that can burn a worker severely from feet away, without any contact. The defense is de-energizing first, and, when live work is truly unavoidable, wearing clothing rated to survive the heat.

What the rule says

“Employees shall wear protective equipment for the eyes or face wherever there is danger of injury to the eyes or face from electric arcs or flashes or from flying objects resulting from electrical explosion.”
29 CFR 1910.335(a)(1)(v)

In context

An industrial-hygiene, exposure-control, or program-management concept that applies across OSHA standards and workplaces.

29 CFR 1910 / 1926

Where this is written in OSHA's rules

29 CFR 1910.335(a)(1)(v)Read on eCFR / OSHA.gov
29 CFR 1910.335Read on eCFR / OSHA.gov

Read the related guide

Example

A panel with a calculated incident energy of 8 cal/cm² at an 18-inch working distance requires arc-rated PPE with an arc rating of at least 8 cal/cm² (NFPA 70E PPE Category 2). A worker in ordinary cotton coveralls at that panel would face second-degree burns well past the 1.2 cal/cm² threshold — and untreated fabric can ignite and keep burning.

Why it matters

Arc flash is one of the deadliest electrical hazards precisely because the worker never has to touch anything — the heat, the pressure wave, and the molten-metal shrapnel reach out. Because OSHA has no single arc-flash rule, employers often assume it isn't regulated; in fact OSHA cites arc-flash burns under 29 CFR 1910.335 and the General Duty Clause, using NFPA 70E as the recognized method, and a 2024 enforcement case fined a manufacturer after an electrician was severely burned by an arc.

History & background

Arc-flash burns were recognized long before they could be quantified. Ralph Lee's 1982 paper “The Other Electrical Hazard: Electric Arc Blast Burns” gave engineers a way to calculate the burn threshold, and NFPA — which had published the first edition of NFPA 70E in 1979 at OSHA's request — built the arc-flash boundary and incident-energy analysis into later editions. OSHA added explicit arc-flash and incident-energy protection to the power-work standard at 29 CFR 1910.269(l)(8) in its 2014 final rule.

Arc flash vs. arc blast — and vs. shock

The arc FLASH is the intense thermal and light energy (the burn hazard). The arc BLAST is the pressure wave, superheated gases, and vaporized-metal shrapnel that accompany it (the concussion and projectile hazard). Both differ from electric SHOCK, which requires actual contact with an energized part. The arc-flash boundary guards against burns; the shock approach boundaries (limited and restricted) guard against contact — they are calculated differently and rarely coincide.

Arc-flash boundary vs. the shock approach boundaries (NFPA 70E)

Boundary	Hazard it addresses	What it means
Arc-flash boundary	Thermal — burns	Distance where incident energy = 1.2 cal/cm² (second-degree-burn onset); arc-rated PPE required inside it
Limited approach	Shock — contact	Unqualified persons kept outside unless escorted by a qualified person
Restricted approach	Shock — increased contact risk	Only qualified persons, with shock PPE and a documented plan, may cross

Arc Flash: frequently asked questions

Is arc flash covered by an OSHA standard?: Not by a single one. OSHA requires electrical PPE under 29 CFR 1910.335 (general industry) and 1926 Subpart K (construction), and codifies arc-flash protection for electric power generation, transmission, and distribution work at 1910.269(l)(8). For most other work, OSHA has no arc-flash-specific rule and enforces the recognized industry method — NFPA 70E — through the General Duty Clause and the PPE hazard-assessment duty (1910.132).
What is the arc-flash boundary?: The arc-flash boundary is the distance from an exposed energized part at which the incident energy equals 1.2 cal/cm² — the level that produces a second-degree burn on bare skin. Anyone inside that boundary must wear arc-rated PPE rated for the incident energy at their working distance (NFPA 70E).
What is the difference between arc flash and arc blast?: Arc flash is the thermal and light energy of the arc — the burn hazard. Arc blast is the explosive pressure wave, hot gases, and molten-metal shrapnel thrown by the same event — the concussion and projectile hazard. A single arc-fault event usually produces both.
How hot is an arc flash?: An electric arc can exceed 35,000°F — nearly four times the temperature of the surface of the sun (OSHA). At that temperature it vaporizes copper and other metals almost instantly, which is what drives the arc blast's pressure wave and shrapnel.

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More General Safety terms

Action Level

An airborne concentration of a substance — typically half the PEL — at which certain provisions of an OSHA standard kick in (such as exposure monitoring, training, and medical surveillance), even though it is below the legal exposure limit. For respirable crystalline silica the action level is 25 µg/m³ as an 8-hour TWA, half the 50 µg/m³ PEL.

Administrative Controls

Changes to how and when work is done — job rotation, scheduling, safe work practices, housekeeping, training, and signage — that reduce a worker's exposure without altering the hazard itself. They are the fourth tier of the hierarchy of controls, below engineering controls and above PPE.

Biological Exposure Index (BEI)

An ACGIH guidance value for interpreting biological monitoring results — the concentration of a chemical (or its metabolite) measured in a worker's blood, urine, or exhaled breath. A BEI represents the level most likely found in a healthy worker whose inhalation exposure was at the TLV, so it measures the dose the body actually absorbed, not just what's in the air.

California Proposition 65

California's Safe Drinking Water and Toxic Enforcement Act of 1986. It requires businesses to warn Californians before exposing them to any of the ~900+ listed chemicals known to the state to cause cancer, birth defects, or other reproductive harm, and prohibits discharging those chemicals into drinking-water sources. It's a California law, but it reaches nearly any product sold there.

CAS Number

A unique numerical identifier assigned by the Chemical Abstracts Service (a division of the American Chemical Society) to every distinct chemical substance. It has the format of up to seven digits, a dash, two digits, a dash, and a final check digit (e.g., 67-64-1 for acetone). Because chemical names vary, the CAS number is the unambiguous global key used on SDSs, inventories, and regulations.

Ceiling Limit

An exposure limit that must not be exceeded at any instant during the workday — the strictest type of OSHA exposure limit. In OSHA's Z-tables it is marked with a “C” before the value. Unlike an 8-hour TWA (an average) or a 15-minute STEL, a ceiling applies to a single moment.

Chemical Compatibility

Whether two or more chemicals can be safely stored or used near each other without reacting dangerously — releasing heat, toxic gas, or fire. Incompatible chemicals must be physically separated (segregated) in storage. Each chemical's incompatibilities are listed in Section 10 of its SDS, and compatibility drives storage layout and spill response.

Chemical Inventory

A list of the hazardous chemicals known to be present in a workplace, identified in a way that cross-references each chemical's safety data sheet. It's a required part of OSHA's written HazCom program (29 CFR 1910.1200(e)(1)(i)) and the foundation for SDS management, EPCRA Tier II reporting, and emergency planning.

Sources & verification

Reviewed by HazComFast against eCFR, OSHA.gov, NIOSH, and the Federal Register. Last reviewed 2026-07-23. This glossary is general information, not legal advice; OSHA State-Plan states (e.g. California, Michigan) may adopt stricter requirements.

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