OSHA term · Glossary
Benzene
Verified vs OSHA sources · 2026-10-05
A colorless, sweet-smelling flammable liquid and a confirmed human carcinogen that causes leukemia and other blood disorders (including aplastic anemia). Benzene is found in crude oil, gasoline, and many industrial processes. OSHA regulates it under 29 CFR 1910.1028 with a permissible exposure limit of 1 ppm as an 8-hour TWA, a short-term exposure limit (STEL) of 5 ppm over any 15-minute period, and an action level of 0.5 ppm. Employers must establish regulated areas wherever exposures exceed the PEL or STEL.
Also known as: benzol, C6H6
On this page
Benzene at a glance
- PEL: 1 ppm as an 8-hour TWA (29 CFR 1910.1028(c)(1)).
- STEL: 5 ppm averaged over any 15-minute period (1910.1028(c)(2)).
- Action level: 0.5 ppm (8-hour TWA) — triggers monitoring and medical surveillance.
- Confirmed human carcinogen — causes acute myeloid leukemia (AML) and other blood/bone-marrow disorders.
- Medical surveillance required for exposure at/above the action level for 30+ days per year, or above the PEL/STEL for 10+ days per year.
- Regulated areas must be established wherever exposures exceed the PEL or STEL, with access limited to authorized personnel.
- Common sources: petroleum refining, gasoline, coke ovens, and manufacture of rubber, plastics, dyes, and detergents.
In plain English
A common petroleum chemical that causes leukemia — a cancer of the blood — even at low levels over time. It's in gasoline and many refinery and chemical processes. OSHA holds airborne benzene to 1 ppm over a shift and 5 ppm over any 15 minutes, and requires roped-off 'regulated areas' plus regular blood testing for exposed workers.
What the rule says
“The employer shall assure that no employee is exposed to an airborne concentration of benzene in excess of one part of benzene per million parts of air (1 ppm) as an 8-hour time-weighted average. … The employer shall assure that no employee is exposed to an airborne concentration of benzene in excess of five (5) ppm as averaged over any 15 minute period.”
In context
An enforcement, recordkeeping, or general-duty concept under the Occupational Safety and Health Act and 29 CFR. These terms define how OSHA inspects, cites, and penalizes employers.
Where this is written in OSHA's rules
- 29 CFR 1910.1028Read on eCFR / OSHA.gov
- 29 CFR 1910.1028(c)Read on eCFR / OSHA.gov
Example
A refinery technician's personal air sample reads 0.7 ppm benzene as an 8-hour TWA — above the 0.5 ppm action level but below the 1 ppm PEL. Because exposure exceeds the action level and occurs on more than 30 days a year, the employer must enroll the technician in medical surveillance, including a complete blood count to screen for early hematologic effects. If a valve-maintenance task briefly spikes exposure above 5 ppm over 15 minutes, that area becomes a regulated area requiring respiratory protection and restricted access.
Why it matters
Benzene is one of the most well-established occupational carcinogens, and its link to leukemia drove some of OSHA's most significant health rulemaking (the landmark 1980 'Benzene' Supreme Court decision shaped how OSHA must justify health standards). Because benzene causes cancer through cumulative exposure with no clear safe threshold, the low 1 ppm PEL, the STEL, and mandatory blood monitoring work together to catch both chronic and acute exposures before disease develops.
PEL vs. STEL vs. action level
Benzene is controlled by three different numbers that serve distinct purposes. The PEL (1 ppm) is the ceiling for average exposure across a full 8-hour shift. The STEL (5 ppm) caps short bursts — any 15-minute period — so a brief high exposure can violate the STEL even if the 8-hour average is fine. The action level (0.5 ppm), set below the PEL, is not a violation threshold at all — it is the trigger for monitoring and medical surveillance, catching problems before the PEL is breached. All three can apply to the same worker on the same day.
Benzene Exposure Limits (29 CFR 1910.1028)
| Limit | Value | Averaging Period / Role |
|---|---|---|
| PEL | 1 ppm | 8-hour TWA (enforceable ceiling) |
| STEL | 5 ppm | Any 15-minute period (short-term ceiling) |
| Action level | 0.5 ppm | 8-hour TWA (triggers monitoring + surveillance) |
Benzene: frequently asked questions
- What is the OSHA permissible exposure limit for benzene?
- Under 29 CFR 1910.1028, the benzene PEL is 1 ppm as an 8-hour time-weighted average, with a short-term exposure limit (STEL) of 5 ppm averaged over any 15-minute period. The action level is 0.5 ppm as an 8-hour TWA, which triggers exposure monitoring and medical surveillance obligations.
- What disease does benzene cause?
- Benzene is a confirmed human carcinogen that primarily causes acute myeloid leukemia (AML) and related blood and bone-marrow disorders, including aplastic anemia. Its effects are cumulative and can develop years after exposure. Because of this, OSHA requires medical surveillance — including complete blood counts — for workers exposed at or above the action level, to detect early hematologic changes.
- When must an employer set up a benzene regulated area?
- An employer must establish a regulated area wherever airborne benzene concentrations exceed, or can reasonably be expected to exceed, either the 1 ppm 8-hour TWA PEL or the 5 ppm 15-minute STEL. Regulated areas must be demarcated, separated from the rest of the workplace to limit exposure, and restricted to authorized personnel wearing appropriate respiratory protection.
Related terms
More OSHA terms
The action an employer takes to fix a cited violation or eliminate a hazard OSHA identified during an inspection. The citation sets an abatement date, the deadline to correct the hazard, and within 10 calendar days after that date the employer must certify to OSHA that the violation was abated. Failure to abate accrues additional penalties of up to $16,550 per day.
Area DirectorThe senior OSHA official in charge of a specific OSHA Area Office — the local unit that runs inspections and enforcement in its geographic territory. The Area Director has the authority to issue citations, propose penalties, hold informal conferences with employers, and approve settlement agreements. When a Compliance Safety and Health Officer (CSHO) completes an inspection, it's the Area Director who ultimately issues the citation.
Bureau of Labor Statistics (BLS)The federal statistical agency within the U.S. Department of Labor that collects, analyzes, and publishes data on workplace injuries, illnesses, and fatalities. BLS conducts the annual Survey of Occupational Injuries and Illnesses (SOII) — compiled from employer OSHA 300 logs — and the Census of Fatal Occupational Injuries (CFOI). SOII data drives OSHA's Site-Specific Targeting (SST) program: establishments whose DART rates significantly exceed their BLS industry average are placed on the SST inspection list.
Competent PersonUnder OSHA's construction standards, a person who is capable of identifying existing and predictable hazards in the surroundings or working conditions, and who has the authorization to take prompt corrective measures to eliminate them. The role requires both knowledge and the authority to act, and is mandated by name in many specific standards — excavations, scaffolds, fall protection, asbestos, and more.
CitationThe formal written notice OSHA issues to an employer after an inspection, describing each alleged violation, the standard cited, the proposed penalty, and the date by which the hazard must be corrected (abated). OSHA must issue a citation with reasonable promptness and no later than six months after the violation occurred.
Closing ConferenceThe meeting at the end of an OSHA inspection where the compliance officer confers with the employer and informally advises them of any apparent violations found. Importantly, the closing conference discusses what was observed and the employer's rights — but it does NOT state final citations or penalties, which come later in the written Citation and Notification of Penalty.
Compliance Officer (CSHO)An OSHA Compliance Safety and Health Officer — the inspector who conducts workplace inspections. A CSHO presents credentials (a photo ID and a serial number), holds the opening conference, performs the walkaround, collects evidence, interviews employees, and recommends citations. CSHOs are either safety specialists or industrial hygienists.
ContestAn employer's formal challenge to an OSHA citation, penalty, or abatement date. To contest, the employer must file a written Notice of Contest with the OSHA Area Director within 15 working days of receiving the Citation and Notification of Penalty. Filing sends the case to the independent Occupational Safety and Health Review Commission (OSHRC); missing the deadline makes the citation a final, un-appealable order.
Sources & verification
- 29 CFR 1910.1028 (eCFR / OSHA.gov)
- 29 CFR 1910.1028(c) (eCFR / OSHA.gov)
- OSHA — Benzene (Safety and Health Topics)
- OSHA — 29 CFR 1910.1028 (Benzene)
Reviewed by HazComFast against eCFR, OSHA.gov, NIOSH, and the Federal Register. Last reviewed 2026-10-05. This glossary is general information, not legal advice; OSHA State-Plan states (e.g. California, Michigan) may adopt stricter requirements.
Put Benzene into practice
Don't just read the definition — get compliant. Explore HazComFast's free OSHA & HazCom tools to apply Benzene on your jobsite.
Get the Binder in Order Before the Inspector Arrives. Are You Ready?
OSHA does not give advance notice of inspections (29 CFR 1903.6). Get the binder in order before the opening conference, not during it.
Serious Violation
$16,550
per violation (max)
HazComFast Pro
$199/mo
10 jobsites, unlimited chemicals, unlimited workers
New sign-ups are paused. The free tools below need no account, and customers can log in as usual.
Your account keeps working as usual. Cancel anytime.