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General regulatory information for lab, clinic and sterile-processing staff; it is not medical advice and not a substitute for the standard itself.
Short answer
OSHA’s ethylene oxide standard, 29 CFR 1910.1047, limits employee exposure to 1 part per million (ppm) as an 8-hour time-weighted average, with a 5 ppm excursion limit averaged over 15 minutes and an action level of 0.5 ppm (8-hour average) that starts monitoring and medical surveillance duties. NIOSH recommends a much lower exposure level, below 0.1 ppm.
Definition and scope
Ethylene oxide (EtO, CAS 75-21-8) is a flammable, highly reactive gas. OSHA’s EtO topic page lists three main uses: an intermediate for industrial chemicals (especially ethylene glycol), a fumigant for some agricultural products, and a sterilant for medical equipment and supplies. For labs and clinics the third use is the relevant one, because sterilizer rooms and aeration areas are where employees can be exposed.
The OSHA ethylene oxide standard (29 CFR 1910.1047, checked 2026-10-30) states in paragraph (a)(1) that it “applies to all occupational exposures to ethylene oxide.” Paragraph (a)(2) lists exceptions, including some products that contain EtO, so check the exception text before assuming a particular task is in or out. This page covers the occupational limits only; for how EtO compares with other sterilization methods see low-temperature sterilization method selection and sterilization technology.
How the OSHA limits are used in practice
The three numbers
- Permissible exposure limit (PEL): 1 ppm of airborne EtO as an 8-hour time-weighted average (paragraph (c)(1)).
- Excursion limit: 5 ppm averaged over 15 minutes (paragraph (c)(2)).
- Action level: 0.5 ppm calculated as an 8-hour time-weighted average (paragraph (b)).
Which reading triggers what
The table summarizes the cited paragraphs of 1910.1047 (checked 2026-10-30).
| Employee exposure result | What the standard requires | Paragraph |
|---|---|---|
| At or above 0.5 ppm (action level), at or below 1 ppm (8-hour average) | Repeat monitoring at least every 6 months | (d)(3)(i) |
| Above 1 ppm (8-hour average) | Repeat monitoring at least every 3 months | (d)(3)(ii) |
| Above the 5 ppm 15-minute excursion limit | Repeat monitoring at least every 3 months | (d)(3)(iv) |
| Anywhere exposure may exceed the 8-hour limit or the excursion limit | Employer establishes a regulated area | (e)(1) |
| Exposed at or above the action level for at least 30 days a year | Medical surveillance program for the employees concerned | (i)(1)(i)(A) |
The last row is one trigger; paragraph (i) contains further conditions, including medical examinations and consultations for employees exposed in an emergency, so read the full paragraph when planning a program.
Types and related concepts: OSHA, NIOSH and ACGIH values side by side
The OSHA ethylene oxide limits are not the only published numbers. Other bodies publish different values, and only the OSHA standard sets duties for employers. The NIOSH values below come from the NIOSH IDLH page for ethylene oxide (checked 2026-10-30).
| Source | Value for EtO | Type |
|---|---|---|
| OSHA 29 CFR 1910.1047 | 1 ppm 8-hour TWA; 5 ppm 15-minute excursion; 0.5 ppm action level | Regulatory standard for employers |
| NIOSH | REL below 0.1 ppm (below 0.18 mg/m³) TWA; 5 ppm (9 mg/m³) ceiling for 10 minutes per day | Recommended exposure limit |
| NIOSH | IDLH 800 ppm | Immediately dangerous to life or health concentration |
| ACGIH | TLV 1 ppm, listed A2 | Guideline value, as listed on the NIOSH page |
The NIOSH REL is below one tenth of the OSHA PEL. NIOSH describes EtO as a potential occupational carcinogen. For how PELs, RELs and TLVs differ in general, see PELs, TLVs and RELs in the laboratory.
Where it matters for labs, clinics and supply decisions
Because OSHA identifies EtO as a sterilant for medical equipment and supplies, any facility that runs an EtO sterilizer, or handles items directly from one, should know which result band its air-monitoring data falls into. The table above shows the practical consequence: results between 0.5 and 1 ppm still carry a six-month monitoring cycle, and 30 days a year at or above the action level brings in medical surveillance, even though the 1 ppm limit has not been exceeded.
OSHA’s topic page also links its Small Business Guide for Ethylene Oxide (Publication 3359, April 2009), which emphasizes air monitoring, and a hospitals eTool. For respiratory protection programs generally see respiratory protection program for laboratories. A comparable action-level structure for another regulated chemical is described in formaldehyde PEL, STEL and action level monitoring.
Common misunderstandings
- “1 ppm is the only number.” The standard also sets a 5 ppm 15-minute excursion limit and a 0.5 ppm action level, and each has its own consequence.
- “Below the PEL means no duties.” At or above the action level, monitoring repeats at least every 6 months, and the medical surveillance trigger is tied to the action level, not the PEL.
- “The NIOSH number is the legal limit.” The NIOSH value is a recommended exposure limit; the OSHA standard is what binds employers.
- “The standard covers every EtO-containing product.” Paragraph (a)(2) lists exceptions; read it for the product in question.
FAQ
What is the OSHA limit for ethylene oxide?
1 ppm as an 8-hour time-weighted average, plus a 5 ppm excursion limit averaged over 15 minutes, under 29 CFR 1910.1047(c).
What is the action level for ethylene oxide?
0.5 ppm calculated as an 8-hour time-weighted average, per 1910.1047(b).
How often must EtO exposure be monitored?
At least every 6 months when results are at or above the action level and at or below the 8-hour limit; at least every 3 months above the 8-hour limit or above the excursion limit (paragraph (d)(3)).
Is the NIOSH recommended level the same as the OSHA limit?
No. NIOSH lists a REL below 0.1 ppm as an 8-hour TWA and treats EtO as a potential occupational carcinogen; OSHA’s PEL is 1 ppm.
Sources
- OSHA, 29 CFR 1910.1047, Ethylene oxide, checked 2026-10-30.
- CDC NIOSH, Ethylene oxide, IDLH and REL values, checked 2026-10-30.
- OSHA, Ethylene oxide topic page, checked 2026-10-30.
