1910.146(d)(5)(iii): Order of Atmospheric Testing
When testing a permit space for atmospheric hazards, test first for oxygen, then for combustible gases and vapors, and then for toxic gases and vapors.
Key takeaways
- 1910.146(d)(5)(iii) is part of OSHA's general industry standards (29 CFR Part 1910, Subpart J).
- OSHA cited it 4 times in the last 3 years, in 4 inspections, with $8,000 in current penalties.
- 1 death is linked to inspections that cited this rule.
- Related part: 1910.146(d) Permit-required confined space program (480 citations).
- Free 5-minute toolbox talk for your crew below.
In this article
What this rule covers
29 CFR 1910.146(d)(5)(iii) is one requirement inside 1910.146 Permit-required confined spaces, an OSHA general industry standard (Part 1910, Subpart J). The official text below is copied word for word from the Electronic Code of Federal Regulations (eCFR). The numbers, injury cases and training on this page show how OSHA enforces it on real job sites.
Official text
(iii) When testing for atmospheric hazards, test first for oxygen, then for combustible gases and vapors, and then for toxic gases and vapors. 4 citations
Source: eCFR, text current as of 2026-10-15. Read all of 1910.146.
Injuries linked to this rule
1 death is linked to inspections where OSHA cited 1910.146(d)(5)(iii).
At 3:22 p.m. on May 29, 2024, Employee #1 was attempting to rescue a fellow employee who had been overcome by hydrogen sulfide (H2S) gas in an underground pump house. Prior to this incident, multiple coworkers had been working in the pump house and were…
Where and how often it was cited
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OSHA interpretation letters
Related parts of this rule
- 1910.146(d) Permit-required confined space program 480 citations
- 1910.146(d)(3) 107 citations
- 1910.146(d)(5) 91 citations
- 1910.146(d)(4) 66 citations
- 1910.146(d)(9) 63 citations
- 1910.146(d)(5)(i) 58 citations
- 1910.146(d)(2) 40 citations
- 1910.146(d)(4)(i) 33 citations
- 1910.146(d)(6) 31 citations
- 1910.146(d)(14) 23 citations
- 1910.146(d)(10) 17 citations
- 1910.146(d)(1) 16 citations
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Frequently asked questions
What is tested first in a confined space?
Oxygen.
What comes second?
Combustible gases and vapors.
What is tested last?
Toxic gases and vapors.
About this page
Sources
- 29 CFR 1910.146 (eCFR), text current as of 2026-10-15
- U.S. Department of Labor enforcement data: OSHA inspections, citations and accident records, copied nightly; data as of 2026-10-20
3-year window. Federal OSHA only; state-plan rules are not counted. Plain-language text is a summary, not legal advice; the official text controls. Black Belt Safety is not part of OSHA or the Department of Labor.