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SESK: Stuff Everyone Should Know · sesk.info/osha-confined-space-testing

When testing the air in a permit space, what must you test for first?

Oxygen, then combustible gases, then toxic gases.

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  1. Oxygen ✔
  2. Toxic gases
  3. Combustible gases

Why: OSHA sets the order: test first for oxygen, then combustible gases and vapors, then toxic gases and vapors. Testing must show acceptable conditions before entry is allowed.

Huh, didn't know that: Entrants have the right to watch the pre-entry testing.

The dad joke
Why did the air tester get promoted? It always passed the sniff test.
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References

Answer: Oxygen. OSHA sets the order: test first for oxygen, then combustible gases and vapors, then toxic gases and vapors. Testing must show acceptable conditions before entry is allowed.

  1. 29 CFR 1910.146 Permit-required confined spaces www.ecfr.gov/current/title-29/subtitle-B/chapter-XVII/part-1910/subpart-J/section-1910.146
    test first for oxygen, then for combustible gases and vapors, and then for toxic gases and vapors
    Checked 2026-10-10.

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