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SESK: Stuff Everyone Should Know · sesk.info/pilot-oxygen-no-oil-grease

Why must oil and grease be kept away from aircraft oxygen equipment?

They may ignite when exposed to oxygen.

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  1. They clog the oxygen mask
  2. They may ignite when exposed to oxygen ✔
  3. They lower the oxygen bottle pressure

Why: Materials that barely burn in normal air can burn readily in pure oxygen. The PHAK says oils and greases may ignite around oxygen, so they can't seal oxygen fittings, and smoking is banned while using oxygen.

Huh, didn't know that: Aircraft oxygen should meet the Aviator's Breathing Oxygen purity standard, SAE AS8010.

The dad joke
I tried to grease my oxygen bottle. It told me to stop being so slick.
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References

Answer: They may ignite when exposed to oxygen. Materials that barely burn in normal air can burn readily in pure oxygen. The PHAK says oils and greases may ignite around oxygen, so they can't seal oxygen fittings, and smoking is banned while using oxygen.

  1. Pilot's Handbook of Aeronautical Knowledge FAA-H-8083-25C, Chapter 7 www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/phak/09_phak_ch7.pdf
    Oils and greases may ignite if exposed to oxygen and cannot be used for sealing the valves and fittings of oxygen equipment.
    Checked 2026-10-09.

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