Oxygen cylinder: High-pressure tank storing medical O2 at 2000 psi.
Key specs: Sizes D, E, M, H. E-size = 660L, lasts ∼2-5 hrs at 2LPM. Color-coded white.
Use: Emergency backup, ambulance, home O2. Needs regulator + flowmeter.
Safety: Store upright, away from heat/oil. Check expiry + hydro test date.