Oxygen (O2, LOX)

Oxygen is the most abundant element on the earth’s surface. It is the colorless, odorless, tasteless gas that supports life and makes combustion possible. It constitutes about one-fifth of the earth’s atmosphere (20.99 percent by volume). It is a transparent, pale blue liquid slightly heavier than water at temperatures ranging below approximately -300° F. All elements except the inert gases combine with oxygen, usually to form oxides. Oxygen purity is vital to efficient production. For example, 99.5 percent pure oxygen can produce high-quality, flame-cut edges. A drop of one percent in oxygen purity slows cutting speed 25 percent. At 95 percent oxygen purity, an oxy-fuel cutting torch will not cut steel at all.

Cylinder oxygen is produced from vaporized liquid oxygen. Its minimum guaranteed purity is 99.5 percent. Liquid oxygen is classified as Type II by the Compressed Gas Association (CGA). CGA Pamphlet G-4.3 Type II, Grade B and the United States Pharmacopia (USP) specifications are considered standards for “commercial” liquid oxygen. A variety of other CGA oxygen Grades are available on special order. Tese range from CGA Grade C, also 99.5 percent oxygen content to CGA Grade H (99.995 percent oxygen). Also available is high purity ULSI grade and ultra high purity VLSI grade (99.9999 percent pure) liquid oxygen for customers requiring stringent purity standards.


Oxygen makes it much easier for materials to ignite. Even materials that would not normally burn, like steel wool, will burn in an oxygen atmosphere. Only equipment “cleaned for Oxygen service” should be used for gaseous or liquid oxygen. Never use oil or organic lubricants on oxygen valves and regulators. Pure oxygen reacts about five times faster than air in oxidizing organic materials. Spontaneous combustion is likely to occur.

Care is necessary in housekeeping and product handling so as not to allow oxygen to contact organic materials or any flammable materials. Paints, thinners, and cleaning solvents also must be kept away from oxygen exposures and no ignition sources should be allowed in areas where oxygen is stored or used. No smoking is allowed in areas where oxygen is used and stored.

Use clean gloves or hands washed free of any oils or grease when handling oxygen equipment. Liquid oxygen is very cold and causes cryogenic “burns”. The eyes and lungs are especially sensitive to the cold vapors. Protect eyes and skin from exposure to low temperature materials with safety goggles, loose fitting gloves and protective clothing.

Oxygen is nontoxic, but high concentrations may damage the respiratory tract over time.

Clothing which has absorbed liquid oxygen or oxygen gas must be removed and aired out for at least 30 minutes before it is considered safe to wear.

Oxygen Weight Gas Liquid
PoundsLb KilogramsKg Cubic FeetSCF Cubic MetersNm3 GallonsGal LitersL
  1 Pound 1.0 0.4536 12.076 0.3174 0.1050 0.3977
  1 Kilogram 2.205 1.0 26.62 0.6998 0.2316 0.8767
  1 SCF Gas 0.08281 0.03756 1.0 0.02628 0.008691 0.0329
  1 Nm3 Gas 3.151 1.4291 38.04 1.0 0.3310 1.2528
  1 Gal Liquid 9.527 4.322 115.1 3.025 1.0 3.785
  1 L Liquid 2.517 1.1417 30.38 0.7983 0.2642 1.0