Oxygen (O)

A colourless and odourless gaseous element that makes up 20.9% of the Earth’s atmosphere.

Oxygen is highly reactive and readily oxidises many materials at both ambient and elevated temperatures. Oxide films can sometimes be an advantage on metals, imparting corrosion resistance or a cosmetic finish to a component, so some heat treatment atmospheres contain oxygen-bearing constituents such as water vapour.

Oxygen is the only gas capable of supporting life and oxygen deficiency is a danger to life, especially in confined spaces. Symptoms or effects of reduced oxygen levels are:

20.9-18% oxygen	Normal breathing
18-14% oxygen	Breathing and pulse rate increased, muscular coordination slightly disturbed
14-10% oxygen	Emotional upset, abnormal fatigue, disturbed respiration
10-6% oxygen	Nausea and vomiting, collapse or loss of consciousness
Below 6% oxygen	Convulsions, respiratory collapse and rapid death

Properties:	Boiling Point:	-183.0ºC
	Relative density	1.1 (Air = 1)

Discovered in 1774 by Joseph Priestly and named from the Greek words oxus (acid) and gennan (forming). In its natural form it has two atoms combined: O2.

Ozone (O3) is another form of oxygen, containing three oxygen atoms combined together. It is formed naturally in the atmosphere by the action of ultraviolet light on oxygen and during electrical discharges. It is the acrid smell, noticeable after using a child’s electric train set for some time.

Oxygen (O)

A colourless and odourless gaseous element that makes up 20.9% of the Earth’s atmosphere.

Oxygen is the only gas capable of supporting life and oxygen deficiency is a danger to life, especially in confined spaces. Symptoms or effects of reduced oxygen levels are:

20.9-18% oxygen	Normal breathing
18-14% oxygen	Breathing and pulse rate increased, muscular coordination slightly disturbed
14-10% oxygen	Emotional upset, abnormal fatigue, disturbed respiration
10-6% oxygen	Nausea and vomiting, collapse or loss of consciousness
Below 6% oxygen	Convulsions, respiratory collapse and rapid death

Properties:	Boiling Point:	-183.0ºC
	Relative density	1.1 (Air = 1)

Discovered in 1774 by Joseph Priestly and named from the Greek words oxus (acid) and gennan (forming). In its natural form it has two atoms combined: O2.