Air is composed of four elements, along with greenhouse gases. These are: Nitrogen, Oxygen, Argon and Carbon dioxide
Nitrogen is a gas, making up 78% of the air. It is odourless and colourless. Nitrogen is used to make fertilisers, nitric acid, nylon, dyes and explosives. These must be reacted with hydrogen to make ammonia, which is used in cleaning products.
Oxygen is the second most abundant gas found in air. Oxygen is a reactive, nonmetal gas that is most reactive with metals such as iron; making iron oxide. Oxygen is the prime gas we breath, and is essential to our bodies. It passes through our blood, into the heart and around the body. Without it, we would be nonexistent.
Argon is also found in air, but only in small proportions. Argon is the most abundant gas in the earths crust, composing 0.00015% of it. It is used in some metal arc welding and in the procession of titanium and other reactive metals.
Carbon dioxide is the scarcest of the four gases in air. Carbon dioxide is a greenhouse gas, reactive and odourless. It is used in dry ice, fire extinguishers and carbonated soft drinks. It is safe in small amounts only.