Air that is continually kept under a certain pressure is known as Compressed Air, the pressure that it is kept at is more than often higher than that of the earth's atmosphere.
It is a fact that around 10% of electricity that is used around Europe is used by compressed air equipment to keep air compressed, that energy that is used adds per year up to 80 terawatt hours.
This equipment can cause certain hazards (dangers) like blasts under 40 psi from this equipment from close range can easily rupture an eardrum and in some extreme cases has the potential to cause brain damage, if for some reason the blast becomes directed to the mouth then this can cause a person's lungs to rupture.
It is extremely important that these machines are used with due care and in controlled environments.
Compressed Air Equipment has many uses, some of which are: Pneumatics - These are used on machinery for work and engineering.
Scuba Diving - This type of air is essential to inflate safety devices and buoyancy equipment; the breath gas cylinders carried by the diver also require pressurised air to work.
Gas Dusters - Some components you come across will not be possible to clean with the use of water, gas duster are an alternative.
Air Brakes - Automotive garages will use this equipment in the process of setting up air brakes.
There are many reasons for commercial companies needing this equipment, it all depends on the type of industry they are in, be sure to look around and read up on the products you are buying.