The university project for next year (2006/2007) will involve inflating air bags and regulating their pressure, to do this I will need a source of air or a similar gas namely Nitrogen; to do this I have opened an account with BOC one of the main compressed gas supply companies and found a very local distributor.

Compressed Gas comes in various different canisters from small 50cm high tanks up to tanks almost head height. For safety they come with different threads, this prevents potentially lethal mix-ups, the tank pressure depends on the gas involved for example Carbon Dioxide CO2 has a tank pressure of 50 Bar where as Nitrogen is pressurized to 200-300 Bar.
A regulator is used to lower the pressure, these fit to the tank and usually have different pressure gauges on one for the tank pressure and one for the output or line pressure. Regulators tend to limit the output pressure to a maximum of about 10 Bar although this varies with gas and regulator.

Below you can see the first tank I collected, this is a compressed air tank pressurised to 200 Bar.

BOC Air tank

The top has a built in valve this is controlled by a square stem valve wrench (as Air Products call it) or a Cylinder Key (as BOC call it).
This valve is only opened when a suitable regulator has been firmly attached.

BOC Air tank top