Bottled gas

Bottled gas is a term used for substances which are gaseous at standard temperature and pressure (STP) and have been compressed and stored in carbon steel, stainless steel, aluminum, or composite bottles known as gas cylinders. Bottled gas is a term used for substances which are gaseous at standard temperature and pressure (STP) and have been compressed and stored in carbon steel, stainless steel, aluminum, or composite bottles known as gas cylinders. There are four cases: either the substance remains a gas at standard temperature but increased pressure, the substance liquefies at standard temperature but increased pressure, the substance is dissolved in a solvent, or the substance is liquefied at reduced temperature and increased pressure. In the last case the bottle is constructed with an inner and outer shell separated by a vacuum (dewar flask) so that the low temperature can be maintained by evaporative cooling. The substance remains a gas at standard temperature and increased pressure, its critical temperature being below standard temperature. Examples include: The substance liquefies at standard temperature but increased pressure. Examples include: The substance is dissolved at standard temperature in a solvent. Examples include: The substance is liquefied at reduced temperature and increased pressure. These are also referred to as cryogenic gases. Examples include: The general rule is that one unit volume of liquid will expand to approximately 800 unit volumes of gas at Standard temperature and pressure with some variation due to intermolecular force and molecule size compared to an ideal gas. Normal high pressure gas cylinders or bottles will hold from 200 to 400 atmosphere (unit)s. The atmosphere units pressure held by the bottle is equivalent to the number of volumes of standard temperature and pressure of the gas held by the bottle for an ideal gas. Because the contents are under high pressure and are sometimes hazardous, there are special safety regulations for handling bottled gases. These include chaining bottles to prevent falling and breaking, proper ventilation to prevent injury or death in case of leaks and signage to indicate the potential hazards. In the United States, the Compressed Gas Association (CGA) sells a number of booklets and pamphlets on safe handling and use of bottled gases. (Members of the CGA can get the pamphlets for free.) The European Industrial Gases Association and the British Compressed Gases Association provide similar facilities in Europe and the United Kingdom.