What are compressed gases?
Thousands of products are available which contain gases and mixtures of gases stored under pressure in cylinders. Most of these gases are classified as “compressed gases” according to WHMIS technical criteria. The Controlled Products Regulations contain details of these criteria. What are the three major groups of compressed gases? There are three major groups of compressed gases stored in cylinders: liquefied, non-liquefied and dissolved gases. In each case, the pressure of the gas in the cylinder is commonly given in units of kilopascals (kPa) or pounds per square inch gauge (psig). Gauge pressure = Total gas pressure inside cylinder – atmospheric pressure Atmospheric pressure is normally about 101.4 kPa (14.7 psi). Note that compressed gas cylinder with a pressure gauge reading of 0 kPa or 0 psig is not really empty. It still contains gas at atmospheric pressure. Liquefied Gases Liquefied gases are gases which can become liquids at normal temperatures when they are inside cylinders
