Gases and pressurised devices

Gases are chemical substances and mixtures that are:

• completely gaseous at 20 °C, at a standard pressure of 101.3 kPa
• in a liquid state with a vapour pressure of more than 3 bar (300 kPa, absolute pressure) at 50 °C (condensed gas)
• carbon dioxide in a solid state

The state of aggregation of a substance (solid, liquid or gas) is determined by the substance's surroundings. When pressure and temperature change, the substance can change from one state to another. Handling of gas often takes place at high pressures, which places great demands on the material. Gases have various harmful effects on health. Some gases can irritate the mucous membranes of the eyes and respiratory tract, some have negative effects on the central nervous system, while others can have corrosive properties.

In premises where gas is handled, ventilation must be such that the oxygen concentration in the air normally does not fall below 20% by volume and does not exceed 22% by volume. If the oxygen concentration is below 18% by volume, breathing apparatus must be used when working in the premises. ORU has pressurized devices in the form of, for example, gas cylinders, fire extinguishers and autoclaves.