Non-flammable gas that can present a hazard

Sulphur dioxide

Sulphur dioxide is a colourless, irritant and corrosive gas with an irritating pungent odour. Sulphur dioxide is heavier than air. In the event of leakage, it evaporates generating a mist of sulphuric acid.

This gas has a corrosive effect on most metals, especially at high humidity, and damages textiles and leather. It can react violently with alkalis. Liquid sulphur dioxide also corrodes plastics and rubber.

Sulphur dioxide is not flammable or explosive. However, when diluted with water, sulphur dioxide can react with metals to form flammable hydrogen. Like other gases stored under pressure, sulphur dioxide cylinders must be handled with care and the cylinders can explode when heated. Cylinders are to be stored locked up in well ventilated areas at temperatures of under 50 °C. The cylinders are grey with a yellow top.

Sulphur dioxide irritates the eyes and airways, leading to eye watering and coughing. Sulphur dioxide can cause corrosive damage, especially on damp areas of skin. The gas is lethal to inhale at high concentrations (about 400 ppm).