Scaled Management Systems

Replacing chlorine gas

Replacing chlorine gas in public swimming pools


Water in public swimming pools is treated to prevent harmful bacteria. This is usually achieved by introducing gaseous chlorine through an induction system after the recirculated water from the pool has been filtered. Chlorine is a potentially harmful gas with a particularly irritating odour. Employees exposed to chlorine gas may experience chemical burns to the eyes and breathing problems. Prolonged exposure may result in hypoxia (the inability of oxygen to reach the body’s tissues).

Employees are particularly at risk of exposure during the transportation of chlorine gas cylinders, removing and fitting the cylinders from and to the induction system and general maintenance of the filtration equipment. Concentrated chlorine gas released in an enclosed space may result in an employee becoming unconscious and in extreme circumstances dying.


The employees working at a rural pool centre discussed the issue with their Manager and a review was undertaken of the chemicals used. After obtaining information on several chemicals the chlorine gas was replaced with liquid sodium hypochlorite which contains approximately 10% free chlorine. The substitution of the chemical required only minor changes to the existing induction system to convert it to use a liquid instead of chlorine gas.

Employees still come into contact with the chemical during the opening of the sodium hypochlorite containers and during the maintenance of the system. While performing these tasks the employees are required to wear personal protective equipment to minimise direct contact with the chemical.

Hierarchy of Controls:

Substitution & personal protective equipment (PPE)


  • Because chlorine gas was substituted with sodium hypochlorite the risk level of exposure has been significantly decreased.