Investigation of poor
indoor air quality

The problem

Staff in a government office in NT reported poor indoor air quality and odours over many years.

A quick examination of the mechanical systems and mechanical room identified a drain line from several air conditioners running through the fan room and emptying into a funnel-shaped drain. This drain had a trap to prevent air movement of sewer gases into the mechanical room, but upon examination, the trap was dry and no longer functioning as a block to air flow.

Unfortunately, the mechanical room where this was present was part of the return airflow, and subject to the suck of a large fan, and therefore was sucking sewer gases into the fan room, where they were distributed to the occupied areas, resulting in the air quality complaints.

The outcome

Replacing the opaque plastic “U” trap with a clear acrylic trap and ensuring that the trap stayed filled with water rectified the problem.