Good indoor air quality (IAQ) is desired for a healthy indoor environment. Poor indoor air quality can cause a variety of health problems ranging from temporary to long term. Health problems commonly associated with poor IAQ include allergic reactions, respiratory problems, eye irritation, sinusitis, bronchitis and pneumonia.

IAQ problems arise in non-industrial buildings (an indoor or enclosed work space that is served by a ventilating and air conditioning system where there are person at work, but does not include premises that are used primarily as manufacturing and production facilities and vehicles) when there is an inadequate quantity of ventilation air being provided for the amount of air contaminants present in that space. Hence, IAQ and mechanical ventilating and air-conditioning systems (MVAC) are closely relate.

Agents derived from or that are living organisms (e.g. viruses, bacteria, fungi, and mammal and bird antigen) that can inhaled and can cause many types of health effects including allergic reactions, respiratory disorders, hypersensitivity diseases, and infectious diseases.

Compounds that evaporate from the many housekeeping, maintenance, and building products made with organic chemicals. These compounds are released from products that are being used and that are in storage. In sufficient quantities, VOCs can cause eye, nose and throat irritations,
headaches, dizziness, visual disorder, memory impairment; some are known to cause cancer in animals; some are known to cause cancer in humans.

In 2010, the Department has introduced the Industry Code of Practice on Indoor Air Quality 2010 to increase the compliance of designated workplaces. Activities regarding the issues of indoor air quality involve the investigation of complaints from workers. The procedure of handling any complaints can be found in the Industry Code of Practice on Indoor Air Quality (IAQ) 2010. Investigation usually involves five main activities, which are the preliminary site visit, measuring the level of contaminant in the area, data analysis, discussions with employers and the report writing.