Indoor environmental quality (IEQ) refers to the environmental quality within a building, focusing specifically on the health and comfort of the occupants. This generally includes air quality, thermal comfort, artificial lighting and day lighting.

The CSIR’s Llewellyn van Wyk gives some pointers on IEQ:
Green building rating tools emphasise the importance of paying attention to indoor air quality (IAQ) throughout the design and construction of buildings. One of the markers for acceptable levels of IAQ is the frequency of effective turnover of interior air by replacement with outside air.

One of the strategies used to reduce energy consumption while maintaining adequate air quality is demand-controlled ventilation. This system uses carbon dioxide sensors to control the rate, based on the emissions of people in the building.

IAQ may be affected negatively by microbial contaminants such as mould or bacteria; chemicals such as carbon monoxide and radon; allergens; and any other mass or energy stressor that can induce health effects.

Many health risks are associated with poor IAQ, including asthma. In fact, indoor air is often more polluted than outdoor air, although the nature of the pollutants may be different. The primary method for improving IAQ is the use of ventilation to dilute contaminates filtration, and the control of the source of pollution.