Puts the design of HVAC systems into the context of whole life-cycle use of a building. States that planned preventive maintenance can minimise the risk of a system failure but must be specified by the building owner. Some failures of the internal environment, including sick building syndrome, can be attributed to inadequate preventive maintenance. Explains that the education and training of a designer does not generally equip him to design a system that can be maintained adequately. Proposes action for building owners.

KEYWORDS: Maintenance, buildings, sick buildings, designers.