To help maintain good indoor air quality (IAQ) in schools, guidance for the development and implementation of an effective program for maintenance and operation of heating, ventilating, and air-conditioning (HVAC) systems are discussed. Frequently, a building's occupants will complain about IAQ when the temperature or humidity are at uncomfortable levels. Such extremes in humidity or temperature can lead to respiratory distress and other problems. To manage IAQ, facilities managers must take the lead and ensure that an effective plan is in place for dealing with HVAC maintenance and other matters. Such plans usually begin with an IAQ profile, which includes an audit of the HVAC and related systems. Documentation is an important component of the plan, as is ensuring that all personnel are properly trained. HVAC commissioning, in which performance and design are verified using computerized controls to monitor the HVAC system, are other vital aspects of an HVAC plan. When such plans are not in place, or even when plans fail, some of the consequences for IAQ include inadequate ventilation, malfunctioning controls, excessive humidity, odors, and irritating vapors. (Contains 4 figures and 18 sources for further information.) (RJM)