The periodic

The periodic cleaning of HVAC systems may be necessary to ensure delivery of acceptable air to the indoor environment. Cleaning may be required on older systems that have not been properly maintained, damaged systems, or in special cases such as following extensive indoor or outdoor construction activities. HVAC system cleaning is expensive and potentially disruptive to normal operations so all possible sources of IAQ problems should be investigated and corrected prior to determining the need for system cleaning.  Frequent cleaning of HVAC systems should not be required if the system is properly maintained as outlined in Chapter 3 of this document.