The cleanliness inspection

The cleanliness inspection should include air-handling
units and representative areas of the HVAC system
components and ductwork. In HVAC systems that
include multiple air-handling units, a representative
sample of the units should be inspected. If the
inspection is being conducted as part of a mold
remediation project in accordance with IICRC Standard
S520, then all components of the HVAC system must be
inspected.
The cleanliness inspection must be conducted without
negatively impacting the indoor environment through
excessive disruption of settled dust, microbial
amplification or other debris. In cases where mold
contamination is suspected, and/or in sensitive
environments where even small amounts of contaminant
may be of concern, environmental engineering control
measures must be implemented and the services of an
Indoor Environmental Professional (IEP) are highly
recommended to determine the overall impact on the
indoor environment.