In-place testing of installed systems can be performed, if required, including leak testing of filters and frames, penetration testing of filters, and photometer testing of UVGI systems. In-place testing of building air cleaning systems can be used to demonstrate or prove the effectiveness of these systems. The measurement of airborne concentrations of naturally occurring building microbial flora using air sampling provides a reliable means of demonstrating the performance of any air cleaning retrofit, as well as highlighting any existing air quality problems. Testing is typically performed prior to installation of components and results compared with post-installation levels of airborne bacteria and fungi. The reduction in airborne biocontaminants after a few days or a few weeks of system operation will demonstrate to the client's satisfaction that the system is operating per design and that indoor air quality is improved.

Additional testing for cooling coil disinfection systems will be performed to demonstrate the cleanliness of the coils or other air handling unit internal surfaces. Surfaces will be sampled for mold contamination before any retrofit, and then sampled one or more times during the following days or weeks. Often, this type of installation results in complete sterilization of the internal AHU surfaces.