Field investigations reporting increased airborne particles concentrations after ventilation duct cleaning (DC) and emissions of biocides following its use in DC highlight a need to protect building occupants from possible exposures to these harmful pollutants. A new test protocol was developed and applied on 2 buildings to include assessments of duct surface cleanliness and harmful airborne pollutant associated with DC. Using the protocol, duct surface cleanliness was found to be acceptable in a building but post-DC dust level in the other was higher than the recommended 0.75 mg/100 cm². (0.75 mg/15.5 inch².). The protocol has found no airborne particle and fungi emissions attributed to the DC activities in the 2 test buildings. However, an increased emission in airborne organic alcohol compound was noted after DC in a building using biocides. The application of this test protocol on 2 buildings in Canada has demonstrated that harmful airborne pollutant concentration levels attributed to DC activities can be determined while still maintaining cleaning efficiency. The guidelines provided in the protocol can be useful to building operators for their maintenance program and assessment of building occupancy post DC.