This investigation is concerned with the determination of velocity pressure loss-factors for HVAC system components using tracer-gas techniques. Experimental work was carried out using an HVAC system and k-factors for various components such as bends, branches, contractions, expansions and orifice were determined. Results were compared with measurements made using a pitot tube and values given in the CIBSE Guide and ASHRAE Handbook. The performance of different types of filters used in HVAC systems was also examined. The constant-injection tracer gas technique was used to develop correlations between the pressure drop and face velocity of a synthetic-fibre filter, bag filter and glass-fibre filter. Results were compared with data obtained using traditional instrumentation.