A Sydney television station found that sensitive equipment in their transmitter room was being contaminated by large dust particles. Vilair-AAF was asked to investigate the problem, and found that there were two factors responsible for the contamination. The air filters installed in the ventilation system for the room were of relatively low efficiency; and there was some bypass of unfiltered air because of deficiencies in the air filter installation. The filter holding framing system was modified to provide an effective and reliable seal around the perimeter of the filters. A two-stage filter system was then installed – with AAF Amair 300 panel filters as the primary stage protecting AAF BioCel V 95% semi-absolutes as the secondary stage. When the ventilation system was re-commissioned, it was determined that the concentration of airborne particles in the room was at a lower level than had ever been achieved. BioCel V filters are designed for industrial HVAC installations in which HEPA quality air filtration is required. As an H10 EN 1882-classified air filter, BioCel V is ideal for upgrading existing non-HEPA HVAC installations. The filter’s mini-pleat media provides high quality filtration on fine particulates; and because of its 3000 m3/h air capacity, BioCel V is an ideal choice in new installations as fewer filters are needed to handle a given air volume. The lower media resistance results in low energy costs and long service life.