Abstract: An air ventilation system, comprising an air inlet for admitting contaminated air into the ventilation system, an air outlet for discharging decontaminated air from the ventilation, and an ultra-violet light source disposed therebetween. The ventilation system has a filter disposed upstream of the ultra-violet light source. The filter has a grease particle separator with at least two layers of expanded metal associated therewith. Each has a predetermined number of apertures forming a reticulum. A cartridge filter may be provided for each grease particle separator and disposed upstream thereof. Each cartridge filter and associated grease particle separator preferably forms an integral filtering unit and may be placed at any location of the system.