Omron NE-C29-UK Professional CompAir Compressor Nebuliser The unique combination of the Omron Comp Air Pro compressor with Virtual valve technology (VVT) means more of the aerosol is a respirable size and available to the patient to inhale. The VVT's unique design means there are fewer parts to lose and less to clean. This also means that the unit is more hygienic and easier to maintain.