Cars & Driving
- noun in some exhaust emission control systems, e.g. thermal reactor or two-bed converter, secondary (outside) air is added to the exhaust to ensure sufficient supply of oxygen to promote oxidation of HC and CO, thus converting these pollutants into harmless water vapour and carbon dioxide
- Air that is introduced into a burner above or around the flames to promote combustion, in addition to the primary air that is premixed with the fuel or forced as a blast under a stoker.
- Air already in an air-conditioned space, in contrast to primary air that is supplied to the space.