The present invention relates to an
air decontamination apparatus, the apparatus comprising: a housing having an air inlet, an air outlet, an air flow passage between the air inlet and air outlet; an
ozone measuring device arranged to detect a concentration of
ozone at or near the air inlet; a hydroxyl generator located downstream of the
ozone measuring device; an
ultraviolet emitting device located downstream of the hydroxyl generator; an
ozone depletion catalysing device comprising a catalytic surface, wherein the or each
ultraviolet emitting device is arranged such that
ultraviolet light emitted from the ultraviolet emitting device is incident on the catalytic surface; a
hydrocarbon emitting device downstream of the
ozone depletion catalysing device, the
hydrocarbon emitting device being arranged to emit a
hydrocarbon in a variable amount; and an air
stream generator arranged to generate and direct an air
stream from the air inlet to the air outlet, through or across the hydroxyl generator, ultraviolet emitting device,
ozone depletion catalysing device and hydrocarbon emitting device, wherein the apparatus further comprises a
control unit arranged to control the hydrocarbon emitting device to emit a hydrocarbon in an amount determined in dependence on an amount of ozone detected by the ozone measuring device. In further aspects the invention relates to a method of
air decontamination and management of ambient
ozone concentration and an ultrasonic diffuser for use in an
air decontamination apparatus.