Can a photocatalytic air purifier be used to improve the perceived air quality indoors?

The effect of a photocatalytic air purifier on perceived air quality (PAQ) was examined in rooms polluted by typical sources of indoor pollution. The rooms were ventilated at three different outdoor air supply rates. The air quality was assessed by a sensory panel when the purifier was in operation as well as when it was off. Operation of the purifier significantly improved PAQ in the rooms polluted by building materials (used carpet, old linoleum, and old chipboard), and a used ventilation filter as well as a mixture of building materials, used ventilation filter and cathode‐ray tube computer monitors. The effect corresponded to approximately doubling the outdoor air supply rate. Operation of the purifier significantly worsened the PAQ in rooms with human bioeffluents, probably due to incomplete oxidation of alcohols which are one of the main pollutants emitted by humans. Present results show that the photocatalytic air purifier can supplement ventilation when the indoor air is polluted by building‐related sources, but should not be used in spaces where human bioeffluents constitute the main source of pollution. Practical Implications The present results suggest that a photocatalytic air purifier can supplement ventilation when the indoor air is polluted mainly by building‐related sources, for example in unoccupied buildings outside working hours when ventilation is considerably reduced or turned off and pollutants build up and adsorb on indoor surfaces. The results also suggest that use of a photocatalytic air purifier should be avoided when humans are present and constitute main source of pollution.