Odor from Building Air Conditioners: Emission Characteristics, Odor Compounds and Influencing Factors

Abstract

The odor generated by air conditioners is an important factor influencing the perceived air quality in buildings. In this study, different types of air conditioners and air filters were investigated to study the level of odor emission related to the operation state of the compressor, to identify the odor compounds and to analyze the cooling setpoint temperature on emitted odor intensity. Results show that the odor from constant frequency air conditioner use is periodic and stronger than that from variable frequency air conditioner use due to the different operation strategies of the compressor, which affect the evaporation of condensed water on the surface of the cooling coil. Ethyl acetate, acetic acid, 2-ethyl-1-hexanol, acetaldehyde, hexanal, nonanal, toluene and n-hexane are identified as odor compounds by Odor Active Value (OAV), Gas Chromatography/Olfactory/Mass Spectrometry (GC/O/MS) and Flavornet methods. The higher cooling setpoint temperature would lead to stronger odor, due to greater release of hydrophilic odorous compounds from condensed water. In our opinion, reducing the residual condensed water in air conditioners may be the key to control odor emission before purification.