Measurements and Prediction of Inhaled Air Quality with Personalized Ventilation

This paper examines the performance of five different air terminal devices for personalized ventilation in relation to the quality of air inhaled by a breathing thermal manikin in a climate chamber. The personalized air was supplied either isothermally or non-isothermally (6°C cooler than the room air) at flow rates ranging from less that 5 L/s up to 23 L/s. The air quality assessment was based on temperature measurements of the inhaled air and on the portion of the personalized air inhaled. The percentage of dissatisfied with the air quality was predicted. The results suggest that regardless of the temperature combinations, personalized ventilation may decrease significantly the number of occupants dissatisfied with the air quality. Under non-isothermal conditions the percentage of dissatisfied may decrease up to 4 times. INDEX TERMS Personalized ventilation, Perceived air quality, Inhaled air temperature, Improved IAQ practices and technologies, Offices INTRODUCTION Previous research has shown that air temperature, air humidity and the level of air pollution influence the perception of air quality. Fang et al. (1998a, 1998b) confirmed earlier studies and found that the odour intensity of air did not change significantly with temperature and humidity; however, air is perceived less acceptable with increasing temperature and humidity. This impact decreases with an increasing level of air pollution. A linear correlation was found between acceptability and enthalpy of the air in the case of facial exposure as well as of longer 20-min whole-body exposure. The concept of personalized ventilation suggests supplying clean air directly and gently into a person’s breathing zone. It is assumed that occupants’ satisfaction and productivity can be increased as a result of improved air quality and preferred thermal environment. Therefore, the system aims to ensure both a high quality of the inhaled air and individual thermal control for the occupants. In order to improve the quality of the inhaled air, clean personalized air should reach the breathing zone unmixed with the polluted room air. The velocity should be low in order to avoid draught. Because of the positive influence of low air temperature on the perception of air quality, it would seem to be advantageous to supply cool air. In this case, however, the jet of personalized air may not reach directly the occupant’s breathing zone due to buoyancy forces, which are proportional to the temperature difference between the personalized and room air. Furthermore, an interaction of the personalized airflow with the free convection * Contact author e-mail: [email protected] Proceedings: Indoor Air 2002