Jan Kaczmarczyk

Human Response to Five Designs of Personalized Ventilation

Human response to five different air terminal devices (ATDs) for a personalized ventilation system (PVS) was studied in an experimental office under well-defined conditions. A group of 30 human subjects assessed air quality and rated their thermal comfort and perception of draft. Two temperature levels, 23°C and 26°C, and two background levels of air quality in the office, high and low, were studied during the experiments. Under all conditions the personalized ventilation system provided outdoor air at a temperature of 20°C. All PVSs allowed for individual control of the airflow rate as well as for adjustments of the supply air direction. Results showed that all ATDs studied significantly improved perceived air quality at the workstation. The greatest improvement was obtained when the pollution level and the temperature in the office were high. The thermal environment created with all systems was assessed as acceptable. Subjects were able to improve thermal comfort with all ATDs studied. The subjects identified which of the tested ATDs they preferred.

Human response to local convective and radiant cooling in a warm environment.

The response of 24 human subjects to local convective cooling, radiant cooling, and combined radiant and convective cooling was studied at 28°C and 50% relative humidity. The local cooling devices used were (1) a tabletop cooling fan, (2) personalized ventilation providing a stream of clean air, (3) radiant panels below and above the desk in front of the desk occupant, and (4) the same two radiant panels but with small fans blowing room air toward the upper panel to be cooled and redirected toward the person. A reference condition without cooling was also tested. The cooling devices significantly (p < 0.05) improved subjects’ thermal comfort compared to the condition without cooling. The acceptability of the thermal environment was similar for all cooling devices. The acceptability of air movement and perceived air quality increased when local cooling methods were used. The best results were achieved with personalized ventilation or the tabletop fan. Only minimal improvement in perceived air quality was reported when the radiant panel was used alone, indicating that in a warm environment, local convective cooling is superior to local radiant cooling as a means of improving perceived air quality. The intensity of the reported sick building syndrome symptoms increased during the exposure time, with or without cooling devices in operation. Air movement had very little effect on sick building syndrome symptoms, but they increased when the pollution level was high. The lowest prevalence of symptoms was reported with personalized ventilation and with the radiant panel with attached fans, which also caused subjects to report less fatigue. Sick building syndrome symptoms increased most when the tabletop fan, generating movement of polluted room air, was in operation. The temperature of the inhaled air rather than any local cooling of the head was associated with sick building syndrome symptoms, although this needs further study. The most preferred cooling method was personalized ventilation for six subjects, fan for eight subjects, and radiant panel (or radiant panel + fans) for nine subjects.