Annoyance by local draught -: Effects of temperature and velocity

To study the annoyance caused by air flows directed to the neck, 12 volunteers (6f, 6m, 20-55 yr) each participated in a windless reference and 6 draught sessions, sitting for one hour in a climatic chamber. While environmental temperature was kept at 23 degreesC, the temperature of the emitted air flows was varied in three (23, 21, 19 degreesC) and its velocity in two levels (0.7, 0.9 m/s), respectively. Skin temperatures and the participants' votes on draught perception, annoyance and local cold sensation at various body parts were recorded. Neck skin temperatures at the end of the draught sessions were on average 2.2 to 3.1 degreesC below those of the windless sessions, with a significant influence of air flow velocity, but not of temperature. The percentage annoyed by draught increased throughout the sessions from about 8% to final values of more than 30%, with a maximum of 67% for air flows with 19 degreesC and 0.7 m/s. Statistical analyses revealed only a trend for an effect of air flow temperature on annoyance, whereas velocity had significant effects on annoyance and local cold sensation. The predictions of the precentage of people dissatisfied due to draughts by ISO 7730 were in good agreement with the observed percentages. The results confirm the importance of air flow velocity in the skin cooling effect of draughts, whereas complementary research to quantify the possible contribution of air flow temperatures considerably cooler than the environment to draught annoyance at sensitive body parts are in process.