Air movement--good or bad?

UNLABELLED

Air movement--good or bad? The question can only be answered by those who are exposed when they are exposed. Human perception of air movement depends on environmental factors including air velocity, air velocity fluctuations, air temperature, and personal factors such as overall thermal sensation and activity level. Even for the same individual, sensitivity to air movement may change from day to day as a result of, e.g., different levels of fatigue. Based on existing literature, the current paper summarizes factors influencing the human perception of air movement and attempts to specify in general terms when air movement is desirable and when it is not. At temperatures up to 22-23 degrees C, at sedentary activity and with occupants feeling neutral or cooler there is a risk of air movement being perceived as unacceptable, even at low velocities. In particular, a cool overall thermal sensation negatively influences the subjective perception of air movement. With occupants feeling warmer than neutral, at temperatures above 23 degrees C or at raised activity levels, humans generally do not feel draught at air velocities typical for indoor environments (up to around 0.4 m/s). In the higher temperature range, very high air velocities up to around 1.6 m/s have been found to be acceptable at air temperatures around 30 degrees C. However, at such high air velocities, the pressure on the skin and the general disturbance induced by the air movement may cause the air movement to be undesirable.

PRACTICAL IMPLICATIONS

Based on existing literature, the paper summarizes factors influencing the human perception of air movement and attempts to specify in general terms when air movement is desirable and when it is not.