The significance of air velocity and turbulence intensity for responses tohorizontal drafts in a constant air temperature of 23 degrees C

Aim: The aim was to prove the significance of air velocity and turbulence i ntensity on the responses to drafts and if air velocity is adequately weigh ted in the draft rating model (DR-model) proposed in ISO 7730 (1994). Metho ds: Seventeen healthy persons (9 women, 8 men, 19-51 yr) took part in 12 ra ndomly arranged l-h sessions where horizontal drafts were directed towards the dorsolateral body sites of the sedentary persons. Mean air velocity was varied in 4 ((<(<nu>)over bar>: 0.1, 0.2, 0.3, 0.4 mis) and turbulence int ensity in 3 steps (Tu: < 30, <approximate to> 50, > 70%) but were kept cons tant during the single sessions, whereas air Velocities were increased ever y 15 min in the basic experiments performed for the DR-model. Air temperatu re was 23 degreesC. humidity varied between 40% and 60%. Subjective percept ion and annoyance due to drafts were registered every 5 min using a list of prescribed body parts and skin temperature was measured continuously throu ghout the sessions at the forearm and at the neck. Results: Draft-induced g eneral annoyance (if draft-induced annoyance was stated for at least one bo dy site) and draft-induced local annoyance as stated for the neck and for t he forearm increased with air velocity and/or with turbulence intensity. Th e decrease in skin temperature, however, was only related to air velocity b ut not to turbulence intensity. Air velocities are obviously not accurately weighted in the draft-rating model(lSO 7730, 1994). As compared to the eff ects observed here, the effects predicted with the DR-model were smaller in case of mean air velocities of 0.3 m/s and less but greater for 0.4 m/s. C oncerning rather sedentary persons it seems that drafts are tolerable as lo ng as mean air velocities do not exceed 0.2 m/s and as long as turbulence i ntensity remains below 30% in air temperature of 23 degreesC.