Irritation & Discomfort
In general, the reported levels of irritation were very low. There were no occurrences of the 'strong' irritation response, but every condition had at least one 'slight' irritation response. The responses for general irritation are shown below.
In addition to the question on general irritation, participants were asked whether they experienced any discomfort in specific areas (previously identified as areas sensitive to discomfort). These results are given below.
It can be seen that the level of irritation, both general and specific, is very low and there are no significant differences between the conditions. A possible explanation for the discomfort experienced is that the diffuser head is located quite close to the participant's head, and the air is therefore still moving quite fast as it strikes their face (causing eye/nose/lip irritation). Another explanation would be that the design of the system leads to thermal stratification around the participants, i.e. the air around their head is noticeably warmer than that around their hands or feet, and this has been known to cause discomfort.
There are some possible design changes to try and eliminate these low levels of irritation, but overall this is a positive result for the system: most people find it acceptable.