Current Research

The Centre has made an internationally recognised breakthrough by demonstrating conclusively that temperature and humidity have significant effects on the perception of air quality (Fang et al. 1999).

It is a common experience that warm humid air seems "more stuffy" than cool dry air, but it has been an open question as to whether there were any effects on perceived air quality (PAQ) and if so, whether this is due only to psychrometric effects on emission or whether psychrometric effects on perception occur as well.

Subjects exposed to low air humidities in the climate chamber.

Researchers at the Centre have performed experiments that separated psychrometric effects on emission from those on perception: in specially developed and very sophisticated equipment, building materials were exposed to a range of different temperatures and humidities while the acceptability of the polluted air was assessed at constant temperature and humidity (Described here).

The materials were also exposed to constant conditions while the acceptability of the polluted air was assessed under a wide range of temperatures and humidities. It was shown conclusively that changes in these two familiar factors do have significant effects on PAQ. As PAQ is as much the "bottom-line metric" for the ventilation industry as thermal comfort is for the heating and cooling industry, this has attracted worldwide interest and offers some new and exciting possibilities for energy conservation in buildings.

In northern Sweden, the Centre has been undertaking a field intervention experiment to determine the limits to low humidity. Outside temperatures of -30C occur during a large part of the winter in Canada, Russia, and Scandinavia, and for shorter periods in the northern parts of China, Mongolia, Japan and Korea. Large numbers of people are therefore exposed to levels of indoor humidity that are well below the minimum level recommended by current standards.

Aircraft operate in outdoor temperatures of -50C and below, and passengers are therefore exposed to even lower levels of humidity. The field experiment in Sweden is the second part of a research contract currently being carried out for ASHRAE.

Test of the mucous ferning in the eye after exposure to very low air humidity.

In the first part of the contract, laboratory exposures at the Centre have already revealed that although an exposure to low humidity (15% and 5% RH at 22(C) for 5 hours, as experienced on medium distance flights, does not lead to very much subjectively-perceived discomfort, it does have small measurably negative effects on the eye, effects which are exacerbated by slightly raised temperatures (above 22C) (Wyon et al. 2002).

References

Fang L, Wargocki P, Witterseh T, Clausen G, Fanger PO (1999) Field study on the impact of temperature, humidity and ventilation on perceived air quality. Proceedings of Indoor Air '99, Edinburgh, Scotland, 2, 107-112

Wyon DP, Fang L, Meyer H, Sundell J, Weirsøe CG, Sederberg-Olsen N, Tsutsumi H, Agner T, Fanger PO (2002) Limiting criteria for human exposure to low humidity indoors. Proc. of Indoor Air 2002, Monterey, CA, pp. 400-405.