humidity

The impact of dry indoor air on comfort and health in winter was investigated in a crossoverintervention study in two floors of an office building in northern Sweden. The indoor airhumidity (normally 10-20% RH) was raised to 23-24% RH, one floor at a time, using steamhumidifiers. Questionnaires and objective (clinical) measurements were applied.

We conducted an epidemiological study to examine the associations between indoor climate and office workers’ health and working efficiency. We investigated four office buildings in Massachusetts, USA, beginning May 1997 over 1 year. Ninety-eight participa

Sick building syndrome (SBS) symptoms were investigated in a laboratory study of low humidity environments: 30 subjects were exposed to clean air at 22C with 5%, 15%, 25% and 35% RH and 30 were exposed to polluted air at 18C, 22C and 26C with a constant moisture content of 2.4 g/kg dry air and at 22C/35%RH. The subjects were exposed to each condition for 5 h and reported the intensity of SBS symptoms. Five hours of exposure to clean air at 5% RH caused only eye symptoms, while 5 h of exposure to polluted dry air at 15% RH aggravated a number of symptoms of the skin, nose, throat and lips.

The thermal comfort response of Korean college students was investigated in a thermalenvironment chamber both in summer and winter seasons. Eight thermal conditions consistingof four air temperatures (24, 26, 28, 30C) and three relative humidities (40, 60, 80%) wereselected in summer. Eight thermal conditions consisting of five air temperatures (18, 20, 22,24, 26C) and two relative humidities (40, 60%) were chosen in winter. In each test, sevenfemales or seven males were questioned in the chamber for 3 h, where thermal and comfortsensations were surveyed every 15 min.

Thermal manikin test and subjective experiments with a desktop based task conditioningsystem were carried out in a climate chamber of Kanto-Gakuin University, Japan. Theexperiments were conducted under three different combinations of ambient air temperatureand relative humidity. It was found that skin temperatures at the upper half of the manikinsbody exposed to the supply air were decreased. Setting of task condition was fixed at first, andthen the subjects were allowed to control the environment freely after a certain period in thesubjective experiments.

Subjective tests with a desktop-based task conditioning system were conducted. Previous tothe subjective tests, detailed measurements of air velocities influenced by the system wereperformed. For subjective experiments, three ambient air temperature and relative humiditycombinations, (1) 27C/40%RH, (2) 30C/40%RH and (3) 30C/70%RH, were applied. Eachof 16 college age subjects was exposed to the three different experimental room airconditions.

The aim of that study was to assess the impact in an office environment of absolute and relative humidity, temperature and humidification on workers' skin and upper airway symptoms (such as nasal or pharyngeal dryness, eyes problems, congestion). Physical factors associated with symptoms and perceptions were appraised with logistic regression models.

This presentation will review two major microbial cell wall agents (MCWA) - endotoxin and (1->3)-ß-D-glucan - concerning their toxic effects after inhalation and their role for the development of symptoms among persons in buildings with humidity problem.

Japanese Building Maintenance Law defines that indoor humidity shall be maintained not lower than40%. But it is sometime very difficult to comply with the law. Indoor air humidifies in office buildingsmostly below 40% especially in wintertime. A request to deregulate the provision arises from HVACindustries. But a question concerning risk to deregulate the lower limit of humidity is arising.According to researches in 1960s, activity levels of influenza virus become higher when indoorrelative humidity becomes lower than 40%.

This is a personal set of comments giving the author's impressions of the papers presented at the conference. A great concern of him is the difference between building scientists and health scientists as indoor air quality issues are investigated.