Effects of Temperature and Humidification in the Environment.

Respiration is enhanced when heated humidification is employed. This is likely due to a reduction in side effects associated with upper airway symptoms and a more refreshed feeling upon awakening. Compliance gains may be realized sooner if patients are started with heated humidity. The hot air coming from a furnace humidifier can help realize those health gains. ______________

The study took place in 2 wings of the building. During the experiment, after a random selection, 1 of the wings was humidified and the other remained non humidified. After 1 wk, the humidification was switched. During the total study period of 6 wk, the population in the 2 wings was exposed to humidification for 3 1-wk periods and to non humidified conditions that corresponded to 3 1-wk periods. Determinants of interest were temperature in each office and air humidification. In a baseline questionnaire administered at the beginning or the study, we obtained information about personal characteristics and variables concerning work-related factors and the work environment.

During the 6-wk experiment, the participants completed a daily structured questionnaire that contained queries about symptoms of acute respiratory illness, time spent in the office, symptoms of dryness (scale of 0 to 3), and the sensation of dryness (scale of 1 to 5) during each work day. The outcomes of interest were symptom scores, which we calculated with the information provided in the daily symptom reports: (1) dryness symptom score (0-12), which included skin symptoms (i.e., dryness, irritation, or itching), nasal dryness, and pharyngeal dryness; and (2) SBS symptoms score (0-6), which included combined symptoms of SBS (i.e., skin, eye, nasal, and pharyngeal symptoms, headache, and lethargy). The sensation of dryness was coded as 1 (too humid) to 5 (too dry).

At the beginning of the study, each of the two groups studied included 180-190 clerical workers. Individuals were eligible for the study if they did not have or use a humidifier in their office. Those who had completed the baseline questionnaire were eligible for participation in the experiment. In the final analyses, we included individuals who had filled in the baseline questionnaire acceptably and who had spent at least 2 hr in the office during which time they had suffered no symptoms of acute respiratory illness.

To grasp the direction and strength of the association of outcomes and temperature during and without humidification, we fitted a multiple linear-regression model for each outcome. In addition, we used analysis of covariance to calculate adjusted means for the outcomes in 5 temperature categories. Given the skewed distributions and heteroscedasticity of the outcomes,[4] we assessed the statistical significance of the linear association by the method of Cochran-Mantel-Haenszel (CMH).[5] For the CMH method, we classified outcomes in 3-4 categories that contained approximately equal numbers of participants. Calculations were made with a personal computer and version 6.12 SAS statistical software.

Results
Study population and indoor air quality. At least one diary was returned by each of 230 workers during the non humidified period and by 233 workers during the humidified period. There were no statistically significant differences between the non humidified and humidified periods with respect to personal characteristics or with respect to characteristics of the work environments. Numbers of subjects, mean temperatures, and corresponding relative humidities are provided in Table 1.

Table 1.-- Characteristics of Environmental Conditions in Various
Temperature Category

Dry Non humidified air

Standard Deviation SD
Relative Humidity %
Temperature deg C
Atmospheric Pressure [bar]x
Population n

Humidified air

Standard Deviation SD
Relative Humidity %
Temperature deg C
Atmospheric Pressure [bar]x
Population n

Temperature effects. The regression coefficients indicating change in the outcome variable per 1 [degrees] C of temperature during the non humidified and humidified periods from the multiple linear-regression models are given in Table 2. The statistical significance of the association, expressed as a p value in Table 2, is the result of CMH analysis. The corresponding adjusted means of the outcomes from the covariance analysis in the 5 temperature categories during both periods of study are shown in Figure 1.

Table 2.--Association between Room Temperature and Symptoms and Air
Dryness in Non humidified and Humidified Conditions

Dry Non humidified air

Humidified air

Discussion

Validity of results. The non experimental study design raised the possibility that selection bias (i.e., people chose offices with a most-suitable temperature) occurred. The crossover design of this study eliminated such a problem. The opening of windows likely provided compensation for the temperature rise caused by humidification. Both mechanisms tended to dilute the effects of humidification and temperature on the symptoms and perceptions we studied.

Synthesis with previous knowledge. Researchers have studied the role of high indoor air temperatures and/or humidification as determinants of symptoms and perceptions in non industrial workplaces and in several types of settings. In this study, we compared our results with those reported in a summary presented by Mendell and Smith,[6] as well as with results of reports published subsequently. Consistent with the present findings, the entity defined as SBS symptoms was increased during high-temperature conditions in 4 of the 7 studies in which this issue was addressed.[1,7-9] In 3 of the 7 studies, investigators found no association.[10-12] In none of these studies did researchers find a decrease in SBS symptoms with high temperatures. High temperature increased the sensation of dryness.[1,3,7] Humidification reportedly decreased the prevalence of SBS symptoms or dryness of airway symptoms only, in 5 of 1 1 assessment studies.[2,3,9,13,14] In 3 of 11 studies, an increase in SBS symptoms occurred during humidification.[11,12,15] In 1 of the 11 studies, a reanalysis of 6 previous studies did not produce a correlation between humidification and SBS symptoms.[6] In the present study, we found a lower level of SBS symptoms, compared with the non humidified conditions, and there was an alleviation of the sensation of dryness during humidification.[2,14] We found that dryness increased more acutely as temperature increased in non humidified conditions.

The results of this study strengthened the evidence that an indoor temperature in excess of 21 [degrees] C or 22 [degrees] C is likely to increase dryness symptoms of the skin and upper airways and to increase the total number of symptoms than can be related to SBS syndrome. The sensation of dryness increased at higher indoor temperatures. Humidification alleviated dryness symptoms and the sensation of dryness. Use a whole house humidifier, also called furnace humidifiers.

This study was supported by The Finnish Work Environment Fund.


__________

Whole House Humidifier

Cures Winter Dryness.

Winter comes with its share of problems from nasty weather to chapped lips and dry skin. We can't fight the weather, but we can do something about dry air with a whole house humidifier, according to Sean McCarthy with the Aprilaire(R) Center for Indoor Air Comfort. "Once you turn the heat on, the air in your home gets thirsty and sucks moisture out of your body, causing symptoms like dry, itchy skin, a sore throat and chapped lips," McCarthy said. Catherine Koester used to dread the effects of heated indoor air. Each winter the Laurel, Md. woman says she went through a great deal of skin lotion to try to ease her parched skin. "I had such a terrible problem, I was literally scratching my legs raw," she said. "My skin was flaking off and it was not a pretty sight." In Koester's case, relief arrived in the form of a whole-house humidifier she had installed in the ductwork of her heating system. "A friend recommended the humidifier, so I checked into it," Koester said. "I thought it might offer some relief, and it has. Once the humidifier was installed and ran for several days, I started to feel more comfortable. My legs stopped itching and flaking. It was a wonderful feeling." Koester also credits proper humidification for helping to improve her chronic sinus problems. "The congestion and headaches I had were greatly diminished after the humidifier was installed," she said. A whole-house humidifier provides proper humidity to the entire home, not just one room, according to McCarthy. "When selecting a whole-house humidifier, we recommend looking for an automatic model with a built-in computer to continuously measure, control and deliver the optimum amount of indoor humidity -- in the range of 35 to 50 percent," McCarthy said. "You never have to worry about adjusting it because the automatic technology produces the right amount of humidity all the time." McCarthy also recommends selecting an evaporative-type model that distributes moisture as a pure water vapor, with no droplets or mist that can carry impurities, like minerals or bacteria. For more information about whole-house humidifiers, visit the e-humidifiers.com

How Much Humidity Do You Need Proper water output capacities for humidifiers. Figures are in gallon per 24 hours

Humidification not necessary to maintain conditions of 70 degrees F and 30% relative humidity.

An amount of approximately 2 gallons per 24 hours provided by internal sources of humidity (based on a family of four) has already been deducted from the above values.