Published: Mar 1973 | Heating, Piping and Air Conditioning, Vol. 45, No.3

Humidification and Upper Respiratory Infection Incidence

Gelperin A


This retrospective cohort study compared the incidence of upper respiratory infections of two groups of Army recruits, which were accommodated in barracks of identical construction and ventilation.

The barracks of one group were humidified to 40%RH ±5%, while the other barracks had no humidity control and had an average humidity level of 20%RH ±8%.

The study compared the incidence of upper respiratory infections (diagnosed by the Army physician) in the two groups. The inquiry was done in two time periods, 19. Oct. to 19 Dec. 1970 (738 recruits) and 11 Jan. to 20 March 1971 (822 recruits).

The average incidence of upper respiratory infections per trainee was 1.14 in the humidified and 1.33 in the non-humidified group. The incidence of gastro-intestinal, genito-urinary, skin, laceration-contusion or psychological illnesses/disabilities were identical.

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Doc's view...

by Walter Hugentobler

A low indoor humidity has the double impact of allowing airborne germs to remain infectious and airborne for longer, as well as reducing our body's defense against them, through dehydration and impairment of our mucociliary clearance process.

The most striking feature in this study is the fact that the upper respiratory infections suffered by the recruits were clinically confirmed by a physician and written down in a medical record, ensuring a good level of accuracy.

Once more humidification and the use of humidifiers is shown to reduce the incidence of respiratory infections in people occupying the same built environment.

Other scientific studies relating to humidity and health...