Published: 1972 | Southern Medical Journal, July 1972, Vol. 65, No 7

Humidification to reduce respiratory illnesses in nursery school children

Sale C


This prospective interventional study was done with 515 nursery children (2½ to 6 years old) in three private kindergarten buildings. The author analyzed the effects of four types of intervention: humidification in school and at home (group 1), only in school (group 2), only at home (group 3) and no humidification at all (group 4). Study period: Nov. 1969 to May 1970.

Sale analysed absentee days related to colds, identified by request on teachers, parents and care taking pediatrists. School building 1 was humidified with an average relative humidity of 50%, compared to the humidity of building 2 and 3, where humidity was 10 to 15% lower.

The data is summarized in the table.

Results: reduction of absentee days by almost 50% through humidification at school. A further decrease of absenteeism was achieved by additional humidification at home, while the absentee rates returned to pre-study rates after ending the humidification efforts.

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Doc's view...

by Walter Hugentobler

The results of Sale's study are quite conclusive. Maintaining an indoor humidity of around 50%RH can reduce respiratory infections between children by almost half, when compared to a dry atmosphere below 40%RH.

Sale demonstrated an additional effect by also controlling humidity in the home. This showed itself to be beneficial but not as much as humidification in the nursery environment.

Even though the children spent much longer in the home environment, the risk of infection is less, as exposure to potentially infectious individuals is more limited in the home than the nursery.

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