据推测，冬季呼吸道疾病的增加是由于室内相对湿度降低，增加了空气中细菌和病毒的存活时间。本文报道了六所学校的通风和湿度对每立方米空气中菌落形成单位数（cfu/m）的影响。空气中发现的细菌主要是非致病性的，在12月、1月和2月出现了少量致病性细菌。cfu/m3的数量主要是占用率的函数。在非占用期间，cfu/m的数量在40到70之间，学生一进入教室，cfu/m的数量就增加到300到700。cfu/M3的平均水平在很大程度上取决于空气再循环率，因为过滤器去除了90%的空气细菌。 普通过滤器能有效去除空气中的细菌，并可用于将建筑物中的空气细菌降至最低。随着相对湿度的降低，教室空气中细菌的数量略有减少，这不支持冬季呼吸系统疾病增加的假设。然而，它们主要是非致病性的，病原体在相对湿度下可能有不同的存活模式。总的来说，教室中的空气细菌水平主要取决于占用率和通过过滤器的空气再循环率。

It is hypothesized that the increase in respiratory diseases in winter is caused by the reduced indoor relative humidity increasing the survival time of airborne bacteria and viruses. This paper reports the effect of ventilation and relatives, humidity upon the number of airborne colony forming units per m3(cfu/m ) in six schools. The airborne bacteria found were mainly non-pathogenic with a few pathogenic bacteria appearing in December, January and February. The number of cfu/m3were mainly a function of occupancy. In non-occupied periods the number of cfu/m were in the range of 40 to 70, this increased to 300 to 700 as soon as the students entered the classroom. The average level of the cfu/m3was largely a function of the air recirculation rate because the filter removed 90% of the airborne bacteria. Ordinary filters were effective in removing the bacteria from air and could be used to minimize airborne bacteria in buildings. The number of classroom airborne bacteria were reduced slightly as the relative humidity decreased which does not support the hypothesis proposed for the increase of respiratory illnesses in winter. They were, however, mainly non-pathogenic and the pathogens may have a different survival pattern with relative humidity. In general, the level of airborne bacteria in the classroom were mainly a function of occupancy and air recirculation rate through a filter.