110 MODERN FRUIT MARKETING 
attention need be paid to ventilation, because the open- 
ing of the doors and windows to control the tempera- 
ture will give sufficient fresh air for practically all 
purposes. 
In large storage houses ventilation is attended to 
regularly and considerable care must be exercised to 
get the right kind of air and at the right temperature 
and humidity. For fruit storages, ventilation is pre- 
ferably given at least twice a week. And certain pre- 
cautions must be taken. First, the temperature of the 
outside air needs to be almost the same as that inside 
of the building. If it is impossible to do this, air is 
first introduced into the cooling chamber and the proper 
temperature secured before bringing it into contact with 
the stored fruit. 
Second, the humidity of the air introduced must not 
vary materially from the humidity in the storage room. 
For this purpose, certain tests are made to determine 
moisture content of the air and if care is taken it is 
usually possible to get an atmospheric condition outside 
the storage room which will be about the same as the 
requirements of the humidity inside. Then by rapidly 
introducing the air this moisture content can be main- 
tained. 
Humidity of Cold Storage Houses.—By humidity is 
meant the amount of water vapor in a given space, and 
this is usually calculated by weight in grains per cubic 
foot of air space. In all storage houses, considerable 
attention must necessarily be given to the amount of 
moisture in the atmosphere surrounding the stored 
products. This is especially true in the case of fruit. 
If the humidity runs lower than required, the fruit will 
