Chapter 12: Respiratory care, CPR and blood transfusion
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Definition
Humidity is the amount of water vapour present in a gas. The terms used to define humidity are ‘absolute humidity’, ‘maximum capacity’ and ‘relative humidity’. Absolute humidity is the mass of water vapour that a given volume of gas can carry at a set temperature. When a gas is at its maximum capacity, it is said to be fully saturated. Relative humidity is the ratio of the absolute humidity to the maximum capacity. The warmer the gas, the more water vapour it can hold. Therefore, if the temperature of the gas falls, water will condense out of the gas into the surrounding atmosphere (Al Ashry and Modrykamien [7]).
