Humidity indicates air's dryness or wetness, expressed as absolute or relative humidity. Absolute humidity refers to water vapor mass in 1m³ wet air, while relative humidity is the ratio of actual to maximum water vapor at the same temperature.
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Answer: The physical quantity that indicates the dryness or wetness of air is called humidity. Commonly used humidity expressions are: absolute humidity and relative humidity.
Under standard conditions, the mass of water vapor contained in 1m³ volume of wet air is called the "absolute humidity" of wet air, and the unit is g/m³. Absolute humidity only indicates how much water vapor is contained in a unit volume of wet air, but cannot indicate the ability of wet air to absorb water vapor, that is, it cannot indicate the degree of humidity of wet air. Absolute humidity is also the density of water vapor in wet air.
The ratio of the actual amount of water vapor contained in wet air to the maximum amount of water vapor that can be contained at the same temperature is called "relative humidity", which is usually expressed by φ. Relative humidity φ is between 0 and 100%. The smaller the φ value, the drier the air and the stronger the water absorption capacity; the larger the φ value, the more humid the air and the weaker the water absorption capacity. The moisture absorption capacity of moist air is also related to its temperature. As the temperature of moist air increases, the saturation pressure increases accordingly. If the water vapor content at this time remains unchanged, the relative humidity φ of the moist air will decrease, which means that the moisture absorption capacity of moist air increases. Therefore, when installing the air compressor room, attention should be paid to maintaining ventilation, lowering the temperature, and eliminating drainage and water accumulation in the room to reduce the moisture in the air.
