The relative humidity is lower than 30%. Low humidity and low temperature can accelerate body heat dissipation. At this time, the thermal radiation in the human body is absorbed by the water vapor in the air, which makes people feel cold, causes capillary contraction, pale skin, reduced human metabolism, obstacles in blood circulation and cell metabolism in tissues, and causes tissue malnutrition and frostbite. When the indoor relative humidity is less than 10%~ 15%, dry air will dehydrate nasal cavity, trachea and bronchial mucosa, reduce elasticity, reduce mucus secretion, weaken cilia movement and reduce resistance, so that inhaled dusty bacteria can not be quickly removed, which is easy to induce and aggravate respiratory diseases. Dry air can also cause dehydration of epidermal cells, accelerate keratinization and reduce sebum secretion, leading to rough wrinkling and cracking. In addition, the air is too dry, which will make the dust fly and worsen people's living conditions.
In the dry season, the incidence of diphtheria, influenza, whooping cough, meningitis and other diseases also increased significantly, and the number of attacks of asthma and bronchitis also increased significantly. The main reason is that dry air accelerates the reproduction of influenza virus and pathogenic Gram-positive bacteria, and spreads with dust, resulting in epidemic diseases.
When the room temperature is moderate, the change of relative humidity has little effect on human body. When the temperature is 15. At 5 degrees, the relative humidity changes by 50%, and the impact on human body is only equivalent to the indoor temperature change 1 degree.