Air humidity is the ratio of actual water vapor pressure in the atmosphere to saturated water vapor pressure at the same temperature. When the relative humidity is 40%-70%, the human body feels most comfortable and is not easy to get sick. If the indoor humidity is too high, human cells will cause nausea, constipation, loss of appetite, irritability, fatigue, dizziness and other diseases. Living in a place with high humidity for a long time is prone to rheumatism such as rheumatoid arthritis.
When the indoor air humidity is lower than 40%, dust, bacteria, etc. They are easy to attach to mucous membranes, stimulate the throat and cause cough, and at the same time easily cause respiratory diseases such as bronchitis and asthma.
In 2003, China promulgated and implemented the Indoor Air Quality Standard (GB/T 18883). The relative humidity should be 40%-80% in summer and 30%-60% in winter. The suitable indoor humidity for the elderly and children is 45%-50%, and the suitable indoor humidity for patients with respiratory diseases such as asthma is between 40% and 50%.