Dust, bacteria and virus floating in the indoor air are dozens of times or even hundreds of times higher than those outdoors. The air does not circulate in the air-conditioned room, which will accelerate the breeding of bacteria and microorganisms. Air pollution is also likely to occur in a sealed air-conditioned room. Harmful substances such as formaldehyde, benzene and ammonia gas released by indoor decoration and furniture stimulate the respiratory system and induce diseases such as asthma.