Indoor humidity should reach 45%~70%. Humidity is very important to the baby's respiratory health. The basic requirement is to keep the humidity around 45%~70%. If the baby lives in the south, it can generally meet the indoor humidity standard. However, for babies living in the northern region, certain measures should be taken indoors to meet the above humidity standards. If the humidity is too low, the baby's respiratory mucosa will be dry, which will reduce the mucosal defense function and damage the ciliary function of the respiratory tract, which will inevitably reduce the baby's resistance to bacteria and viruses and cause respiratory infections.