According to the Indoor Air Quality Standard, if doors and windows are closed, formaldehyde exceeding 0. 1mg/m_ cannot survive, otherwise it is very likely to cause harm to human body. If it is only slightly exceeding the standard, it is recommended to ventilate for more than three months before staying. If the formaldehyde exceeds the standard by 2-3 times, in addition to formaldehyde treatment is required immediately.