Severely cold winter, the people often shut tightly the windows and doors, cold-resistant wind raids human. Does this, although plays to maintain warmth role, but because the air is not counter-flow, causes the indoor air the cleanliness drop to affect the health.

The air maintains life essential material. The adult each time breath\’s air is about 500 milliliters, 1 hour exhales 1000 liters gas, in exhaling in the gas, the carbon dioxide occupies for 4%,1 hours to exhale carbon dioxide about 40 liters, in the air had 4/10000 carbon dioxides, shuts tightly because of the windows and doors, the carbon dioxide will be higher, harm health.

The windowing is frequently advantageous in the fresh air and gorgeous sunlight enters indoor, reduces in the air the carbon dioxide density, makes one feel fresh happy, is not only beneficial to the health, but may also raise the study efficiency.