The outdoor smog is so serious, is the indoor air quality safe?

In autumn and winter, smog is particularly serious in some areas. Health-conscious friends will wear masks when they go out, and air purifiers will be turned on at home and in the office. Some friends also think that after closing the doors and windows, the indoor air will be "cleaner" than the outdoor air, and you can escape the smog by hiding indoors, but is this really the case?

Will there be smog indoors?

In fact, various countries have corresponding ventilation standards for residential buildings, public buildings and industrial buildings. In this respect, the national standard of civil buildings in China is Code for Design of Heating, Ventilation and Air Conditioning of Civil Buildings (GB50736-20 12). Therefore, even if the building doors and windows are completely closed, there is still a certain air exchange rate due to the infiltration of wind pressure. According to the national standards, rooms with closed doors and windows should keep 1 1- 17 times of air exchange with the outside world every 24 hours (see the table below):

The smaller the per capita living area, the higher the required air exchange times. Wind pressure infiltration and cracks in doors and windows, indoor and outdoor air is mixed many times every day, and there is little difference between indoor air quality and outdoor air quality in foggy days, so it is useless to close doors and windows.

The School of Mechanical and Energy Engineering of Tongji University has done research and found that the indoor PM2.5 level is stable at 90% of the outdoor level in severe haze weather. In addition, doors and windows are closed, ventilation is insufficient, carbon dioxide remains indoors, VOC emitted by furniture, smoking, kitchen fumes and so on. , it may also make indoor air quality lower than outdoor.

How to ensure indoor air quality?

1. air purifier

So what should be done to ensure indoor air quality? I can't wear a mask indoors. After all, the limited comfort of masks also prevents beauty lovers from "showing their faces".

Principle of air purifier, red line indicates www.bj-hyjdwx.com of main filter layer.

This requires the use of an air purifier. The purification function of air purifier mainly depends on various filter layers (filter elements), including HEPA layer, activated carbon layer and catalytic layer. If there is someone in the room all the time, it is best to keep the air purifier on all the time, and don't turn it off soon. At the same time, open the window every morning and evening 15 minutes or more. After opening the window, the air purifier should be turned to the maximum gear to ensure that the indoor air can quickly return to the purified state after ventilation. After that, it can run at a low speed to maintain the air quality within the normal range.

2. Fresh air system

Working principle of fresh air system in glktjn.com

The fresh air system has the function of ventilation and purification, and some have the function of heat exchange. For houses with fresh air system, ventilation is guaranteed, and HEPA (High Efficiency Air Filter) in fresh air system will play a role in purifying air. At this time, whether to turn on the air purifier indoors at the same time depends on the indoor air quality. The simple way is to turn on the air purifier and see if the AQI value (air quality parameter) is within the normal range. As for the online air quality test paper (including formaldehyde test paper), the error is very large, and it is more accurate to rely on your own sense of smell or personal feelings. Professional air quality testing instruments are more than 10 thousand yuan, so the testing expenses of professional institutions can not be close to the people at present.

What should I do in foggy weather?

To sum up, hiding indoors can't escape the smog. Even if the doors and windows of the room are closed, the indoor air quality can not be guaranteed, and harmful gases such as carbon dioxide and lampblack are too high because of poor air circulation, which affects health. In areas with severe smog, indoor air purifiers or fresh air systems need to be equipped. In order to be healthy, you must do personal protection when you go out in foggy days, such as wearing a mask when you go out, and washing your nose with normal saline or sea salt water at home. The reason for cleaning the nasal cavity is that many particles are deposited on the nasal mucosa in the smog every day, such as PM2.5 and PM 10.

V.qq.com diagram of nose washer

There is no doubt that a healthy life needs a certain cost. If you choose N95 mask, the ordinary brand will probably need one from 3-5 yuan. A mask can be used for about 5 days if it is only used during commuting hours. Nasal cavity cleaning solution is usually 0.9% sea salt water or 0.9% physiological saline, and pure water can be used temporarily when there is no physiological saline. At present, the mainstream models of major brands are around 3000 yuan. Fresh air systems are expensive, ranging from tens of thousands to hundreds of thousands. It is expected that the air quality will get better and better in the future, and everyone can breathe fresh and clean air.