The generation and countermeasures of PM2.5 in residential interior
With the development of society, the whole people pay more and more attention to health. Since the reform, China’s economy has developed rapidly, but at the same time, air quality has deteriorated due to pollution caused by transportation, construction, agricultural activities, combustion sources and particulate matter. According to medical statistics, people need to breathe more than 20,000 times a day. How to improve the living environment and reduce people’s exposure time in harsh air has become the first task to study healthy buildings.
First, the background of outdoor PM2.5
Air pollution is an environmental pollution that is closely related to everyone’s health. Among them, PM2.5, which is a particle with a diameter of 2.5 microns or less, can penetrate directly into the lungs and enter the blood through the lung barrier due to the complex mixture of solid and liquid organic and inorganic substances. Its concentration is often used as air pollution. synonym. In recent years, various urban agglomerations and regions have taken measures to improve air quality.
According to the results of the indoor PM2.5 pollution big data released by Tsinghua University in 2019, there is a positive correlation between indoor PM2.5 concentration and outdoor concentration. Sometimes indoor PM2.5 is higher than indoors. At the same time, the results also show that the indoor level of the office environment is slightly better than the living environment. A lot of statistics suggest that about 80% of the time in the building is in the building, and then subdivided, about 30% is in the office building, and 50% is in the residential home. So let’s analyze how indoor PM2.5 comes from in the living space and how to deal with indoor PM2.5 more economically and reasonably.
Second, the source analysis of indoor PM2.5
In the building interior, as a space, the source of PM2.5 inside is roughly divided into two categories: indoor production and outdoor input. Among them, indoor self-production generally includes cooking, smoking, and personnel activities. Outdoor input sources include the introduction of fresh air systems, the penetration of door and window systems, and the introduction of personnel access.
In areas where decentralized heating is used, gas fireplaces are often used in residential households, even with conventional coal combustion, which is heated by burning calories from fossil dyes. And this combustion process will produce a large amount of nitrogen oxides, which will greatly deteriorate the indoor PM2.5 condition if it cannot be eliminated promptly and effectively.
When we cook at home, there are two processes that produce PM2.5. One is that gas stoves burn natural gas or even particulate matter produced by gas. The second is cooking, especially the soot particles produced by frying and frying in Chinese food. According to the experimental research on four cooking methods of steaming, boiling, frying and frying according to the environmental protection public welfare organization ‘Natural University’, boiled corn, steamed steamed bread and potato chips were tested under the condition that the doors and windows were closed and the range hood was not opened. , PM2.5 produced by four cooking methods. The data showed that ‘cooking’ had a smaller effect on PM2.5, while ‘fried’ and ‘fried’ had a significant effect. Among them, “fried” even reached the ‘explosive table’ level of 787 μg/m3.
In addition to being a bad habit of smoking, smokers in the enclosed indoor space are also the main source of indoor PM2.5. Once there was laboratory test data, a cigarette burned completely, producing 0.62 grams of particulate matter, of which PM2.5 accounted for about 30% to 40%, about 0.19 to 0.25 grams. If you smoke three cigarettes in a 100 square meter room, the concentration of PM2.5 will reach 955μg/m3, and the standard will reach 20~30 times!
4. Personnel activities
Personnel activities include walking, coughing, and secondary dust generated during housework. It should be specially noted that the conventional vacuum cleaner has the function of removing dust, but in fact, the vacuum cleaner is just one of the important sources of indoor PM2.5. The principle of the vacuum cleaner is to use the vacuum negative pressure caused by the electric motor to inhale dust and air in the room, and filter it through the filter to discharge the clean air. The filter in the conventional vacuum cleaner on the market can only filter out large particles of dust, such as dusty pompons that can be seen by the naked eye, but cannot be filtered for fine particles such as PM2.5. Thus, the PM2.5-rich particles are again discharged by the vacuum cleaner. Considering the air disturbance caused by air intake and discharge, PM2.5, which may have been adsorbed and settled, is accelerated by the vacuum cleaner. Of course, there is also a solution to use a high-efficiency vacuum cleaner that filters PM2.5. Similarly, the relatively low-level sweeping robots in the past two years may remove large particles of dust visible to the human eye. However, if the filtration efficiency is insufficient, the indoor PM2.5 can be twice diffused. The principle is the same as that of a conventional vacuum cleaner.
5. Fresh air system
The home fresh air system is undoubtedly one of the more familiar configurations of healthy living in recent years. The main function of the fresh air system is to filter the fresh outdoor air into the room. Then the problem comes. Fresh air refers to the outdoor air rich in oxygen, and even if the outdoor air is filtered by PM2.5, some PM2.5 that has not been filtered is sent into the room, so the new system is from a certain degree. In fact, it is actually an input source for indoor PM2.5, even if some fresh air systems have exhaust function.
6. Door and window system
The windows and doors on the market are now very airtight and can block the flow of air. However, PM2.5, which is less than 2.5μm, can penetrate into the room through the fine gap of the door and window through the free diffusion of Brownian motion.
Third, several common measures to improve indoor PM2.5
After talking about the source of indoor PM2.5, we should choose the right way to improve the indoor environment. It is necessary to solve the problem of ‘open source’, that is, reduce the input of outdoor PM2.5 to the room, and increase the interior of indoor PM2.5. Filter and process. Considering that people’s living habits are hard to change, we mainly analyze the following common measures: improving the airtightness of the outer window, adding new air blowers, and purchasing mobile air purifiers.
1. External window air tightness
Under normal circumstances, the construction engineering standard requires that the airtightness of the outer window should not be lower than the 6th grade specified in GB/T7106, and the corresponding air permeability is 1.5≥q≥1.0 m3/m.h. The unit of this indicator is not difficult to see, this represents the volume of air permeating the length of the outer window per unit length per hour. This is a minimum requirement, but it may often be different due to the quality of the construction or the actual effect of the door and window product process. Considering the severe situation of outdoor PM2.5, doors and windows as the main barrier to block the penetration of outdoor PM2.5 into the room, we should first ensure that the airtightness of doors and windows is maximized, including the selection of good sealing materials, and improve the assembly quality of doors and windows.
2. Home user-type new fan
On the basis of the basic measures to meet the airtightness of the outer door and window, the current active measures are to install a new type of fan or purchase an air filter. The main function of the new air blower unit is to introduce fresh outdoor air into the room, replace the dirty air in the room, improve the oxygen content of the indoor air, and continuously remove harmful gases such as odor and formaldehyde/VOC. However, if it is to remove PM2.5, its effect on improving PM2.5 is not obvious. After calculation, when the outdoor PM2.5 concentration is 200μg/m3 heavily polluted, a 120m2 apartment type house is equipped with a 230m3/h new air blower unit (0.7 gas exchange, meeting national specifications), which takes about 180 minutes. That is, at 3 hours, the indoor PM2.5 concentration reached a stable value of about 60 μg/m3, and did not reach the level of excellent air quality.
3. Mobile air purifier
Since the internal circulation mode of the new wind turbine group has a certain improvement in indoor particulate concentration compared to the fresh air mode. Then consider another measure, using a separate air purifier. In general, we will set up air purifiers in different rooms. Then install a living room (40m2) in the house to install a common CADR of 400m3 / h air volume, air purifier. Within about 30 minutes of using the air purifier, indoor PM2.5 can be reduced to below the national health standard of 35μg/m3. In the end, it can reach the WELL Healthy Building Standard (15μg/m3) and the WHO Air Quality Guidelines (10μg/m3) in an hour or so. It is not difficult to see that the air purifier circulating in a large air volume is very effective in improving the indoor PM2.5 compared with the fresh air system.
Olansi Healthcare Industry portable air purifier is willing to work with more families to further study and manage family indoor issues and contribute to more family health.
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