With the arrival of the heating season, the number of haze days is increasing, and the air purifier has once again become the focus of consumption. People's vision

Recently, the Beijing Municipal Environmental Protection Bureau released the air quality status from January to October 2018. From January to October, the PM2.5 concentration in Beijing was 49 micrograms/m3, down 18.3% year on year; The PM2.5 concentration in September was 30 μ g/m3, which was the lowest monthly average concentration since the monitoring. Many people said that the air purifier had not been turned on for a long time.

As the heating season begins, do you want to buy an air purifier this year? What are the precautions for purchase and use? What are the advantages and disadvantages of the purifier and the fresh air system? The reporter interviewed relevant experts to answer your questions.

Do you want to buy air purifier? How to choose?

The purifier should still be a regular spare part at home. Buy "right" instead of "expensive"

Last winter, residents in Beijing Tianjin Hebei region generally believed that there were more good weather, and most of the air purifiers in their homes were idle. Qiu Zhaoyun, General Manager of the Two Clean Products Business Department of Lake Electric Co., Ltd., said that the "panic consumption" of purifiers in the market has disappeared due to the country's heavy efforts to control air pollution and the gradual improvement of air quality. According to industry estimates, the sales volume of air purifiers will decline significantly in 2018, and the overall annual sales volume is expected to be about 40% lower than that in 2017.

So, is the air purifier still a necessity at home this winter? "It's like an umbrella, which people think of and use only in rainy days, but who doesn't have one at home at ordinary times? Although the purifier is basically not turned on in good weather, it can be used when haze comes." Zhao Bin, professor of the Department of Architectural Technology and Science at the School of Architecture of Tsinghua University, said that air quality improvement is a long-term process. At this stage, Air purifier is still an effective means to improve indoor air quality and home environment. Even in developed countries where the annual average level of air quality is high, air purifiers are still very popular.

The purifiers in the shopping malls are dazzling. Consumers can focus on the following elements when shopping:

The first is the clean air volume (i.e. CADR, the volume of clean air provided by the purifier per hour). The larger this value is, the stronger the purification capacity is, but the greater the power consumption and noise are. In addition, the CADR value marked on the commodity is usually the air purification capacity of the maximum gear, which does not represent all gears. Zhao Bin suggested that the CADR value of the air purifier should be 3 times the room volume (room area × floor height), and consumers can convert it according to the residential situation.

"When you buy a purifier, you should only buy the right one, not the expensive one." Zhang Yinping, director of Tsinghua University's Building Environment Testing Center, said that the so-called "right", that is, the purification capacity of the purifier should match the needs of consumers (such as pollutant types, room area), while paying attention to the appearance and noise level and other details. The cumulative purification amount of major pollutants (i.e. CCM, the total amount of pollutants that can be treated by the purifier) should also be considered. The larger the value, the longer the service life of the purifier, and the lower the replacement frequency of the filter screen.

"It's better to buy a cost-effective one than an expensive one. You can calculate the formula 'CADR value ÷ (price × power)', and the larger the value is, the higher the cost performance ratio is." Zhao Bin suggested that some foreign brand purifiers may be more suitable for their own environment, with strong pollen removal function, but the efficiency of removing PM2.5 is not necessarily high. In addition, the current filtration technology is simple and effective, and there is no obvious technical difference at home and abroad. As long as the filter material is qualified and the assembly is standardized, the purification effect can be achieved.

Some purifiers on the market now use technologies such as static electricity and negative ions. Although they have the advantages of quietness and power saving, consumers should be cautious when purchasing and using them. Zhao Bin told reporters that on the one hand, the use of such purifiers is prone to secondary pollution such as ozone, which is harmful to human health. On the other hand, even if the business reports that the ozone and other substances produced by the products meet the national standards, they may only meet the standards in the short term, and pollutants will still accumulate after a long period of continuous operation.

"In the face of a wide range of purifier brands, consumers must pay attention to checking whether the products comply with the national standard GB/T18801-2015. If they do, it means that they have been tested by a qualified third-party organization and can buy with confidence." Qiu Zhaoyun reminded.

How to use the air purifier most effectively?

It should be combined with window opening and ventilation, and the placement position should be particular. The filter element should be replaced regularly

The use of air purifier is also particular. In addition to its own function, the purification effect is related to the placement position. If only one purifier is used in houses of 80-90 square meters or more, the effect will be uneven. For example, the purifier is in the living room while people are in the bedroom. Due to the barrier of the room structure, the concentration of pollutants in the bedroom will take a long time to decline. "It's better to use the purifier wherever people are. Most of the purifiers are mobile, and the filter purifier will not cause harm even if it is close to the human body, so it is recommended to use it in a single room to maximize the purification effect," said Zhao Bin.

It is also important to replace the filter element regularly. Experts explained that if the filter element is used for a long time and has not been replaced, the purification efficiency of the machine will decline; The continuously accumulated pollutants will also make the purifier become a secondary pollution source - the inhaled air "sweeps" over the filter element that has not been replaced for a long time, contaminates the old pollutants and may react with them to generate new pollutants, which are then discharged indoors.

How to determine when to replace the filter element? Experts suggest that you can use a measuring instrument to check the decline rate of indoor pollutants after the purifier is turned on. If it is observed that the decline rate is significantly slower, the filter element should be replaced. However, it is too late to replace the filter element at the stage of "smelling and smelling", which indicates that there are too many pollutants accumulated on the filter element. Zhao Bin said that there is no fixed standard for the replacement period, and the public should comprehensively consider such factors as the degree of pollution, the working time of the purifier and the type of filter element. In the case of heavy haze and frequent opening, the filter element can be replaced every 3-6 months.

The outdoor pollution is serious. When the indoor purifier is turned on, the problem of "whether to ventilate" is a headache for many people - opening the window is afraid of the smog coming in, and if you don't open the window, you will feel panic.

Zhang Yinping believes that even if there is air pollution outside, it is not advisable to completely close doors and windows for a long time. Proper ventilation is still necessary. Fresh air volume is an important indicator of indoor air quality. In addition to providing the air needed for breathing, it can also improve the bad smell in the room, remove excessive moisture, dilute indoor pollutants, etc. In the room with insufficient fresh air for a long time, the human body may have headache, chest tightness, fatigue due to the high concentration of pollutants, and it is also easy to cause respiratory and nervous system diseases. "Opening windows for ventilation is the most direct and simple way to obtain fresh air, but attention should be paid to the timing. The public can check the real-time air quality, and try to open windows at a time of day when the air is relatively good and the temperature and humidity are relatively appropriate."

Zhao Bin said that as long as the windows are open for ventilation, the concentration of indoor pollutants such as carbon dioxide will drop rapidly in about half an hour, and it will take a long time to rise to the high value after the windows are closed. Residents don't have to worry too much about the haze. Because the doors and windows of the building itself isolate some of the outdoor air, the indoor pollutant concentration is generally 1/3 to 2/3 of the outdoor concentration, so the indoor PM2.5 concentration itself is lower than the outdoor concentration. Even if it rises during window opening, it can also be rapidly lowered through the purifier.

"The experimental results show that after the doors and windows are closed, the indoor PM2.5 concentration can be significantly reduced when the purifier is opened for about half an hour. If there is no other indoor pollution source, it can be reduced to less than 5% of the initial concentration after one hour. It is recommended that residents adopt the principle of 'short window opening, long window closing'. If they are not at ease, they can also open the purifier while ventilation." Zhao Bin said.

Which function is better or worse, fresh air system or purifier?

Each has its own advantages and disadvantages. Natural ventilation+air purifier is more conducive to health and energy conservation

In recent years, the "fresh air system" that can filter outdoor air 24 hours without interruption has entered more and more people's homes. There are many products to choose from, such as ducted fresh air system, wall mounted fresh air fan and so on. Compared with air purifier, what are the advantages and disadvantages of fresh air system?

Zhao Bin believes that the fresh air system can continuously introduce and filter outdoor air, and reduce indoor carbon dioxide concentration without opening windows. But it is precisely because of its working principle that the filter device continues to operate, and will soon face the problem of declining energy efficiency. The air purifier absorbs indoor air, and the PM2.5 concentration is not so high after being blocked by buildings; The fresh air system directly inhales outdoor air, so it needs to deal with higher concentration pollutants.

In addition, PM10 and other large particulate pollutants will settle after entering the room, rarely entering the purifier, but will enter the fresh air fan in large quantities outdoors. Under the same conditions, the fresh air system needs to treat three times more pollutants than the purifier, and its consumption of filter materials is also far greater than the purifier. Zhao Bin pointed out that in areas with severe smog, the filter element of the fresh air system needs to be replaced almost once every 1-2 months. And because of the complex structure, it is difficult for consumers to replace by themselves, which requires special personnel to operate. Therefore, the choice of fresh air system means higher maintenance costs.

"The ongoing research by the research team of Tsinghua University has found that if used improperly, the secondary pollution caused by the fresh air system may be more serious than that caused by the air purifier under certain conditions. Whether it can be popularized on a large scale is still questionable," said Zhao Bin.

Zhang Yinping believes that the purifier and the fresh air system have their own advantages and disadvantages. It is difficult to simply say who is good and who is bad. The public can choose appropriate products according to their own needs. "In general, the mode of 'natural ventilation+air purifier' is conducive to both health and energy conservation."

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