Experts have proved that activated carbon masks do not intercept PM2.5

In today's ever-changing information technology, with a click of a mouse, information can be quickly transmitted through the network through the crowd. Although it is easy to obtain, it also suffers from false information. From the "salt of salt" storm to Beijing's water security rumors, various pseudo-scientific and pseudo-science have flooded the network, taking into account the public's cognition from time to time, and even seriously jeopardizing social order and security.

Since October, Beijing's hazy days have begun to increase again, and masks have become "recruited goods." Many masks are marked with the banner of blocking PM2.5 during promotions. So, what kind of mask is the most protective in the face of the common fine particulate PM2.5? With this question, the reporter yesterday invited experts to verify the filtering effect of the seven masks.

experiment

Anti-PM2.5 "N95" most awesome

Previously, reporters purchased N95 masks, non-woven masks, PM2.5 masks, activated carbon masks, ordinary three-layer cotton masks, 18-layer medical gauze masks, and surgical masks on the Internet, small commodity markets, pharmacies, and hospitals. The masks, please chemistry professionals, conducted simulated PM2.5 filter contrast experiments on 7 different types of masks.

Into the Chemical Laboratory of the Science and Technology Museum, a set of particle analyzer designed according to national standards has been set up on the operation platform. The foremost of the oscilloscope-like analyzer is a binding cylinder for a fixed mask, and the exhaust fan at the rear end of the experiment box mainly plays the role of negative pressure to attract smoke outside the mask. After the smoke passes through the mask, it passes through a laser dust meter inside the box and can accurately record the number of particles with a diameter of 1 μm or more.

Unlike the previous use of print toners as experimental contaminants, this experiment selected lighter-threaded cigarette dust with a smaller particle size as a contaminant. "Smoke is closer to the actual PM2.5 particles, and the print toner is actually on the order of PM10." Zhou Youhong explained that this set of instruments was produced by Wang Leran, a third-grade student of Beijing Normal University's affiliated experimental middle school, under her guidance. Compared with professional test instruments, the test results are very reliable.

Said that, the non-woven mask with leather straps tightly hooped on the intake cylinder, ignite 3 branch incense, start the exhaust fan. The real-time PM2.5 concentration in the test chamber will rise to approximately 600 μg/m3. After 15 seconds, all 3 ash fumes changed the upward vertical drift direction and were sucked into the experimental equipment through the mask. One minute after the experiment, the PM2.5 particle concentration recorded by the dust meter was 495 μg/m3. This shows that non-woven masks have little effect on the filtration of PM2.5 particles.

The next 18 layers of medical gauze masks were similar in experimental data, but the filtration rate was relatively high. PM2.5 concentrations stabilized at 465 μg/m3 after 1 minute.

Both ordinary cotton masks and activated carbon masks produced dramatic results in the experiment. With a cotton mask, the concentration of PM2.5 quickly rose to 158 μg/m3 in just 5 seconds. After 1 minute, the mask was introduced into the box. The body's PM2.5 concentration reached 613 micrograms/cubic meter. In the activated carbon mask experiment, the PM2.5 concentration quickly exceeded 404 micrograms/cubic meter.

In the N95 mask and surgical mask experiment, the reporter found that the line of cigarette dust on the outside of the mask had been floating vertically upwards. There was almost no phenomenon that had been inhaled into the experimental box. The readings on the dust meter have also been maintained in double digits at 13 μg/m3 and 41 μg/m3, respectively. In the Taobao, Jingdong Mall and other sales of a certain brand of mask PM2.5 experimental results are also good, PM2.5 concentration of 79 micrograms / cubic meter.

expert

Choose the mask to wear well

Experts interpret the experimental results. "From the data point of view, the N95 mask has the best protective effect, and the ordinary cotton mask has the weakest filtering ability." The activated carbon mask is also not a preferred object. Apart from the poor filtration capacity, the activated carbon particles in the filter layer may be rubbed and squeezed. Pressure and other external forces become smaller and become fine particles that can penetrate the nose of the gauze layer.

"N95 masks and surgical masks also have shortcomings, the public should also be considered when choosing." Zhou Youhong added that in the experiment, the line of cigarette dust was not inhaled into the experimental box through the mask, indicating that these two types of masks are less breathable, wearing After Yan Yan will feel depressed.

Professor Fudan University School of Public Health, who has long been concerned about PM2.5 issues, also said that not all masks have a preventive effect on PM2.5. Even if you choose the right mask, wear it properly. "The mask must fit snugly on the face. The mouth and nose breathe completely through the mask filter." He said that masks with better filtering effects tend to have poorer breathability, resulting in increased respiratory resistance and breathing difficulties, and thus suffering from respiratory tract The disease population should be carefully chosen.

Experts suggest that mask types should be selected based on the time of exposure to the environment and their own conditions. If the outdoor trip time is short, you can choose a good filter mask to achieve the best results. For people who spend a lot of time outdoors, they should choose their masks that are both breathable and filterable according to their physical condition. However, no matter which mask you choose, you should reduce outdoor activities when the weather is hazy. When wearing a mask, shave long beard and minimize facial muscle activity and speaking to prevent gaps in the mask and face.

Secret

Porcupine arch helps protect

Experts told reporters that most of the masks that filter better for PM2.5 have added special filter materials. A company official who produces N95 masks told reporters that there is a special layer of filter cloth in the N95 mask. According to technical specifications, this filter can filter particles above 300 nm.

A person in charge of a domestic technology company specializing in the production of PM2.5 protective masks told reporters that the masks produced by the company also embed special Reynolds fibers with a filter rating of 2.5 microns. In addition, microfiltration technology has also begun to be applied to PM2.5 masks.

Experts also said that in practical use, masks with good PM2.5 filtering performance are generally three-dimensional design, that is, the product has a porcupine arch. This design allows the mask to better fit the face. Ordinary flat cutting masks will create gaps with the face when worn.

Extended interview

People who wear masks will choose fewer people

Of the 300 pedestrians and cyclists passing outside the subway Dongsi Station and outside the Chegongzhuang Station, 75 people wore a variety of masks. Among them, the ones that wear the most are disposable non-woven masks and activated carbon masks with metal nose clips. Among the young people, wearing cotton masks with various pattern patterns is the most common.

“What is your protection against wearing a mask?” In response to a reporter’s question, the answer to 30 of the 35 respondents was “PM2.5.” However, when reporters continued to ask how to choose the masks against PM2.5, most people shook their heads and said that they did not know how to choose, nor did they know that the mask they were wearing was geometrically influential in preventing PM2.5 invasion. When choosing a mask, most people will choose the style recommended by the store salesman, but the protection principle and function are not clear.

China Labor Insurance Network