Research on breathing resistance of haze masks

In response to frequent haze weather, people pay more and more attention to the protection of PM2.5, and wearing anti-haze masks has become a habit. How to improve the wearing comfort of the anti-haze mask and prolong the use time of the mask, ensure that the mask will not feel stuffy for a long time, breathe easily, and also ensure that the filtration efficiency of PM2.5 meets the requirements. important research content. Under normal circumstances, the filtration efficiency of the mask will not decrease with use. On the contrary, as the fine particles are adsorbed on the fabric, the filtration efficiency of the mask may also increase with the length of use. Therefore, this paper focuses on the change of breathing resistance of anti-haze masks with the use of time. This research does experimental research on 8 kinds of PM2.5 protective masks that are popular in the market, basically covering the existing types of anti-haze masks on the market. 24 wearers used it continuously under the condition of sitting still, and the change value of breathing resistance was tested every 1 h. At the same time, the subjective breathing experience of each wearer was interviewed and recorded, and the breathing of the mask was comprehensively evaluated from the test results and the subjective experience of the personnel. The relationship between the resistance and the duration of use has a reference for improving the breathing comfort of the anti-haze mask in the future. 1. The experimental method was tested under the outdoor environmental conditions of mild air pollution, air quality index (AQI) of 124 and moderate pollution, AQI index of 163. The test bench is set up in strict accordance with GB 2626—2006 'Respiratory protective equipment - self-priming filter type anti-particulate respirator' in the breathing resistance test standard requirements, the 8386 multi-parameter ventilation meter was used to detect the pressure in the experiment, with high accuracy. The specific parameters of the anti-haze masks used in the experiment are shown in Table 1. The out-of-lab test adopts the real breathing mode. The breathing resistance value of the mask is tested after the tester breathes freely for 1 hour. The breathing resistance value of each type of mask is tested for 3 masks at a time, and the average value of the 3 results is taken for continuous testing. 6 times. 2. The effect of external resistance on human breathing comfort The vacuum degree (peak negative pressure) in the mask during inhalation and the residual pressure (peak positive pressure) during exhalation are called the external resistance of respiratory protective equipment. If the breathing resistance is too large, it is easy to cause breathing fatigue. Under mild physical load, the maximum fluctuation of oral pressure during breathing caused by the added resistance of respiratory protective equipment does not exceed 7.5 cm H2O, or the increased work of breathing per liter of ventilation does not exceed 0.05 (kg?m)/h, then more than 90% The user will not experience breathing discomfort. It is generally believed that the addition of respiratory resistance will not cause changes in cardiovascular and metabolic aspects, but the air-supplied mask can cause rapid changes in heart rate due to excessive self-weight. Therefore, when making and designing masks, we must consider the respiratory resistance value of masks, whether it will cause human respiratory discomfort, and avoid excessive initial resistance of masks or rapid growth of mask resistance, which will affect the use of masks. The influencing factors of the external respiratory resistance are: ① The greater the total resistance value of the respiratory resistance, the more serious the degree of respiratory discomfort. ②The proportional relationship of respiratory air resistance. Under mild physical load, the inspiratory resistance component has a greater impact on respiratory discomfort; under heavy physical load, it may have a greater impact on expiratory resistance. ③Physical load can not only aggravate the influence of external respiratory resistance, but also increase the threshold of respiratory discomfort. Heavy physical load and high temperature environment can aggravate the influence of external resistance. The interaction between them is“add up”. ④ Significant individual differences, women's tolerance is worse than men's. The laboratory is carried out without physical load, and the influence of the above factors on the experimental results can be ignored. Personal protective masks use human breathing force (generally 30-50 Pa) as the purification power, purify the atmospheric environment to meet the human body's demand for clean air, and have low resistance characteristics compared to the mechanical power in the building environment space. According to GB 2626—The 2006 'Respiratory Protective Equipment - Self-Priming Filtering Anti-Particulate Respirator' standard stipulates that the total inspiratory resistance of various types of masks should not be greater than 350 Pa, and the total expiratory resistance should not be greater than 250 Pa. In the test, the inhalation resistance is 350 Pa and the exhalation resistance is 250 Pa as the pressure value at the end of the service life of the mask. The test results of the initial breathing resistance of 8 masks are shown in Table 1. 3 Experimental results and analysis 3.1 Wearing personnel breathing Among the 24 mask-wearing personnel in the experience experiment, 4 of them wore masks without breathing valve and those with breathing valve successively. During the 6 hours of the experimental test, basically all the testers were able to adapt to the breathing resistance value of the mask. There were no symptoms such as shortness of breath or dizziness during the test. Only one tester had a slight dizziness reaction after 1 hour of the test and terminated the test. The tester was mainly caused by personal physical differences and the habit of wearing masks. The general reflection of the testers is that the mask has poor air permeability and strong breathing discomfort, because when the air permeability of the mask is poor, the gas exhaled by the person cannot be exchanged well with the outside world, resulting in the accumulation of exhaust gas in the mask, and people will have difficulty breathing. , making people feel uncomfortable; when the breathability of the mask is good, the gas exhaled by the person can be exchanged with the outside world well, and the person will feel smooth breathing. From the interview results, compared with the ear-mounted type of masks of the same type, the head-mounted type has a good fit with the face, and the feeling of breathing is slightly stronger. Although the mask fits the face better, the effect of blocking particles is better. The better, but the more airtight the mask, the more obvious the increase in breathing resistance to the human body
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