Research on the Respiratory Resistance of Haze Respirators

In response to frequent haze weather, people are paying more and more attention to the protection of PM2.5, and it has become a habit to wear anti-haze masks. How to improve the wearing comfort of anti-haze masks and prolong the use time of the masks, to ensure that the masks 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 masks will not decrease with use. On the contrary, as fine particles are adsorbed on the fabric, the filtration efficiency of masks may increase with the length of use. Therefore, this article focuses on the changes in the respiratory resistance of anti-haze masks with the duration of use. This study conducted an experimental study on 8 types of PM2.5 protective masks that are popular on the market, basically covering the existing types of anti-haze masks on the market, and selected 24 wearers used it continuously while sitting still, and tested the change of respiratory resistance every 1 hour. 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 two aspects of the test results and the subjective feelings of the wearers. The relationship between the resistance and the duration of use is a reference for improving the breathing comfort of haze masks in the future. 1　 The experimental method was tested under the outdoor environmental conditions where the air pollution is light pollution, the air quality index (AQI) is 124 and moderate pollution, and the AQI index is 163. The test bench is set up in strict accordance with the requirements of the respiratory resistance test standard in GB 2626-2006 'Respiratory Protective Equipment-Self-priming Filtered Anti-Particulate Respirator'. In the experiment, the 8386 multi-parameter ventilation meter is used to detect the pressure, which has high accuracy. The specific parameters of the experimental anti-haze masks are shown in Table 1. The outdoor test in the laboratory adopts the real breathing mode. After the testers breathe freely for 1 hour, the respiratory resistance value of the mask is tested. Each type of mask is tested for the respiratory resistance value of 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 in the mask during inhalation (peak negative pressure) and the residual pressure during expiration (peak positive pressure) are called the external resistance of respiratory protective equipment. Excessive respiratory resistance can easily cause respiratory fatigue. Under mild physical load, the maximum fluctuation of oral pressure during breathing caused by the additional resistance of respiratory protective equipment does not exceed 7.5 cm H2O, or the increased breathing work per liter of ventilation does not exceed 0.05 (kg?m)/h, then more than 90% The user will not feel uncomfortable breathing. It is generally believed that external respiratory resistance will not cause cardiovascular and metabolic changes, but the air-supply mask can cause rapid changes in heart rate due to excessive weight. Therefore, when making and designing masks, we must consider the breathing resistance value of the mask, whether it will cause human breathing discomfort, and avoid excessive initial resistance of the mask or excessive increase of the resistance of the mask, which affects the use of the mask. The influencing factors of the external respiratory resistance are: ① The greater the total resistance value of the respiratory resistance, the more severe the respiratory discomfort. ②The proportional relationship of respiratory air resistance. Under mild physical load, the inhalation resistance component has a greater impact on the sense of respiratory discomfort; under severe physical load, the exhalation resistance may have a greater impact. ③Physical load can aggravate the impact of external respiratory resistance and increase the threshold of breathing discomfort. Heavy physical load and high temperature environment can aggravate the impact of external resistance. The interaction between them is 'additive'. ④The individual difference is significant, and the tolerance of women is worse than that of men. The laboratory is carried out under the condition of no physical load, and the influence of the above factors on the experimental results can be ignored. Personal protective masks use human breathing power (generally 30-50 Pa) as the purification power to purify the atmospheric environment to meet the human body's demand for clean air, and have low resistance characteristics relative to the mechanical power in the building environment. According to the GB 2626-2006 'Respiratory Protective Equipment-Self-priming Filtering Anti-Particulate Respirator' standard, the total resistance of various masks in inhalation should not be greater than 350 Pa, and the total resistance of exhalation should not be greater than 250 Pa. In the test, the inspiratory resistance is 350 Pa, and the exhalation resistance is 250 Pa as the pressure value at the end of the life of the mask. The test results of the initial respiratory resistance of the 8 masks are shown in Table 1. 3　Experimental results and analysis 3.1　The breathing of the wearer Among the 24 mask wearers in the experience experiment, 4 of them wore masks without breathing valve and then with breathing valve. During the 6 hours of the experimental test, almost all testers were able to adapt to the breathing resistance of the mask. There were no symptoms such as shortness of breath or dizziness during the test. Only one tester had a slight dizziness after the test for 1 hour and the test was terminated. The tester was mainly caused by personal differences and unaccustomedness of wearing masks. The testers’ general reaction is that the mask has poor air permeability and strong breathing discomfort, because when the mask’s air permeability is poor, the air exhaled by a person cannot be exchanged with the outside world, resulting in the accumulation of exhaust gas in the mask, and people will have difficulty breathing. , Make people feel uncomfortable; when the breathability of the mask is good, the air exhaled by the person can be well exchanged with the outside world, and the person will feel unblocked breathing. According to the interview results, the head-wearing type and the ear-wearing type of the same model of mask have a better fit to the face and a slightly stronger sense of breathlessness. Although the mask fits better with the face, it has the effect of blocking particles. The better, but the more airtight the mask, the more obvious the increase in respiratory resistance to the human body and the harder it is to breathe. Compared with masks of the same model, with breathing valve and without breathing valve, there is no big difference in the sense of breathing from the perspective of personnel experience.

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