In this paper, we will discuss the home disinfection method is used to treat masks worn daily, and the feasibility of reuse is evaluated by testing the filter efficiency index of masks.
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COVID-19 spread, masks are in short supply in many places, and a variety of home disinfection methods have appeared on the Internet to increase the number of reuses of the disposable masks that come with them, but these are widely circulated.
In order to verify the influence of disinfection methods on the performance of the mask, this experiment selected four disinfection methods as microwave heating, ultraviolet radiation, steaming and medical alcohol spraying that can be used by households with a high degree of transmission, and disinfection treatment was made after the daily wear and use of two types of masks, KN95 daily protection type, and hygienic plane. This experiment selects the key index of mask filtration efficiency to carry out the impact evaluation.
1 Experimental section
1) Equipment
U.S. TSI 8130 automatic filter media tester.
2) Method
Refer to the filtration efficiency test method of GB/T 32610-2016. The air flow rate is 85 L/min, saline media.
3) Experimental samples
A brand KN95 three-dimensional mask (hereinafter referred to as A), B brand hygienic flat mask (hereinafter referred to as B) (Figure 1), brand hygienic flat mask C sample, D sample, E sample, F sample. D sample, E sample, F sample (Figure 2), the number of samples in each group was two, and the results were taken as the average value was taken.
4) Home Disinfection method
a. Home microwave oven disinfection method
Sterilization parameters: remove the nose clip wire, medium 300 W, front and back
4 min each.
Note: To disinfect in a microwave oven, be sure to remove the shaped nose clip (with metal wire inside) close to the nasal bridge, otherwise melting or burning may easily occur.
b. Household UV lamp disinfection method (UVCA 38W UV lamp)
Disinfection parameters: UVCA 38W UV lamp irradiation 15 min, spacing 20 cm.
Note: Please strictly follow the product instruction manual for sterilization of household UV lamps.
c. Medical alcohol (75%) disinfection method
Parameters: Spray with a household spray bottle to ensure the surface of the mask is moistened.
d. Home steamer – hot steam disinfection method
Parameters: Electric steamer heated and steamed with hot water at 100 ℃ for 20 min.
5) Experimental design
A wearing cycle of 4 h was used. Parallel sample groups were blank (not worn), worn (not treated), worn + treated (primary treatment), worn + treated + worn + treated (secondary treatment).
2 Results and Discussion
The filtration efficiency before and after disinfection in four ways is shown in Table 1
Table 1 Filtration efficiency before and after home disinfection in 4 ways
| Processing | A primary treatment filtration efficiency /% | A secondary treatment filtration efficiency /% | B primary treatment filtration efficiency /% | B secondary treatment filtration efficiency /% |
|---|---|---|---|---|
| Blank (not worn) | 99.8 | 99.8 | 83.4 | 83.4 |
| Wearing (not processed) | 99.6 | 99.6 | 81.7 | 81.7 |
| Microwave heating | 99.5 | 99.4 | 81.4 | 77.4 |
| Steam heating | 99.6 | 99.5 | 75.0 | 74.1 |
| Ultraviolet radiation | 99.7 | 99.0 | 76.8 | 73.8 |
| Alcohol spraying | 97.3 | 97.2 | 55.6 | 47.3 |
As can be seen from Table 1: The overall effect of the four disinfection treatments on the filtration efficiency of Brand A KN95 masks was not significant. Among them, 75% alcohol spraying has the greatest effect on the filtration efficiency, but after two cycles of wearing, it only decreased by 2.4 percentage points. Microwave heating, water vapor heating, ultraviolet radiation 3 disinfection treatment methods have a certain impact on the filtration efficiency of B brand ordinary flat mask, the first cycle filtration efficiency decreased by 0.3, 6.7, 4.9 percentage points; the second cycle filtration efficiency decreased by 4.3, 7.6, 7.9 percentage points. 75% alcohol spraying has a greater impact on the filtration efficiency of B brand disposable hygienic flat mask The filtering efficiency of disposable hygienic flat masks of brand B decreased by 4.3, 7.6, and 9 percentage points respectively in the second cycle. After the first and second treatments, the filtration efficiency decreased by 26.1 and 34.4 percentage points.
Four new disposable hygienic flat masks, sample C, sample D, sample E, and sample F, were treated with 75% alcohol spray and soaking (10 min) to further verify the effect of alcohol on the filtration efficiency of the masks.
Table 2 Filtration efficiency after spraying and soaking with 75% alcohol
| Processing | C filtration efficiency /% | D filtration efficiency /% | E filtration efficiency /% | F filtration efficiency /% |
|---|---|---|---|---|
| Before processing | 82.6 | 81.2 | 79.1 | 65.5 |
| Spraying | 62.6 | 64.8 | 68.8 | 60.7 |
| Soak | 42.6 | 28.5 | 52.1 | 48.5 |
As can be seen from Table 2: After 75% alcohol treatment, the filtration efficiency of all four masks decreased to a large extent, with individual masks dropping by 52.7 percentage points.
The flat masks and KN95 masks worn by the public are basically SMS structured with 3 layers of polypropylene (PP): single spun bond layer nonwoven on both sides and single or multi-layer melt-blown layer nonwoven in the middle. The melt-blown filter layer in the middle carries a large amount of electrostatic electret process. The electrostatic adsorption effect can be generated to substantially improve the filtration efficiency of the mask. PP is a hydrophobic material with a moisture content PP is a hydrophobic material with a moisture content of 0% and does not swell with water and affects the porosity. Therefore, alcohol causes the decay of the surface charge of electrostatic electret materials, thus reducing the electrostatic adsorption effect. This reduces the electrostatic adsorption effect.
This experiment did not verify the effectiveness of the four treatment methods for bacterial and viral disinfection and only referred to the recognized effective disinfection methods such as the fifth edition of the Pneumonia Treatment Protocol for COVID-19 Infection and the disinfection process of the bioaerosol laboratory YaoLab.
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3 Conclusion
In the daily wear scenario of the public in non-special places, it is feasible to reuse the masks after disinfection treatment in three ways: water vapor steaming, microwave heating, and UV lamp irradiation. Water vapor, microwave, and UV light have little effect on the electrostatic standing poles of the melt-blown layer of the mask, while alcohol has a greater effect on the electrostatic standing poles.
References
[1] Conversion and standard comparison of particle size for mask filtration efficiency testing[J]. YANG Xiaobing,CHENG Jun,ZHANG Shouxin,YAO Hong,LU Lin,DING Songtao. Journal of Textile. 2020(08)
[2] The protective effect of masks against new coronavirus and the method of reuse after sterilization[J]. Liu Yanbo,Hao Ming,Liu Lingling,Liu Yao,Cai Bingsio,Chen Zhijun. International Textile Herald. 2020(02)
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