What is the breathability of masks?

1. The connection between mask breathability and fabric structure

All fabric structures are porous. The relevant research indicates that the pore size is closely related to the fabric's breathability function. Generally, the larger the average pore diameter of the same kind of fabric, the better the breathability. Different fabrics have obvious differences in pore size and air permeability. For the same type of fabric, due to the different fiber materials, yarn linear density, fabric structure, fabric warp and weft density and fabric thickness, the fabric air permeability is also very different. . Because the air permeability of double-sided knitwear is much lower than that of single-sided knitwear, the barrier properties of harmful substances of double-sided knitwear are very good. Non-woven fabrics generally exhibit a single-fiber network structure, which has greater air permeability and harmful substance transmission function. Together, mesh non-woven fabric fibers have more contact surface area, and therefore have a stronger adsorption function.

The relevant research indicates that the fabric permeability shows an obvious downward trend with the increase of the number of layers. Taking cotton fabric as an example, the air permeability will decrease by about 50% from single layer to double layer; while the number of fabric layers added continuously, the decrease tends to be steep; when the fabric layer is added to 6 layers, the air permeability is only single 20% of the layer fabric. Therefore, the relationship between the fabric aperture and the number of layers and air permeability is particularly important in the design of protective masks. When the breathability of the mask is poor, the gas exhaled by the person cannot communicate with the outside world very well, resulting in the accumulation of exhaust gas in the mask, the person will have difficulty breathing, making people feel uncomfortable; when the breathability of the mask is better, the person exhales The gas can communicate with the outside world very well, and people will feel breathing.

2. The connection between mask breathability and filter power

The protective effect of the mask is mainly based on the filtering effect of the mask on the harmful substances. The high filtering power of the mask on the harmful substances is good for the purification of the air. The healthier the air drawn by the human body, the better the protective effect of the mask, and vice versa The worse. The national table has clear rules for the filtering power of masks in different categories. For example, in the technical request of GB19083-2010 medical protective masks, the filtering power of masks used in the medical environment mainly refers to the non-floating air in the filtered air. Oily particles, including viral blood, droplets, secretions, etc. The filter element of this type of mask separates particles of different particle sizes through interception effect, diffusion effect, gravity effect, inertial effect and electrostatic effect. However, there is always such a particle size that cannot be completely filtered, so the filtration of medical masks Power first tests this kind of particles that are difficult to filter and get a useful test result.

For a mask to have a certain comfort, it must have a certain ventilation function. In theory, the difference between the ventilation function of a mask and the filtering power of the mask has a certain correlation. When the breathing function of the mask is extremely poor, the mask itself blocks foreign substances from entering the mask, and then plays a protective effect and does not depend on the filtering power of the mask, but the comfort is also low. It is not suitable for human wear. When the breathability of the mask is better, the material exchange in the surface of the mask is more frequent, which requires higher filtering efficiency of the mask, so as to satisfy the high frequency of material exchange, the mask can filter out the air in a large limit Harmful substances enter the human body, thereby providing a protective effect. The ventilation function of the mask and the filtering power must have a good matching degree to play a very good protective effect, and to establish a model between the ventilation function of the mask and the filtering power, it is particularly necessary to find the relationship between the two.

3. The relationship between breathability and tightness of masks

Having a good filtering power is the basis to ensure that the mask has a protective effect. The gap between the mask and the face is not good, and the gap will occur, and the air flow resistance of the gap is much smaller than the filter material. According to fluid mechanics, it is known that the air flow will preferentially pass from the place where the resistance is small, so no matter how good the filtering effect of the mask is The protective effect of the mask will not be very high. Therefore, the tightness of the dust mask is an important condition for ensuring the protective effect of the mask. The tightness of the mask is generally indicated by the total leakage rate [6], that is, under the conditions of laboratory regular inspection, when the subject inhales, the concentration of the mimic agent and inhalation from all mask parts including the filter element into the mask during inhalation The percentage ratio of the concentration of the mimic agent in the air, the lower the total leakage rate, the higher the adhesion. Therefore, the better the adhesion of the mask, the better the ventilation function of the mask, so that the air can pass through the mask to meet the breathing needs of people. Conversely, the worse the adhesion, the less necessary the breathability of the mask. The mask with good ventilation function requires the mask to have a good adhesion to a certain extent, so as to ensure that the mask has a high protective effect.

Fourth, the effect of ventilation function on the quality of the mask

Face mask. The important quality is the protective effect against harmful substances. Its quality is mainly manifested in the filtering power of harmful substances, the degree of adhesion with the face and the wearing comfort. It can be inferred from the correlation between the permeability of the mask and the filtering power and adhesion that its permeability will affect the protective performance of the mask to a certain extent, that is, affect its quality. The wearing comfort of the mask is mainly manifested in that the breathing resistance is small, the weight is light, it does not irritate the skin, and the wearing and cleaning aspects depend on the breathability of the fabric material or the breathability of the mask. If the ventilation function is good, the comfort of the mask will be high, and the filter power and tightness will be required to be high to ensure its quality. Conversely, when the ventilation function is poor, in order to ensure the protective effect of the mask, its comfort will be reduced, that is, the quality is poor. Therefore, the breathability of the mask directly affects the comfort of the mask, indirectly affects the filtering power and adhesion, and then affects the quality of the mask.

V. Conclusion

Breathability is a characteristic of masks, which depends primarily on the construction and combination of fabric materials. At the same time, the breathability also affects the comfort, filtering power and adhesion of the mask, which in turn affects the quality of the mask. Therefore, establishing a standard for testing the permeability of sexual masks is conducive to improving the standardization system of Chinese masks, protecting the order of Chinese mask stores, and ensuring the health of Chinese mask users.