The cover of the daily protective mask is made of filter material. The wearer overcomes the resistance of the filter material to the airflow through self-breathing, so it is called a self-priming filter respirator. When inhaling, the low air pressure in the mask causes airflow into the mask; when exhaling, the air pressure in the mask is higher than the ambient pressure, and the airflow is discharged through the mask. When the filter material of the mask meets the requirements of the standard and the mask is close enough to the user’s face, most of the inhalation airflow will be filtered out by the filter material. The daily use of protective masks cannot be 100% close to the face, which is affected by many factors such as face shape, skin smoothness, and whether there are hairs under the mask. Most of the particles inhaled by wearing daily protective masks come from leakage, so the tightness of daily protective masks is the key to ensuring the effective work of the filter. In order to reduce leakage, daily protective masks must be designed with a human body structure, and the headband and nose clip apply a certain amount of pressure to make the mask close to the face.
The materials used to filter particulate matter are mineral fibers, natural fibers or synthetic fibers. There are five types of fiber filter mechanisms for filtering particulate matter in the air, and they can work together.
Settling effect: the large particles in the air flow settle on the filter material under the action of gravity, and are separated from the air flow;
Inertial impact: When the particles in the airflow bypass the filter fibers blocking the airflow, the higher-quality particles will deviate from the airflow direction due to inertia and hit the filter fibers to be filtered;
Retention: The particles are located on the flow line closest to the filter material in the airflow. Since the particle radius is greater than the distance between the flow line and the filter material, the particles are “scraped” and intercepted by the filter material;
Diffusion: due to the thermal movement of air molecules, extremely tiny particles are impacted by air molecules, constantly changing the direction of motion, showing Brownian motion, and randomly touching the filtered filter fibers;
Electrostatic effect: If the filter media fibers have weak static electricity, no matter whether the particles in the airflow are static or not, when they are close to the filter media fibers, they are easily attracted by the static electricity and filtered out. The electrostatic effect can help the filter material to improve the filtration efficiency without increasing the air resistance.
Healthy members of the public are not advised to wear masks in daily life and normal social activities. If you need to contact people with infectious diseases or stay in crowded and poorly ventilated places for a long time, you should wear a mask for personal protection