The new coronavirus particles are round or oval, with a […]
The new coronavirus particles are round or oval, with a diameter of 0.06 ~ 0.14 μm. The main transmission routes are respiratory droplet transmission and contact transmission. High-concentration aerosols in a closed environment may also spread, and the population is generally susceptible.
1. Definition and protection principle
A mask refers to a device that covers the mouth, nose, and jaw of a user to filter particulate matter in the air and block droplets, blood, body fluids, secretions, pollen, dust, etc. Generally, the masks that are mainly suitable for the medical environment are medical masks, and the masks that are suitable for the non-medical environment (such as coal mines, dust workshops, daily protection) are non-medical masks. The protective principle of the mask is closely related to the manufacturing materials and processes, microstructure, etc. The material used to retain particulate matter, such as organic mineral fibers, natural fibers, synthetic fibers or new polymer membranes, etc. The retention principles include gravity settlement, inertia Impact, direct interception, Brownian diffusion, electrostatic adsorption, etc.
2. Classification of non-medical masks
1. Classification by material
(1) Non-woven fabric mask: usually made of non-woven fabric composite layer structure, in which the outer layer and the inner layer are made of non-woven fabrics, and the middle layer is made of melt-blown cloth (referred to as SMS structure), mainly based on physical filtration It is mainly based on electrostatic adsorption filtration.
(2) Cotton gauze masks: masks made of textile fabrics, such as knitted fabric masks conforming to FZ/T73049-2014 "Knitting Mouth Setting", follow GB190842003 "Ordinary Absorbent Gauze Masks" (obsolete) or comply with DB51/T17972014 Gauze masks of the local standard "General technical conditions for ordinary protective masks" DB31/2922003 "Gauze masks for protective".
(3) Paper mask: It has the characteristics of good air permeability, easy to use and comfortable. The paper used complies with GB/T22927-2008 "mask paper" standard.
(4) New material mask
2. Classification by function
(1) Industrial dust masks: masks that protect various types of particulate matter (dust, smoke, mist) in industrial production, comply with GB2626-2006 "self-priming filter type anti-particulate respirator for respiratory protective equipment", and a new version of GB2626-20191 has been released ( Implemented on July 1, 2020), the safety mark certification (LA certification) of special labor protection products, from mandatory certification to voluntary certification in 2015, in which the coal mine industry formulated AQ111-2014 to meet the special requirements for defense against coal dust and silica dust "Self-priming Filter Dust Port for Coal Mine".
(2) Daily protective masks: The protective masks worn by ordinary people to filter out particulate matter in the air pollution environment in daily life conform to GB "32610-2016 "Technical Specifications for Daily Protective Masks".
(3) Ordinary warm mouth: The main function is to protect against cold and warmth, to avoid the cold air directly stimulating the respiratory tract, the outstanding feature is good breathability, the middle sandwich filter has a certain filtering effect. (4) Fashion masks: masks that some people wear for the sake of beauty, covering their face, and pursuing fashion.
3. Classification by filtration efficiency
Filtration efficiency refers to the percentage of the filter element that filters out the target substance under the specified test conditions. It is divided into two types: bacterial filtration efficiency (BFE) and particulate filtration efficiency (PFE). It is a key factor that determines the protective performance of non-medical masks; , YYT1497-201614 stipulates the test method of virus filtration efficiency (VFE) of medical mask protective materials. GB2626-2006 is divided into KN type and KP type according to the filtration performance. KN type is only suitable for filtering non-oily particles, NaCl particles are used as the test medium, and the median diameter (CMD) of aerosol particles is (0075±0020) μm, The geometric standard deviation of the particle size distribution is not greater than 1.86.
KP type is suitable for filtering oily and non-oily particles. Dioctyl phthalate (DOP) and paraffin oil are used as test media. The particle CMD is (0.185±0.020) μm. The geometric standard deviation of particle size distribution is not more than 160. GBT32610 requires that masks have filtering performance for both oily and salty media, and are classified into I, Ⅱ, and Ⅲ according to the filtration efficiency level; China Textile Business Association Group Standard T/CTCA72019 "General Protective Mask" 15 pairs of PFE (non-oily particulate matter) ), BFE have regulations. BFE's test medium is usually selected from bacterial aerosols, the average particle diameter (MPS) is (3.0 ± 0.3) μm, and the geometric standard deviation of the distribution does not exceed 1.5.
3. Relevant standards for non-medical masks
1. National standards
The masks specified in GB2626-2006 "Respiratory protective equipment self-priming filter anti-particulate respirator" are suitable for the protection of various types of particulate matter, and have requirements for filtration efficiency, leakage rate, respiratory resistance, dead space, visual field, air tightness, etc. . The test media according to the filtration efficiency is divided into KN and KP. KN includes KN90, KN95 and KN100, and the filtration efficiency of non-oily particulates is ≥90%, ≥95% and ≥99.97% respectively; KP includes KP90 and KP95 And KP100, the filtration efficiency of oily particles is ≥90%, ≥95% and ≥9997%.
The masks specified in GB/T32610-2016 "Technical Specifications for Daily Protective Masks" are suitable for protection in air-polluted environments. They are resistant to color fastness to rubbing, formaldehyde content, pH, decomposable aromatic amine dyes, filtration efficiency, and leakage rate. Requirements for breathing resistance, etc., where the filtration efficiency test medium is divided into salt medium (NaCl particulate matter), and oily medium includes diisooctyl sebacate (DEHS), paraffin oil, etc. According to the protective effect from high to low, the mask is divided into 4 levels: A level, B level, C level, D level, the corresponding protective effects of each level are ≥90%, ≥85%, ≥75% and ≥65%, The air quality index categories applicable at all levels are: severe pollution, severe and below pollution, severe and below pollution, moderate and below pollution, of which grade A requires the filtration efficiency of salt media and oil media to be ≥95% B, C Grade D requires the filtration efficiency of salty media ≥90% and oily filtration media ≥80%.
GBT22927-2008 "mask paper" standardizes the technical requirements of paper used for processing paper masks, which mainly requires tensile strength, air permeability, brightness, dustiness, fluorescent substances, and hygienic indicators, but does not require protection indicators such as filtration efficiency. GB19084-2003 "Ordinary Degreased Gauze Masks" mainly requires the number of masks, size, warp and weft density, appearance, phosphors, microbial indicators, and also does not require protection indicators such as filtration efficiency. This type of mask is thick, hot, The anti-virus efficiency is low, and the adhesion between the structure and the human face is poor. The filtration efficiency of the 12-layer gauze mask is about 11% to 15%.
2. Industry standards
AQ111-2014 "Self-priming Over-dust Dust Masks for Coal Mine" is suitable for the coal mine industry's need to defend against breathable coal dust and sand dust. The industry standard refers to GB2626-2006 for filtering efficiency, breathing resistance, leakage rate, visual field, Dead space, connection strength, dust holding performance, high and low temperature adaptability are all required. According to the filtration efficiency, it is divided into two levels: CM95 (filtration efficiency ≥950%) and CM99 (filtration efficiency ≥990%). The test medium for filtration efficiency is selected The anthracite dust and silica dust have a CMD of (1.3±0.2) μm, and the geometric standard deviation of the particle size distribution is not more than 220, which is different from the salinity (non-oily) test medium in GB2626-2006 and GB/T326102016.
FZT73049-2014 "Knitted Masks" is suitable for identifying the quality of masks made with knitted fabrics as the main material. The standard refers to GB18401-2010 "National Technical Standards for Basic Safety of Textile Products". The pH value, formaldehyde content, odor, decomposable carcinogens Aromatic amine materials, fiber content, color fastness, and air permeability are required, but there is no requirement for relevant protection indicators such as filtration efficiency, breathing resistance, and leakage rate.
3. Group standards
T/CTCA7-2019 "General Protective Masks" is suitable for the protective masks worn in daily life to filter out pollen, catkins, bacterial particulates, and block the exhalation or spray of pollutants from the nasal cavity or oral cavity. The group standard quotes GB19083-2010. Technical Requirements for Medical Protective Masks" YY0469-2011 "Medical Surgical Masks", requirements for formaldehyde, pH, bacterial filtration efficiency, particulate filtration efficiency, ventilation resistance, heavy metal content, microbial indicators, visual field, BFE≥95%PFE≥80 %, the test method refers to YY0469-2011.
T/CTCA1-2019 "PM25 protective mask" is suitable for people wearing masks to prevent PM25 inhalation in the air. The group standard quotes GB26262006 for formaldehyde, pH, decomposable carcinogenic aromatic amine dyes, microorganisms, filtration efficiency, respiratory resistance, death The cavity and the total leakage rate are required. The product is divided according to the filtration efficiency: Grade 1 F95 ≥ 95% Grade 2 F9090%. Both salty and oily media need to be tested. The test methods and test media are the same as those specified in GB2626-2006.
V. Development of non-medical mask enterprise standards
Retrieval of enterprise standard information public service platform January 27, 2020-February 25, all non-medical mask enterprise standards announced, 102 standards by province distribution is shown in Figure 1. According to the statistical requirements of 102 enterprise standards on the filtration efficiency of salted particulate matter (NaCl), it is found that 39.2% (40 copies) of the enterprise standards do not require this index, and 78% (8 copies) of the enterprise standards require the index to be ≥30% (particulate matter) The filtration efficiency is the same as the requirements of YY0469-2011), the enterprise standard of 10.8% (11 copies) requires the index to be ≥80% (the particulate filtration efficiency is the same as the requirements of T/CTCA7-2019), and the enterprise standard of 37.3% (38 copies) requires the Index ≥90% (particulate filtration efficiency reaches the minimum level requirements of GB/T32610 and GB2626), and the enterprise standard of 49% (5 copies) requires the index ≥95% (particulate filtration efficiency reaches the minimum level requirements of GB19083-2010).
6. Selection and use of non-medical masks and tissue production
The filtration efficiency of saline media (NaClIMMAD is 03μm) is an important reference index for all kinds of masks to protect against new coronaviruses. The general population can refer to "Technical Guidelines for the Selection and Use of Masks to Prevent New Coronavirus Infections in Different Populations" for selection and use. When coordinating the supply and production of masks, relevant departments and production enterprises should take into account the objective needs of local new coronary pneumonia epidemic prevention and control, and organize production according to the number of different risk groups. It is best to mark the filter efficiency level on the packaging for easy statistics and Choose to avoid the infection of the general population due to insufficient quantity and failure of protection, and the shortage of mask resources for high-risk exposed personnel such as medical care caused by the ordinary people occupying the resources of medical masks, while avoiding the waste of resources caused by excess quality and excessive protection.