kn95 filtration efficiency:

The two standards of China and the United States for "filtration efficiency" testing are essentially judging the filtering process of a specific area of ​​filter material under specific temperature and humidity conditions and "pretreatment", and 200mg of 0.3μm particles at an air flow rate of 85L/min. The lowest filtration efficiency that appears.

These particles are classified into "oily particles" and "non-oily particles".

N and KN both refer to the test of non-oily particles (the specific test substance is NaCl), and the number represents the level of the filtration result of the filter layer.

Note: The Chinese standard NaCl particles are "counting median diameter 0.075μm", and the American standard is "aerodynamic mass median diameter 0.3μm"-and after the national standard is converted, it is actually the same particle as the American standard.

The numerical meaning of the Chinese standard is as follows (they minus "K" can directly become the meaning of the number of masks of this level in the United States, but there is no "90" level in the American standard.):

Important differences between China and the United States:

The biggest impact on the ultimate protective effect of the respirator is often not because of the filter material, but because of the actual wearing.

The main difference between the American standard and the Chinese standard is reflected in the "respirator wearing requirements", especially the "fitness/fitness" requirements and judgments.

The U.S. Occupational Safety and Health Administration (OSHA) will mandate that all users of respirators undergo testing and training (selection, specific wearing, hygiene, disposal, etc.) before use. The training is usually carried out at the same time as the suitability test. Moreover, the user's physical condition will be evaluated in advance.

In terms of "fitness/fitness", the United States has a complete set of mature systems and professional testing tools to help employees who need to wear these respirators to determine whether a respirator is suitable for them (it can fit well when worn by the person) , And will check this "whether suitability still holds" at least once a year. The user needs to check the tightness of the respirator that is suitable for him every time he wears the respirator that has been procedurally tested.

China is basically at a "blank-primary stage" in the construction of this "system".

China's respirator will test the wearing conditions of 10 testers-95 masks in the test of government agencies. If the wearer's specific number of actions during the test "total leakage rate does not exceed 11%", it will be passed.

Note: The mass median particle size of the non-oily particles tested by KN at this time is 0.6μm, while the oily particles tested by KP are still 0.3μm.

The requirements for the "total leakage rate" of the respirator when worn by each level are as follows:

The problems with this test are:

Although the face shape of the tester is representative, after all, it cannot be exactly the same as the face shape of the actual wearer of the product;

The wearing style and tightness of the tester can not be exactly the same as the actual wearer.

Therefore, whether a respirator passes the KN test, it is actually impossible to judge its protective effect in the actual wearing process of the actual wearer.

Therefore, it is particularly important for the wearer to carefully check the tightness, find a suitable mask and a suitable way of wearing it, and read the product description carefully.

Note: Although respirator products with rigorous and detailed "instructions for use" are not necessarily reliable, the instructions for use of reliable respirator products are almost all rigorous and detailed-or, in other words, respirator products with too simple instructions are usually Need to be extra careful.