The mechanism of action of KN90 and KN95 is the same as the size of the non-oily particles targeted, and only 5% difference in particle filtration efficiency is also selectable.
It should be noted that the N level in the US NIOSH standard is only N95, N99, N100, and no N90 ; the KN level in the Chinese GB 2626-2006 standard is only KN90, KN95, KN100, and no KN99.
So masks marked N90 or KN99 can basically be judged as fakes.
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