Cotton masks

These only provide protection against heat or cold.

The surface of the mask has large pores and cannot filter fine particles with a particle that may be as small as 2.5 microns. Some cotton masks with a filtering effect of more than 90% have very high airflow resistance, and you will experience difficulty when breathing when wearing them.

Ordinary gauze mask

These offer no barrier to PM5 (Particulate Matter 5) or less.

The most common flow blocking principle of a gauze mask is a mechanical barrier layer. Via this layer, large particles can be blocked, but particles with a diameter of less than 5 microns cannot be blocked, let alone PM2.5 particles.

Ordinary medical masks

These are very useful for PM4.

Disposable medical surgical masks and disposable medical masks can block particles larger than 4 microns in diameter. According to general medical standards, for 0.3 micron particles, the permeability of medical surgical masks is 18.3%, and the equivalent for an ordinary disposable medical masks is 85.6%.

Active carbon masks

These does not increase protection efficiency.

Active carbon masks can reduce some peculiar smells, but the protection efficiency of particles is not significantly enhanced. Active carbon itself is a kind of particle, that may be a hazard for patients with chronic respiratory diseases or inhale.

N95 masks

Most PM2.5 are blocked.

Medical N95 masks can block the flow of large particles. When tested in an airtight laboratory, the transmission rate of a medical N95 mask is only 0.425%. It can be said that more than 99% of the particles are blocked.