About the N95 /medical face mask's disadvantages, you have to know

Summary:

1) A poor fit can reduce efficiency for PM2.5 from 95% reduce to 78% dut to air leaking.

The sealing is depending on your facial shap and hair. Make sure the mask is securely closed.

2)The level of oxygan is reduced from 21% to 17%, so you can not wear N95 face mask for more than 4 hours.

3) It is not suitable for everyone to wear.