The Guard 3 face mask 10 pack PM 2.5 Filter is defined as "Particulate matter that are 2.5 microns small" which tells you the size of particles blocked completely by the filter. Research shows PM 2.5 filters with a cloth mask will reduce airborne particulates by 90%
Each filter is recommended for about 24 hours of use or about a week of occasional use
Can be used with Guard 3 masks
Not for medical use
No returns, No refunds.