Which conditions each mask is designed for:
Disposable Surgical Mask:
Standard: must respect ASTM standards, which have 3 levels of protection, FDA and CE approved.
DOES: help protect users from getting others sick through their spit.
DOESN'T: cannot protect healthy people from acquiring an illness.
Disposable KN95 Respirator:
Standard: must meet NIOSH standards.
DOES: help protect users from germs by blocking out at least 95% of small airborne particles if worn correctly.
DOESN'T: cannot protect against gases or vapors.
All of this protective assurance only applies if you wear the mask correctly, and make sure it fits snugly; please combine with hand hygiene and other preventive measures when you wear masks.
Sources: @businessinsider @medicalexpo