N95 masks vs. other masks: Facial fit and certification

N95 respirator masks are considered the holy grail of face coverings, and the one considered by medical professions to be the most effective at protecting the wearer from acquiring the coronavirus.
N95 masks
N95 masks differ from other types of surgical masks and face masks because they create a tight seal between the respirator and your face, which helps filter at least 95% of airborne particulates. They might include an exhalation valve to make it easier to breathe while wearing them. Coronaviruses can linger in the air for up to 30 minutes and be transmitted from person to person through vapor (breath), talking, coughing, sneezing, saliva and transfer over commonly touched objects.
Each model of N95 mask from each manufacturer is certified by the National Institute for Occupational Safety and Health. N95 surgical respirator masks go through a secondary clearance by the Food and Drug Administration for use in surgery -- they better protect practitioners from exposure to substances such as patients' blood.
In US health care settings, N95 masks must also go through a mandatory fit test using a protocol set by OSHA, the Occupational Safety and Health Administration, before use. This video from manufacturer 3M shows some of the key differences between standard surgical masks and N95 masks. Homemade masks are unregulated, though some hospital websites point to preferred patterns that they suggest using.