Don's Home Products Respirator Smoke and Dust masks

Inhalable Dust	8.0 - 12 µm
Respirable Dust	1.0 - 5.0 µm
Smoke Particle	0.01 - 1.0 µm
Virus	0.02 to 0.4 micron	rhinovirus (cold) = 0.02 µm, Flu = 0.1 µm]

µm - micron - 1 millionth of a meter Inhalable dust - That which enters the body, but is trapped in the nose, throat, and upper respiratory tract.
Respirable dust - Those dust particles that are small enough to penetrate into the lungs.

NIOSH N99 standard - 99.9% at .3 microns 
HEPA filters - 99.97% on .03 micron particles
ULPA filters - 99.99997% on .012 micron particles
N95 – Filters at least 95% of airborne particles. Not resistant to oil.
Surgical N95 – A NIOSH-approved N95 respirator that has also been
 cleared by the Food and Drug Administration (FDA) as a surgical mask.
N99 – Filters at least 99% of airborne particles. Not resistant to oil.
N100 – Filters at least 99.97% of airborne particles. Not resistant to oil.
R95 – Filters at least 95% of airborne particles. Somewhat resistant to oil.
P95 – Filters at least 95% of airborne particles. Strongly resistant to oil.
P99 – Filters at least 99% of airborne particles. Strongly resistant to oil.
P100 – Filters at least 99.97% of airborne particles. Strongly resistant to oil.

• CDC - Centers for Disease Control and Prevention
• Escape respirators are designed to be used only in an emergency to escape from a dangerous area to a safe area. Many of them use a hood with a neck seal instead of a facepiece. They are typically designed for one-time use for a short period, typically 15 minutes to 1 hour.
• Particulate respirators - N95 Typically for sanding, grinding and insulation particles. They are a fabric fitting over the nose and mouth.
• Gas Masks (Air-purifying respirators.) - Usually full face masks with a cartridge nto filter chemical gasses.
  Smoke particles can rapidly clog gas mask filters, and filters with special chemicals are needed to protect against carbon monoxide and other gases that may occur in a fire.
• MERV means Minimum Efficiency Reporting Value - Used for home air filters
• NIOSH - The National Institute for Occupational Safety and Health (CDC)
• NPPTL - National Personal Protective Technology Laboratory (CDC)

Links:
Be Prepared California
Smoke Hoods
Size of small things
Filters > MERV rating
CDC - NPPTL - NIOSH-Approved Particulate Filtering Facepiece Respirators