The size of contaminants and particles are usually described in microns, a metric unit of measure where one micron is one-millionth of a meter. There are 25,400 microns in one inch. The eye can see particles to about 40 microns.
The size of some Contaminants and Particles are Indicated in the Table Below.
Particle | Particle Size (microns) |
one inch | 25400 |
dot (.) | 615 |
Eye of a Needle | 1230 |
Glass Wool | 1000 |
Spanish Moss Pollen | 150 – 750 |
Beach Sand | 100 – 10000 |
Mist | 70 – 350 |
Fertilizer | 10 – 1000 |
Pollens | 10 – 1000 |
Cayenne Pepper | 15 – 1000 |
Textile Fibers | 10 – 1000 |
Fiberglass Insulation | 1 – 1000 |
Grain Dusts | 5 – 1000 |
Human Hair | 40 – 300 |
Human Hair | 60 – 600 |
Dust Mites | 100 – 300 |
Saw Dust | 30 – 600 |
Ground Limestone | 10 – 1000 |
Tea Dust | 8 – 300 |
Coffee | 5 – 400 |
Bone Dust | 3 – 300 |
Hair | 5 – 200 |
Cement Dust | 3 – 100 |
Ginger | 25 – 40 |
Mold Spores | 10 – 30 |
Starches | 3 – 100 |
Red Blood Cells | 5 – 10 |
Mold | 3 – 12 |
Mustard | 6 – 10 |
Antiperspirant | 6 – 10 |
Textile Dust | 6 – 20 |
Gelatin | 5 – 90 |
Spider web | 2 – 3 |
Spores | 3 – 40 |
Combustion-related – motor vehicles, wood burning, open burning, industrial processes |
up to 2.5 |
Fly Ash | 1 – 1000 |
Milled Flour, Milled Corn | 1 – 100 |
Coal Dust | 1 – 100 |
Iron Dust | 4 – 20 |
Smoke from Synthetic Materials | 1 – 50 |
Lead Dust | 2 |
Face Powder | 0.1 – 30 |
Talcum Dust | 0.5 – 50 |
Asbestos | 0.7 – 90 |
Calcium Zinc Dust | 0.7 – 20 |
Paint Pigments | 0.1 – 5 |
Auto and Car Emission | 1 – 150 |
Metallurgical Dust | 0.1 – 1000 |
Metallurgical Fumes | 0.1 – 1000 |
Clay | 0.1 – 50 |
Humidifier | 0.9 – 3 |
Copier Toner | 0.5 – 15 |
Liquid Droplets | 0.5 – 5 |
Insecticide Dusts | 0.5 – 10 |
Anthrax | 1 – 5 |
Yeast Cells | 1 – 50 |
Carbon Black Dust | 0.2 – 10 |
Atmospheric Dust | 0.001 – 40 |
Smoldering or Flaming Cooking Oil | 0.03 – 0.9 |
Corn Starch | 0.1 – 0.8 |
Sea Salt | 0.035 – 0.5 |
Bacteria | 0.3 – 60 |
Bromine | 0.1 – 0.7 |
Lead | 0.1 – 0.7 |
Radioactive Fallout | 0.1 – 10 |
Rosin Smoke | 0.01 – 1 |
Combustion | 0.01 – 0.1 |
Smoke from Natural Materials | 0.01 – 0.1 |
Burning Wood | 0.2 – 3 |
Coal Flue Gas | 0.08 – 0.2 |
Oil Smoke | 0.03 – 1 |
Tobacco Smoke | 0.01 – 4 |
Viruses | 0.005 – 0.3 |
Typical Atmospheric Dust | 0.001 to 30 |
Sugars | 0.0008 – 0.005 |
Pesticides & Herbicides | 0.001 |
Carbon Dioxide | 0.00065 |
Oxygen | 0.0005 |
- one micron is one-millionth of a meter
Airborne particles
Airborne particles are solids suspended in the air.
Larger particles – larger then 100 μm
- terminal velocities > 0.5 m/s
- fall out quickly
- includes hail, snow, insect debris, room dust, soot aggregates, coarse sand, gravel, and sea spray
Medium-size particles – in the range 1 to 100 μm
- sedimentation velocities greater than 0.2 m/s
- settles out slowly
- includes fine ice crystals, pollen, hair, large bacteria, windblown dust, fly ash, coal dust, silt, fine sand, and small dust
Small particles – less than 1 μm
- falls slowly, take days to years to settle out of a quiet atmosphere. In a turbulent atmosphere they may never settle out
- can be washed out by water or rain
- includes viruses, small bacteria, metallurgical fumes, soot, oil smoke, tobacco smoke, clay, and fumes