Particle Sizes
A comprehensive reference tool for understanding particle sizes across different materials and contaminants. Convert between microns, meters, inches, and other units. Includes typical particle sizes for common materials like dust, pollen, bacteria, sand, and more.
Particle Size Unit Conversions
Key Relationships
- One micron (μm) is one-millionth of a meter
- 1 micron = 10⁻⁶ m
- 1 micron = 1000 nanometers (nm)
- 1 inch = 25,400 microns
- 1 micron = 1/25,400 inch
Eye Visibility
The human eye can generally see particles larger than 40 microns.
Airborne Particle Classification
Larger particles (>100 μm): Fall quickly, terminal velocities > 0.5 m/s
Medium-size particles (1-100 μm): Settle slowly, sedimentation velocities > 0.2 m/s
Small particles (<1 μm): Fall very slowly, can remain suspended for days to years
Hazardous Dust Categories
- Inhalable Dust: ≤100 microns (enters nose and mouth)
- Thoracic Dust/PM10: ≤10 microns (reaches the lungs)
- Respirable Dust/PM2.5: <5 microns (penetrates gas exchange region)