Episode 82 explains respirable particle size and why understanding particle dimensions is essential for controlling exposure to airborne contaminants. Dr. Ayers uses size comparisons and practical examples to show how extremely small particles behave in the workplace and why they pose significant health risks.
Respirable particles are tiny airborne solids small enough to penetrate deep into the lungs, reaching the gas‑exchange region (the alveoli). The episode highlights that workers often underestimate how small these particles really are, so Dr. Ayers uses relatable size comparisons to make the concept concrete.
These particles are typically measured in micrometers (µm) and include:
PM10 — particles 10 microns and smaller
PM2.5 — particles 2.5 microns and smaller
Both are discussed in the episode as key exposure concerns.
Particle size determines:
How deeply particles enter the respiratory system PM2.5 can reach the alveoli, where gas exchange occurs.
How long particles stay airborne Smaller particles remain suspended far longer.
How easily they bypass defenses The body’s natural filters (nose hairs, mucus, upper airway) cannot stop the smallest particles.
What health effects they cause Fine particles are associated with chronic respiratory disease, cardiovascular stress, and long‑term health impacts.
The episode emphasizes that understanding size is the first step in selecting the right controls.
Dr. Ayers uses real‑world comparisons to help visualize particle size, showing how PM10 and PM2.5 relate to common materials and workplace exposures. These examples help supervisors explain the concept to workers who may not be familiar with microns or particulate science.
Because respirable particles are so small, effective controls must focus on:
Local exhaust ventilation
High‑efficiency filtration (HEPA)
Enclosures and isolation
Respiratory protection when engineering controls are insufficient
Good housekeeping to prevent re‑suspension
The episode reinforces that once particles become airborne, they are difficult to remove without engineered systems.
Leaders strengthen exposure control by:
Ensuring workers understand what “respirable” really means
Selecting controls based on particle size, not just chemical identity
Verifying ventilation and filtration systems are maintained
Training teams on how small particles behave and why PPE alone is not enough
Understanding respirable particle size helps leaders make better decisions about engineering controls, respiratory protection, and exposure monitoring.
