PM2.5 vs PM10: What's the difference?

Particulate matter (PM) is microscopic solid or liquid debris suspended in the air. The number after “PM” refers to particle diameter in microns. The two you will see most often are PM2.5 and PM10.

PM10 — coarse particles

PM10 includes particles up to 10 microns wide. Common sources include dust, pollen, mould spores, and road grit stirred up by traffic. These particles are large enough that your nose and upper airways often filter them before they reach deep lung tissue.

PM2.5 — fine particles

PM2.5 particles are 2.5 microns or smaller — roughly thirty times thinner than a human hair. They come from combustion: vehicle exhaust, wood fires, industrial processes, and wildfire smoke. Because they are so small, they can penetrate deep into the lungs and even enter the bloodstream.

Why PM2.5 matters more for health

Long-term exposure to elevated PM2.5 is linked to heart disease, stroke, and respiratory illness. Short spikes can trigger asthma attacks and reduce lung function in sensitive people. That is why many air quality apps emphasise PM2.5 even when PM10 is also reported.

What you can do

• On high PM2.5 days, postpone vigorous outdoor exercise.
• Keep windows closed when smoke or traffic pollution is elevated.
• Use a well-fitted N95 or FFP2 mask during exceptional smoke events if you must be outside.

On Aether, pollutant cards show each reading against WHO guideline levels so you can see how far above typical limits the air is.