Glossary · Health & indoor air
PM2.5 (fine particulate matter)
Also called: PM₂.₅ · fine particles · fine particulates · particulate matter
Fine, inhalable airborne particles 2.5 microns or smaller, from smoke, cooking, candles and outdoor pollution.
What it means
Indoor PM2.5 comes from cooking, smoking, candles, wood burning and outdoor air leaking in, especially during wildfire smoke. Range hoods vented outdoors, a better furnace filter (see MERV) and portable air cleaners lower it. Low-cost sensors give a rough reading in micrograms per cubic meter (µg/m³).
Why it matters in an audit
Tightening a home keeps outdoor smoke out but can trap particles made indoors, so ventilation and filtration should be part of the plan.
Typical numbers
Reference values with their sources. Your auditor’s report gives the figure for your own house.