Guide
What is PM2.5, and why does it matter at home?
A plain-English guide to the smallest, most troublesome particles in your air.
Quick answer
PM2.5 is airborne particulate matter 2.5 microns or smaller, small enough that about 30 particles fit across a human hair. It gets past the nose and throat into the lungs. Indoors it comes from outdoor smoke and exhaust leaking in, plus cooking, candles and fireplaces. MERV 13 to MERV 16 and HEPA-grade whole-home filters capture it.
Small enough to reach your lungs
PM2.5 sounds technical, but it’s just a way of describing tiny particles in the air. Because they’re so small, your nose and throat can’t filter them out. They travel deep into your lungs, and the finest particles can pass into the bloodstream.
It’s an indoor problem too
Every time your home exchanges air through leaks, open doors, bath fans or your HVAC system, outdoor air comes in. That means wildfire smoke, car exhaust and industrial pollution can end up in your living room. Indoor sources like cooking, candles and fireplaces add even more.
Who should care most
- Kids: developing lungs, and more air breathed per pound of body weight than adults
- Older adults: more likely to have heart or breathing conditions that PM2.5 can worsen
- Anyone with asthma, allergies or heart conditions: fine particles are a known trigger
- Expectant mothers: studies link PM2.5 exposure to pregnancy outcomes
- Active people: exercise at home means deeper breaths
How to reduce PM2.5 at home
- Upgrade from a 1-inch furnace filter to a MERV 13 or better media cabinet
- Choose MERV 16 or HEPA-grade (like NovusAer) for smoke, allergies or asthma
- Run your HVAC fan more often during smoke events so air passes the filter
- Use kitchen exhaust when cooking and limit candles and wood burning
- Keep the system clean and change media on schedule
| Particle | Typical size | Stopped by |
|---|---|---|
| Human hair (width) | 50–70 µm | n/a (reference) |
| Pollen | 10–100 µm | MERV 8 and up |
| Dust mite debris | 10–40 µm | MERV 8 and up |
| Mold spores | 3–30 µm | MERV 11 and up; UV for growth on coils |
| Pet dander | 0.5–10 µm | MERV 11–13 and up |
| PM2.5 (smoke, exhaust) | 2.5 µm and smaller | MERV 13–16, HEPA-grade |
| Bacteria | 0.3–10 µm | MERV 16 / HEPA-grade; UV and PHI treatment |
| Viruses | 0.02–0.3 µm | Partly MERV 16 / HEPA-grade; UV and PHI treatment |
Related
FAQ
Frequently asked questions
What does PM2.5 mean?
Particulate matter 2.5 micrometers in diameter or smaller. About 30 PM2.5 particles fit across the width of a human hair.
Where does PM2.5 in my home come from?
Outdoors: wildfire smoke, vehicle exhaust and industrial pollution that enter through leaks, doors, fans and your HVAC system. Indoors: cooking, candles and fireplaces.
What filter captures PM2.5?
MERV 13 captures a meaningful share; MERV 16 and HEPA-grade media such as NovusAer capture much more. Filtration works best when the system runs regularly so air passes through it often.
Ready to breathe cleaner air at home?
Book a free in-home air assessment. We inspect your HVAC system, look at your family’s needs, and give you a clear, installed price before any work starts.
Or call 801-823-1399 · All prices include professional installation by certified HVAC installers.