12 min read · Maintenance
The short answer
| Filter thickness | Typical change interval |
|---|---|
| 1" pleated | Every 1–3 months |
| 2" pleated | Every 3–4 months |
| 4"–5" media | Every 6–12 months |
Then adjust for your home using the factors below. When in doubt, pull the filter out and look: if you can't see light through it, or the surface is grey and caked, replace it.
What shortens filter life
- Pets: one dog or cat – cut the interval by about a third. Two or more, or heavy shedders – roughly halve it.
- Allergies or asthma in the home: change more often so the filter keeps working at full efficiency.
- Wildfire smoke: smoke can load a filter in days. Check weekly during smoke events and replace when it looks dark.
- Renovations and new construction: drywall dust clogs filters fast. Check every 2–3 weeks during and after work.
- Smoking or wood-burning indoors: change monthly.
- Fan set to "on" all the time: more air through the filter means it fills faster – but also means cleaner air.
- Big home or busy household: more people, more dust.
Canadian seasons
- Winter (heating): the furnace runs for hours a day with windows shut. Check monthly.
- Spring: tree pollen peaks. Good time for a fresh filter.
- Summer: if you have central air, the same filter protects your AC coil. Grass pollen and wildfire smoke peak.
- Fall: ragweed season, then the heating season starts. Replace before you fire up the furnace.
A simple habit: replace at the start of each season, and check monthly in between.
Why it matters
- Air quality: a loaded filter can bypass air around its edges and stops doing its job.
- Energy: a clogged filter makes the blower work harder, which costs money and wears the motor.
- Equipment: restricted airflow can overheat the heat exchanger or freeze the AC coil – expensive repairs.
- Comfort: weak airflow means cold and hot spots.
Commercial buildings
Offices, schools, long-term care homes and industrial sites usually change filters on a schedule set by the building's maintenance plan, often quarterly for pleated filters and annually for final filters, or by pressure drop readings. Property managers can set up scheduled bulk deliveries so filters arrive before each change-out.
Tips
- Write the install date on the filter frame.
- Set a phone reminder or subscribe to a delivery schedule.
- Keep one spare on hand so you're never stuck with a dirty filter.
- Make sure the airflow arrow points toward the furnace.
Stock up and save. Multi-packs of pleated filters are made in Brampton, Ontario. Managing several units or buildings? Request a bulk quote.