How Often Should You Change Your Furnace Filter?
Change a standard 1" pleated furnace filter every 60–90 days. Replace it monthly if you have pets, allergies, or during wildfire smoke season. Thicker 2" filters last 2–3 months, 4" filters last 6 months, and 5" media filters last up to 12 months.
Furnace filter replacement schedule
| Filter depth | Typical interval | With pets / allergies |
|---|---|---|
| 1 inch | 60–90 days | 30–45 days |
| 2 inch | 60–90 days | 45–60 days |
| 4 inch | 6 months | 3–4 months |
| 5 inch | 9–12 months | 6 months |
What affects how often you change it?
- Pets: Dander and hair load a filter much faster — shorten intervals by roughly half.
- Allergies and asthma: More frequent changes keep capture efficiency high.
- Wildfire smoke: During smoke events, inspect monthly and replace as soon as the media looks grey.
- Renovations and dust: Construction dust can clog a filter in days.
- Runtime: Homes that run the fan continuously cycle more air through the filter.
Signs your filter needs changing now
- The media is visibly grey or matted with dust.
- Airflow from vents feels weaker than usual.
- Dust is settling on surfaces faster.
- Heating or cooling cycles run longer.
- Energy bills creep up without a weather change.
Frequently Asked Questions
Is it bad to leave a furnace filter in too long?
Yes. A clogged filter restricts airflow, forcing the blower to work harder, raising energy bills, reducing comfort, and in severe cases overheating the furnace or freezing the AC coil. A dirty filter also stops capturing particles effectively.
Can I just clean my furnace filter instead of replacing it?
Only washable/electrostatic filters are designed to be cleaned and reused. Standard pleated and fiberglass filters are disposable and must be replaced — washing them damages the media.
Should I change the filter more often in winter?
If your furnace runs heavily through a Canadian winter, yes — more runtime means more air filtered and faster loading. Check it monthly during peak heating season.
Recommended Products
- Pleated Air Filters
- Save Favourite Sizes & Reorder — Set up recurring orders
- Custom-Size Air Filters
Need help choosing the right filter?
Talk to our Canadian air filtration team. Call 1-888-973-3635 or request a quote.