Change a 1-inch fiberglass filter every 30 days, a 1-inch pleated filter every 60 to 90 days and a 4 to 5 inch media filter every 6 to 12 months. Look at it monthly. Shorten each interval for pets, allergies or smoke. We answer filter and airflow calls at (541) 461-2101 in Eugene and (503) 581-9982 in Salem.
How often should you change your air filter?
Change your air filter by type: every 30 days for 1-inch fiberglass, 60 to 90 days for 1-inch pleated and 6 to 12 months for media.
ENERGY STAR covers filter care in its maintenance checklist and tells you to inspect, clean or change the filter once a month in your central air conditioner, furnace or heat pump. A dirty filter can increase energy costs and damage your equipment, leading to early failure. That adds up. The intervals below follow PickHVAC’s schedule guide. They are general guidance. The instructions printed on your filter box win. We check the filter first on every weak-airflow call, so the interval matters to us as much as to you.
| Filter type | Normal home | Pets, allergies or smoke |
|---|---|---|
| 1-inch fiberglass (MERV 1 to 4) | 30 days | 20 to 30 days |
| 1-inch pleated (MERV 8 to 11) | 60 to 90 days | 30 to 60 days |
| 4 to 5 inch media (MERV 11 to 13) | 6 to 12 months | 3 to 6 months |
Read the right-hand column as one answer for all three conditions. A shedding dog, an asthmatic child or a smoker puts your home there. We hold any of those homes to the shorter number. The table gives a starting number. Your own filter gives the proof.
How often should you change a 4-inch media filter?
Change a 4-inch media filter every 6 to 12 months in a normal home, and every 3 to 6 months with pets, allergies or smoke.
Deep media holds more dust than a thin pleated filter, which is why it lasts longer between changes. Look at it each month anyway. The media loads at its own rate. If your furnace or air handler only has a 1-inch slot, you cannot simply drop a 4-inch filter in. It won’t fit. Our technicians install media cabinets when a home needs the extra depth, and we inspect the cabinet seal on a maintenance visit. How do you tell when any filter has run its course?
How do you know when it is time to change the filter?
Hold your filter up to a window or flashlight: light through the pleats means it has life left, and gray, matted media means change it now.
The check takes about a minute. Pull the filter, tilt it toward the light and look at the surface. EPA gives the same rule in its guide to air cleaners in the home: if your filters look heavily soiled whenever you change them, shorten the interval. On a preventative maintenance visit our technicians check filter fit and airflow, and we pull the filter and hold it to the light ourselves. You can repeat that look between visits. Your household and your weather change how fast the surface turns gray. Look often.
Do pets, allergies, smoke or pollen change how often you change it?
Yes. Pets, allergies and smoke push every interval to the shorter number in the right-hand column of the table above. We service homes with dogs, cats and smokers on that shorter schedule.
Two Oregon events matter most, spring pollen and fall wildfire smoke. During heavy smoke, the EPA says to replace the HVAC filter more often than the manufacturer recommends and to keep spare filters in the house. PickHVAC says to check it weekly. Weekly. Oregon’s wildfire smoke guidance from DEQ points homeowners to MERV 13 to 16 filters, which it says can remove 90% or more of the particles, and to set the system to recirculate when smoke is outside, if your equipment allows. After a smoke event we inspect the filter first, before we look at the blower.
Heating season counts too. A furnace or heat pump pulls house air through the same filter all winter. Your filter works year-round, not only in summer. After remodeling, sanding or any heavy dust, look at the filter once the work stops. Construction dust loads a filter quickly. No source we opened gives a number for that. So you get the look, not an interval. Where do you find the filter to look at it?
Where is your air filter, and how do you change it?
Your filter sits in a slot at the furnace or air handler cabinet, behind a large return grille on a wall or ceiling, or in both places. Check both.
Homes with the furnace or air handler in a garage, closet or crawlspace have the slot right where the return duct meets the blower. Others hold the filter behind the grille. Open the grille to reach it. Our technicians inspect the grille and the slot for gaps whenever we service the system.
We run the same five steps on a service visit, and you can run them too:
- Turn the system off at the thermostat.
- Slide out the old filter and note its size and airflow arrow direction.
- Check the slot for dust and wipe it.
- Slide in the new filter with the arrow toward the blower.
- Close the door or grille and restart the system.
Never run the system with no filter. Never bend or crush a filter to make it fit, which EPA warns against. One filter serves your furnace, AC and heat pump in a typical central system. Our technicians service furnaces and air handlers with slots in garages, closets and crawlspaces. Can’t find yours? We inspect the unit and show you the slot. Step two mentions size, so how do you read it?
How do you know what size air filter you need?
Read the size printed on the filter’s cardboard frame, as length by width by thickness, and buy that exact size. Not close. Exact.
A frame might read 20 x 25 x 1. That’s length, width and thickness in inches. The airflow arrow on the frame points toward the blower, away from the return. If the frame is blank, measure the slot and match the thickness. A 1-inch slot takes a 1-inch filter, and thickness changes the interval in the table. Our technicians check the size against your slot when you are not sure. What does a filter that stays in too long do to your system?
What happens if you never change your air filter?
Airflow drops, energy use rises and your equipment can fail early, according to ENERGY STAR. All three get worse with time.
A clogged filter lets less air reach the blower and the coil. Rooms get uneven. The blower works harder. In summer a starved coil can freeze. Weak vents are the usual first sign. Look at the filter before you look anywhere else. If a fresh filter does not fix them, see weak airflow from vents for what low airflow looks like, or why your AC blows warm air. The HVAC tune-up checklist shows what comes next. Our technicians inspect the blower and coil, and we clean what the filter let through. Which filter should go in the slot once it is clean?
Which MERV rating fits your system?
Use MERV 13, or the highest rating your system can accommodate, which is what EPA recommends if you replace the filter often.
MERV measures how well a filter catches particles. The EPA rates each MERV level by its minimum average capture at three particle sizes.
| MERV | Larger particles (3.0 to 10 micrometers) | Medium (1.0 to 3.0) | Smallest (0.30 to 1.0) |
|---|---|---|---|
| 1 to 4 | under 20% | not rated | not rated |
| 8 | 70% or more | 20% or more | not rated |
| 11 | 85% or more | 65% or more | 20% or more |
| 13 | 90% or more | 85% or more | 50% or more |
The EPA says most furnaces and HVAC systems can handle MERV 13 if you replace the filter frequently. We size the filter to your slot, not the slot to the filter. The catch is airflow. A denser filter resists air more. A thin 1-inch pleated MERV 13 clogs faster than a deep 4-inch media filter with far more surface area.
Run a simple check before you commit to MERV 13 in a 1-inch slot. Install it. Then look at it at 30 days. If it is already gray, or the vents blow weaker than before, drop to MERV 11 or move to a deeper media cabinet. We service 1-inch slots and media cabinets, and we test static pressure at the blower to settle it. And what will the filter cost you?
How much does an HVAC air filter cost?
A 1-inch filter costs $1 to $3 for fiberglass and $8 to $25 for pleated MERV 8 to 13, according to Filterbuy’s October 2025 retail guide.
| 1-inch filter | Retail price each |
|---|---|
| Fiberglass | $1 to $3 |
| Pleated MERV 8 | $8 to $12 |
| Pleated MERV 11 | $12 to $18 |
| Pleated MERV 13 | $15 to $25 |
Filterbuy is a filter retailer, so shop prices vary by brand and pack size. Run the schedule through those prices and the year looks like this. Fiberglass changed monthly is twelve filters, about $12 to $36. It catches the least. A MERV 8 changed every 60 to 90 days is four to six filters, about $32 to $72. Media filters of 4 to 5 inches vary more by cabinet size, so price yours against your exact slot. These are guide figures. We quote your actual parts after a visit.
Questions about filter changes
Can you change your air filter too often?
Changing early does not hurt the system. It only costs you a filter you did not need yet. Look at it monthly and change it when it is gray.
How often should you change an air filter in an apartment?
Use the same table, because filter type and your household set the schedule, not the building. Ask your property manager who owns the job, since the filter is not always handled for you.
Do furnaces, AC and heat pumps use the same filter?
In a typical central system, one filter serves all three, because the same blower moves air through it. A furnace or heat pump pulls air through it all winter too. We service all three, and we inspect the same filter on each.
Should you run the system with no filter while you wait for a new one?
No. Never run the system without a filter. Keep spares on hand so a swap is never a wait. The EPA covers spares in its smoke guidance too.
Does the brand of my furnace change the schedule?
No. The filter type and your home decide the interval, and we service Ruud and Rheem equipment under the same filter rule. Follow the instructions printed on your filter box.
When the filter is not the problem
A new filter that does not bring back airflow points to something else, such as a dirty blower wheel, a frozen coil or a duct problem. On a no-airflow call we check the filter, test static pressure at the blower, inspect the coil for ice and clean a dirty blower wheel. We quote any repair before the work starts. Both phone lines answer around the clock. Technicians dispatch from either one. Eugene, Springfield and Lane County homes can call (541) 461-2101. Salem, Keizer and Marion and Polk County homes can call (503) 581-9982. We have served the area since 1983 (Oregon CCB #47396), and our preventative maintenance visits cover filter fit and airflow. For upgrades beyond the filter, see how indoor air quality work improves comfort.
