How often you need to replace the air filters may be on the following:
- Air filter style
- Total indoor air quality
- Quantity of pets
- Household size
- Air pollution levels and construction near the residence
- Your MERV Rating
For standard 1"–3" air filters, manufacturers usually instruct you to replace them every 30–90 days. If someone in your family suffers from mild to moderate allergies, you could put in a better air filter or change them even more often.
The shortest answer to "how frequently do I have to replace the air filter?":
If you don't have a smoker or pets in the home, and your filter is the commonly sold 1" filter with a MERV rating of 4, you should be able to wait up to 90 days before replacing it.
What air filter styles last longer?
A few air filters are designed to survive up to six months, while others have to be swapped monthly. The denser the air filter, the longer it can last. In most cases, you can look at the thickness of the filter versus the brand. You also need to look at the MERV Rating.
The MERV Rating is a scale that stretches from 1-20 and assesses how well an air filter should eliminate particles from the air. The better the MERV Rating, the smaller the particle that could be captured by the air filter.
While a filter with a higher MERV Rating will last longer, it may also hamper the ventilation in your home. And you will need to replace the filter more regularly. And if you acquire an older piece of equipment, plan to change the filter more regularly to extend the life of your filter.
How regularly do I have to exchange my air filter based on thickness?
The lifespan of an air filter also depends on its thickness. A 1" filter will have to be exchanged more frequently compared to a 4" filter.
- A 1" pleated air filter should be changed every 30-60 days.
- A 2" pleated air filter should be exchanged every 90 days.
- A 3” pleated air filter ought to be switched every 120 days.
- A 4" pleated air filter must be swapped out every 6 months.
- A 5” or 6" pleated air filter should be changed out every 9-12 months.
One of the advantages of denser filters is not only do they survive longer, but they also have a higher MERV Rating. This means they should do a better job of filtering out the particles within your home. They also generate less air resistance, which can help an HVAC system work more proficiently and reduce strain on components such as the blower motor.
If you own a whole-house air purifier, you will also need to exchange the filters more frequently.
How often should I change my air filter if I own a dog or cat?
If you have pets, you might need to change out your air filter more frequently. Pet hair and dander can quickly clog an air filter and reduce its effectiveness. For each shedding dog you own, expect to exchange the filter a month sooner than you would with a home without pets. The same applies to cats, although they don't shed as often as dogs. If you have a hypoallergenic or non-shedding dog or cat, you might not have to switch out your air filter as frequently.
Although a good rule of thumb, you might want to examine the air filter more frequently to determine if it needs to be exchanged. Dogs tend not to shed the same amount all year. They shed more in the spring and fall when they are blowing their coat. Take a look at the air filter monthly and exchange it when it looks clogged.
Here are averages that might help you understand how often you should install a new air filter at your residence:
- Vacation house or an individual occupant and no pets or allergies: every 6–12 months
- Ordinary suburban home without pets: every 3 months
- A single dog or cat: every 2 months
- More than one pet or if someone has allergies: 20–45 days