We may earn revenue from the product available on this page and participate in affiliate programme . Learn More ›
Q: I turned on my furnace for the first time this year, and it made the whole house smell musty. I checked the filter and found it caked with dust, so I replaced it with a new filter, and the indoor air is much fresher now. Are there any guidelines for how often a furnace filter should be changed?
A : As you name , a clean furnace filter makes a self-aggrandizing difference in strain quality . What ’s more , the fresher the filter , the more expeditiously your HVAC system runs , resulting in low muscularity bills . Filters are designed to trap dust and airborne particles as air is draw through the filter and into the furnace organisation .
The general rule is to change a furnace filter, which is usually located behind a return-air vent or in a slot on the furnace itself, at least once every 90 days.
Depending on your lifestyle and thetype of furnace filteryou choose , you may want to swap it out more often . Several factors should be regard when deciding how often to change a furnace filter , and many filter manufacturers recommend how often their product should be replaced .
Look for clues that it’s time for a new filter.
No two base are the same , so despite guidelines , you may need to change your furnace filter more often than your neighbor does . If your piece of furniture gravel dusty soon after housecleaning , the furnace filter could be clogged and is no longer effectively removing dust from the zephyr . You may also detect that your furnace runs more than usual . Take a peep at the filter : If it ’s gray and cover in dust and lint , it ’s time to replace it .
Fortunately, changing the filter is easy.
It involves loosening the nooky that admit the filter cover in spot if it ’s located behind a return - air vent or simply pulling the filter out from a slot if it ’s on the side of the furnace . The previous filter will be dirty , so have a large trash bag ready . Used furnace filters can be discarded along with your regular chalk . Then , insert the replacing filterinto the empty slot , and mark your calendar for the next substitution .
Replace the filter when the seasons change.
Marking your calendar every 90 days or trying to remember the last clock time you changed the filter can be challenging , so many furnace producer recommend surrogate at the head start of each new season . Yes , even in warm weather , when you ’re likely to be using your air conditioner . A clean filter is necessary to keep dust from being give suck through the HVAC system of rules , where it can gather on the line conditioner ’s interior coils and reduce the unit of measurement ’s efficiency .
Furnace use impacts how long a filter lasts.
If you exist in a temperate realm , such as the Southwest , you may only run your furnace a handful of times during winter , and the standard 90 - day rule of thumb might be perfect for you . northerly dwellers whose furnaces do n’t get a break for month , however , may require to alter their filter every 30 to 60 days , because more air is being drawn through the filter , and it will back up more quickly .
The denser the filter, the more frequently it should be changed.
filter are give aminimum efficiency reporting note value ( MERV ) , which ranges from 1 to 16 , although ratings of 6 through 12 are best for residential furnaces . Filters rate below 6 may not adequately block airborne particle , and filters with ratings gamey than 12 are designed for specialised use , such as in hospitals .
The higher the MERV rating , the good the filter is at forget airborne pollutants . In fact , filter with ratings of 11 or 12 will block up not only dust and favorite dander , but can also halt some types of microscopical viruses and fumes . This is because higher - rated filter have small muddle so fewer particulate matter can get through . Unfortunately , those smaller hole incline to clog more speedily than lower - rated filter with larger hole .
choked filters not only negatively impact the zephyr quality in a nursing home , but they also hale the furnace to ferment harder to absorb air into the system so they canshorten the useful life sentence of the furnace . Your furnace ’s owner ’s manual will specify the effective MERV military rank for your furnace , and in worldwide , filters with a MERV paygrade of 6 through 9 should be changed every 90 days , while those with a MERV paygrade of 10 through 12 should be change every 60 days .
Photo: Tom Fenenga for Bob Vila
Flat filters clog more quickly than pleated ones.
Most furnace filter come in two types , flat and pleated . Flat filters may clog more quickly because they have less surface sphere than do pleated filters . The deeper the pleats , the more Earth’s surface area a filter has and the more elbow room it has to collect airborne particles , so it may not congest as quickly as a flat filter . A categorical filter , such as theFlanders front gore filter , is designed to be change every 30 days . Due to their pleats , filters such as theHoneywell Ultra Efficiency filter , have more square inches of dust - trap quad , so they often require few changes — usually every 90 days .
Allergy sufferers will benefit from frequent filter changes.
In home base where a category fellow member has dust and/or preferred allergies , exchange the furnace filter frequently to check effective air caliber . Use a filter with a MERV valuation of 12 , such as theNordic gross filter , if your furnace can do by it . Because filters with high MERV ratings are denser , your furnace must do work hard to draw air through them and not all furnaces are powerful enough to do so . refer the possessor ’s manual for your furnace to determine the correct MERV filter military rating . As a general regulation to keep allergy suffers as well-situated as possible , change the furnace filter every 30 to 60 daytime .
Frequent filter changes are recommended for homes with pets.
Our beloved furry Friend play a vital role in our lives , but pet hackles — tiny flecks of pelt present in the fur and feathers of animals — can become airborne and choke the furnace filter . farseeing - hirsute ducky will disgorge more than short - haired change , but all will contribute to pet dander in the zephyr . Even if no one in the place is allergic , it ’s wise to change your furnace filter frequently , as often as every 30 day if you have multiple favorite , to keep the furnace functioning efficiently .
Remodeling projects play a role in filter durability.
All the sanding , scraping , and flooring installation involved with remodeling produce a lot of airborne junk and rubble . During a remodeling task , alter your furnace filter every 30 days , or even more frequently , to keep twist - touch on rubble from propagate through the household .
This Is the class for a Kitchen Renovation
Whether you ’re selling or staying , everyone can get something out of a kitchen update . Learn why we deal this renovation the Most Valuable Project of 2025 and how to appease on budget .
Photo: Tom Fenenga for Bob Vila
Photo: Tom Fenenga for Bob Vila
