The rule of thumb is to change your furnace air filter at least every three months. But there are other factors that determine when you should change your air filter. Obviously, if the filter looks dirty, you should swap it out. But what if it looks relatively clean? Hair, pollen, and airborne particulates aren’t always visible to the human eye. So, you can’t always trust your eyesight to help you determine whether you need a new filter.
Even if the filter seems fine, it may only be working at around 50%. That could strain your HVAC system and reduce the air quality in your home. To determine whether your furnace air filter needs a replacement, ask yourself the following questions.
Do you have allergies?
If you or someone in your family suffers from allergies, you should swap out your filter more often. The dirtier an air filter gets, the less effective it is at trapping allergens within your home. Check the manufacturer’s recommendations and cut the change time in half to ensure that your air quality is optimal. You should also monitor pollen counts and keep your windows and doors shut during peak times. This way, fewer allergens will enter your home and find their way into your HVAC system.
Do you have pets?
If you have cats or dogs, you will want to change your air filter more often. Pet hair and dander can build up in a home and find their way into your HVAC system. A high-quality filter is essential for protecting your system in addition to removing these particles from the air you breathe. As with pollen, if the filter gets dirty or clogged, it can’t trap pet hair and dander as efficiently. If you have pets, change your filters more often. If you have several pets, consider investing in an air purifier to take some of the burden off your air filter.
What type of furnace filter do you have?
Filters vary in several key ways, depending on the system and price. Fortunately, they almost always include factory recommendations on how often you should change them. Some will require a replacement every month, while others can go as long as six months. In most cases, you’ll need to change cheaper air filters more frequently, because they are either thinner or comprised of less effective material. You can determine the quality of a filter by looking at the minimum efficiency reporting value, or MERV, and the dimensions on the long side of the filter.
- MERV 1-4 (decent): These filters can pick up particles like pollen and regular standing dust, about 10 microns or larger.
- MERV 5-8 (good): These filters are better at catching small particles such as mold spores, hair spray, dust mites, and animal dander, typically 3–10 microns in size.
- MERV 8+ (better): These air filters can remove very small pollutants including particles like humidifier dust, auto emissions and legionella, which are 1–3 microns.
Ultimately, you’re better off spending a little extra on a quality filter that has some staying power.
In addition to the previously mentioned factors, there are a few other things that can influence how often you should change a furnace filter.
- You can expect your filter to clog up faster if you have lots of guests or several people living in your home.
- If you smoke, leave your thermostat at on instead of auto.
- If you tend to leave your doors and windows open, your filters won’t last as long. You should also consider changing out your filter more frequently during the peak winter months between December and February.
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