How Often Should You Change Your Air Filter?

Learn how often should you change your air filter depending on factors such as location of your home, pets at home and age of your system & equipment.

How Often Should You Change Your Air Filter?

Most air filter manufacturers and HVAC companies recommend changing your air filter every 90 days or 3 months. This may vary depending on the location of your home, if you have pets, and the age of your system and equipment. The only way to be sure how often your air filter should be changed is to do a visual inspection of the filter every month. After a few months, you'll get an idea of how quickly it gets dirty.

You may need to re-evaluate if you have a new pet or if the outdoor air quality has been poor. The ideal is to change the air filter every three months, however, there are certain factors to consider when determining when to change an old filter. An HVAC filter will only last one to three months on average, so you need to keep track of the date you installed them. If you wait too long to change the filter, indoor air quality will suffer.

A general rule of thumb for pleated air filters (such as those manufactured by FilterBuy) is to replace the filter every 90 days. As the filter traps more dirt, dust and allergens from the air, its efficiency decreases. Let's explore each of these factors in more detail. The filter collects dust and debris only when the system is in operation.

The longer it works, the faster the filter picks up dirt. During a cold and bitter Minnesota winter, the oven filter will need to be changed more often than during a mild Missouri winter. On the other hand, you will have to change the filter more often during a hot and humid Missouri summer than during the summer in Minnesota. Remember that a filter also gets dirty during AC mode.

Do you find pet hair in the filter of your oven? The hair fibers of dogs, cats, rabbits and other mammals are large compared to the dust and dirt that are normally trapped by the filter. That means they clog the filter and block airflow pretty quickly. The more important clean air is, the more often the filter needs to be cleaned or changed. A coarse media filter, MERV 11 or higher, or an electronic air filter are a better choice when anyone in the household has asthma, severe allergies, or forced breathing for any reason. The air will be cleaner than using a basic fiberglass air filter.

You may also want to consider an air purifier for your system. Cheap fiberglass filters require a change less often than pleated filters. Coarse media filters trap more and smaller dust particles, so they obviously get clogged faster. Fine fiberglass filters don't trap as much dirt and debris, so they don't clog up as quickly. The good news is that some of those filters can be cleaned with a nylon brush and put them back in the oven or air conditioner instead of replacing them. Cleaning should be done outside or in a garage to keep dust and dirt out of your home.

If you brush off dirt instead of replacing the media filter, be sure to change the filter after two or three cleanings. Over time, brush cleaning will not remove enough deeply embedded dirt and debris. In larger houses, more air flows through the filter than in smaller houses. As air carries dust, pet hair and other debris, the filter gets dirty more quickly in a system that serves a large house. Some thermostats have an Auto and Fan option setting. In automatic mode, the fan works only when the system is heating or conditioning the air in your home.

In fan mode, it works all the time until you turn it off. The longer the system works, even if it is not heating or air conditioning, the faster the filter will get dirty and will need to be changed. Running the fan requires electricity, so you'll see an increase in your electricity bill. Second, basement air is usually more humid than air above which makes you uncomfortable in summer. Humidity makes you uncomfortable in summer, so you'll have to lower the thermostat setting to remove moisture which causes your air conditioner to work more often resulting in higher electricity costs. Follow these steps to know when to change your air filter: Know your system and its sounds so you know what noises indicate a problem; look for signs of wheezing even when the filter is clean; it will get worse when it's dirty; clean with a nylon brush outside or in a garage; replace after two or three cleanings; consider an electronic or media air filter if anyone has asthma or severe allergies; use an air purifier for extra protection.