When to replace an air filter - Chicago Tribune
How to replace an air filter
An air filter on a home air conditioning and furnace unit requires changing on a regular basis. The filter is a key part of the performance of the unit to keep the cool or warm air flowing freely. A dirty filter may shorten the lifespan of the unit while causing more frequent needs for repairs.
When wondering whether your air conditioner filter requires replacement, you can rely on a few signs. You also can keep track of the time of the last installation of a filter and change it regularly, based on the calendar.
Why should you change an air filter?
As the air in a home or building moves through rooms and into the ductwork, it collects dust, pollen and other unwanted air pollutants. Running those particles inside a furnace can cause excessive wear to the parts of the furnace. Air filters can catch particulates in the air like dust, mold, pollen, soot and other microscopic particles.
The air filter sits just outside the furnace. The air moving through the home's ductwork passes through the filter before entering the furnace. Removing particles with the filter provides a few different benefits, including:
- Longer lifespan: Excessive particulates and dust passing through the ducts will reduce the performance and longevity of the entire HVAC unit.
- Better efficiency: With cleaner air moving through the ductwork, the furnace and air conditioner don't have to work as hard.
- Saving money: With better efficiency from the furnace and AC unit, you'll save on energy costs.
- Cleaner air: You may notice fewer health problems when you have cleaner air moving through your home.
Can I reuse an HVAC filter?
Do not reinstall an old disposable filter. If the filter has a reusable design, though, it's all right to reuse it. Some filters have a design made for cleaning in a washing machine. Others allow the homeowner to cut the washable fabric to fit for a custom-sized reusable filter.
To save some money, it may be tempting to try to clean a disposable filter after using it for several weeks. However, the design of the filter means it catches both dust and microscopic particles. You cannot fully clean the microscopic particles, which means a used disposable air filter will be far less effective than a new filter.
What happens if you change an air filter too early?
The only disadvantage to changing the home's air filter too early is that you'll spend extra money on filters.
Since you should never reuse an air filter, this means you should dispose of the air filter after using it. So if you replace the disposable filter too early, you'll end up spending more money over the long run.
However, for the longevity and performance of the HVAC unit, it's always better to change a furnace filter too early than too late.
When is it time to change an air filter?
There are a few different things to check when determining the right time to change the air filter.
Physical signs on the filter
You can always inspect the air filter by opening the filter compartment and looking at it. If it has a noticeable layer of dust on it, it's probably time to change it. Most filters consist of white materials, which makes it easier to see dark brown and grey dust.
Remember, air must be able to pass through the filter. Excessive dust will block the airflow. A smart thermostat may give you an alert when the filter's airflow is less than it should be. Additionally, if you notice any holes or tears in the filter, replace it immediately. This is far more common with a reusable air filter than with a disposable filter.
Excessive dust in the home or building
When you notice extra dust accumulating around air vents or elsewhere in the home, this is a sign of a poorly functioning air filter. If the filter is not removing dust and other contaminants, they will continue to pass through the air ducts, eventually accumulating on surfaces.
All buildings will have a gradual buildup of dust. But when the dust accumulation seems to occur faster than normal, it's time to check the filter.
Reaching the filter's effective lifespan
When you install a filter, the manufacturer should provide an estimated lifespan for the filter. Mark this date on your calendar so you have a reminder of when it's time to change the filter. Some thermostats allow you to set a filter-changing reminder based on a date.
If you have pets or if you live in an area where dust is frequently in the air, you may need to change the filter more frequently than the manufacturer recommends.
More expensive air filters may last three to six months, according to the manufacturer. Cheaper air filters may need changing each month.
How should you select a replacement air filter?
When looking to purchase an air filter for a furnace and HVAC system, it's important to match the required size and thickness. Each HVAC system requires certain dimensions in the filter. A filter that's too small won't catch the particulates and leave gaps for bad air to come through. A filter that's too big won't fit properly in the filter compartment, which could lead to air leakage and wasted energy for the system.
Some units will not operate properly with the wrong size of filter in place. You may see an error message on the digital thermostat. Some HVAC units simply won't run after inserting the wrong size of filter.
Once you have the right size selected, you then can select the MERV rating you want to use. A higher number in the MERV rating will catch smaller particles than a filter with a lower MERV number. When a MERV rating is high, rest assured that your filter is catching as many particles as possible.
Some common MERV filter ratings and products include:
- MERV 5: Filtrete Furnace Air Filter, which catches pollen, dust and dander.
- MERV 8: FilterBuy Replacement Air Filter, which catches pollen, dust, dander and dust mites.
- MERV 11: AIRx Pleated Air Filter, which catches pollen, dust, dander, mold and dust mites.
- MERV 13: Aerostar Max Air Filter, which catches pollen, smoke, dust, dander, mold, bacteria and dust mites.
- MERV 16: Lennox Carbon Healthy Air Filter, which catches pollen, smoke, dust, dander, mold, bacteria, virus carriers and dust mites.
Kyle Schurman is a writer for BestReviews. BestReviews is a product review company with a singular mission: to help simplify your purchasing decisions and save you time and money.
BestReviews spends thousands of hours researching, analyzing and testing products to recommend the best picks for most consumers. BestReviews and its newspaper partners may earn a commission if you purchase a product through one of our links.
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