When to Change Air Filters: 5 Major Signs You Need to Change Your A/C Filter

Make sure your A/C system is working to its full potential and know when to change air filters. Here are 5 major signs you need to change your A/C filter. More than 50 million people across the United States suffer from various allergies every year. For many of these people, typical indoor air at home or the office can turn deadly if the air conditioning (A/C) unit isn’t functioning correctly. To avoid adding more allergens into the indoor air, you need to keep replacing the filters.

Here are five clear signs on when to change air filters to maintain high indoor air quality.

Signs to Know When to Change Air Filters for Your A/C

The type of system you have in your house determines if you use a single or multiple air filters. If you’re using fiberglass filters, you need to change them every 30 days. For more expensive pleated filters, six months is the most they should go before replacement.

Here are some definite signs to look out for at every inspection, to determine if it's time to change the air filters:

1. There Is More Dust Near Vents

If upon a cursory inspection of your system, you find dust near the vents, then it may be time for filter replacement. To confirm this is the case, you can run two handy tests.

For the first test, you will need to compare the amount of dust on the surfaces near the vents and those far away.

If you notice that there is more dust on those surfaces near the vents than those far away, then it’s a clear indicator that air filter replacement is imminent.

The second handy test you can conduct to determine if your air filter needs to go is the ‘white sheet test.’ Take a clean white sheet and hang it five inches from a filter. After one hour, inspect the white sheet.

If the previously white sheet has turned grey, then you have a filthy filter that needs replacing. The deeper the grey color on the sheet, the dirtier the state of the air filter.

2. Your Energy Bills Have Increased

Whenever your energy bill starts to shoot up, there are several things you need to check. It could be that you have a faulty appliance. At other times, your crawl space encapsulation may not be as effective. When this is the case, the crawl space will be letting in the air with a higher level of impurities, which makes your A/C work much harder and consume more power.

One other common reason for higher energy bills is usually a poorly functioning A/C unit.

The moment you suspect it could be your A/C (or after you have ruled out all other possible causes, you need to inspect the vents. If you find there is extra dirt on them, then it means your filters are no longer functioning as well and need replacement.

3. Your Air Conditioning Unit Heats up Abnormally

The level of dust near the filters is not the only way to tell if your A/C unit is operating at optimal levels. How hot your unit runs is a reliable indicator of whether your air filters are enabling the system to work without straining.

A clogged air filter will force the rest of the unit to run harder to hit the same kind of service levels as before. As the A/C tries to adjust in this manner, its mechanical parts begin to heat up abnormally.

If you want to confirm this, you can carefully touch the back of the unit to feel it is hotter than usual. When you have extremely dirty air filters, you can feel warm air coming out from the back of the unit.

You should swap the air filters to avoid reducing the machine’s lifetime due to overworking it.

4. The Air Isn't as Cool or Warm Anymore

When your A/C unit no longer blows warm or cold enough air as it used to, the first culprit you should check is the air filter.

A filthy air filter will hamper the flow of the cold or warm air emanating from the unit.

Unless you have other technical difficulties with your A/C, then replacing the air filters will often do the trick.

5. You Suffer More Allergen Attacks

The air inside your home or office contains dust, pollen, and pet dander among other allergens.

When dust particles, pollen, or pet dander in the air reach the A/C vents, they cling to the air filter. Over time, these filters become clogged with such pollutants. As long as your unit is functioning correctly, you will manage the level of allergens in the indoor air.

However, when your air filters are too saturated with a build-up of allergens, your unit will start blowing out polluted air. The levels of allergens in the indoor air increase inordinately, which then begins to affect people sensitive to allergies, causing more frequent attacks.

As such, you must maintain a regular inspection routine for your air filters to avoid allergen saturation.

How to Determine the Efficacy of an Air Filter Model

Air filters run on a minimum efficiency reporting value (MERV) rating. The MERV rating scale runs from one to 20, with the number reflecting the degree of efficiency in filtering out particulates.

As such, a higher MERV rating means that the filter can get rid of more air pollutants than that with a lower MERV rating.

More specifically, a rating between one and four indicates low efficiency. Such filters are made to protect the A/C system but not necessarily improve the air quality.

A MERV rating between 5 and 13 shows that the air filter is moderately efficient. If you use such a filter, it can remove a degree of small to large particulates excluding dust mites.

Top-notch air filters have a MERV rating of 14 to 16. These filters are highly efficient and can eliminate particulates that are as small as 0.3 microns.

Improve Your Indoor Air Quality

The air inside your home or office contains allergens that can trigger reactions among sensitive people. Furthermore, if the indoor air contains dangerous things like mold spores, you may be risking your health. Therefore, it is essential to know when to change air filters to avoid the build-up of allergens and other pollutants.

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