Why Does My Central Air Have Two Filters? Know The Reason

Why Does My Central Air Have Two Filters? Know The Reason

Central air conditioners are the go-to choice for people with large homes or want cool spaces with multiple rooms. They use a duct system within the building to connect all the rooms and output consistent temperatures. 

The central conditioner also has filters that remove impurities and other unwanted particles from the air. So it provides better indoor air quality overall. All of the above are some of the reasons this system is highly favored across the U.S.

Now you may have noticed that your central air system has two filters, and you might be wondering if you need both.

Why Does My Central Air System Have Two Filters?

Firstly, note that you can have more than two filters. Multi-level houses are the most likely to have these. Why? For buildings with multiple rooms, it’s necessary to have various return ducts.

These return ducts are what suck in humid air within the room back into the central air system. The return ducts provide an escape for the air in the room so that the dry air supplied by the central air can come in. This function is what allows for a consistent temperature output.

Each of these return ducts must have air filters. In addition, homes or buildings due to human activity or components present in furniture or other materials usually have air mixed with other particles. 

So when the return duct is pulling in the air in the room, these particles move along with it. Therefore, these particles have to be trapped to keep the central air system clean and functional. The filters present in the return duct are responsible for trapping these particles.

Another reason why you could have two air filters is because you have a return duct and air handler. Air handlers help to control and circulate air. 

They have filters larger than those in the return ducts. This setup helps filters stay for long before they require replacement. The larger the filter, the more dirt it can take.

It could also be that you have multiple central air systems. Buildings with multiple floors usually have these types of setups. It means there will be numerous return ducts and air handlers which require their filters.

Now that we have seen why a central air can have two filters or more, let’s see some reasons to choose a central air conditioning system.

Reasons To Choose A Central Air Conditioning System

We have already established that this system is popular in the United States; let’s see why. 

First off, the central air conditioning system is quiet. The reason is that the system doesn’t have any significant power component inside, making it significantly more peaceful than most air conditioning systems.

A central air conditioning system frees up more space. A central air conditioning system uses ducts and vents; this means it gives you more space in your room and doesn’t mess with your home aesthetics.

We have seen why central air conditioning can be a good choice for many; let’s take a closer look at the air filters that come with them.

Types Of Air Filters

Air filters have a structure with tiny pores that do not allow pollutants and other harmful objects into your room’s air space. Air filters are classified mainly by the type of material used in making them and the structure.

Fiberglass air filters:

The fiberglass air filter has the fiberglass spread over a cardboard or metal frame. The fiberglass acts as the barrier for possible debris that might want to come in with the air. The fiberglass air filters don’t give the best protection but are considerably cheaper, hence why they are so popular.

High-efficiency particulate air filter:

This air filter has a high sensitivity because it can filter up to 99.97 percent of airborne particles. It provides a very high quality of air in the home or building. The difference is in how the fiber employed is used to create a very well-knit pattern.

However, the high-efficiency particulate air filter is costly and requires professional installation—all of these reasons why it might not be so necessary unless one has a medical condition.

Pleated air filter:

The pleated air filter design concept is similar to that of the fiberglass air filter. The difference is that it employs a polyester cloth. The cloth is arranged in an accordion shape and is more effective than flat filters. In addition, it is a long-lasting filter.

Reusable filter:

The reusable filter is made of cloth and can be washed and reused. It is relatively cheaper but has a low resistance to pollutants. You cannot use the reusable filter in areas with high rates of pollution. They have to be cleaned with caution to avoid damaging them; they should also be dried thoroughly.

We have looked at the types of air filters available; let’s look at how to check your filter, why, and when to change it.

Why You Should Check And Change Your Air Filter

The air filter, as we have elaborated, is an essential component of the central air system. Many major air system malfunctions are a result of dirty air filters. When the air filter is dirty, some of this dirt can get to other components causing them to malfunction.

A dirty air filter can also limit airflow into the system. As a result, it can lead to inconsistent temperature output. It can also cause the air handling fans to work harder than they were designed to, which leads to the fans wearing out quicker.

Having a dirty filter also means that you can no longer stop contaminants from entering your room. These contaminants can be potentially harmful to your health.

Again, the fact that some of these components have been overworking means they’ll consume more power. So, that means that your light bills may likely increase.  

It is advised that you check your air filter once every month. If the air filter has dirt, you should replace it or clean it if it is reusable. 

So if you are going to change your air filter, you need to know how to. So that’s what we will be looking at now.

How To Change Your Air Filter

Locate your air filter:

The first thing you have to do is locate your air filter. Achieving this can be problematic, depending on the type of system you have. For some, the air filter might be in the return duct. The larger the system, however, the more tedious it would be to find the filter.

When you are unsure, the best practice is to contact an HVAC (Heating Ventilation and Air Conditioning) expert. 

Another essential thing to figure out aside from locating the old air filter is to find a suitable replacement.

Find the suitable filter replacement:

The key to finding the right replacement is to know the size of the filter your system can accommodate. If you found the old air filter, the size is usually printed by the side. If you can’t find it, you should talk to an HVAC expert.

Also, you might want to get an air filter that can also take care of harmful contaminants aside from dust. In that case, you should look into high-efficiency particulate air filters. It is advisable when looking for high-efficiency particulate air filters; you should contact an HVAC expert.

After you have figured out the above, the next step is to know the steps involved in changing it.

Steps To Change Your Air Filter

Before you begin, put on a pair of gloves and a mask. The reason is to protect you from whatever contaminant that may have been trapped within the filter.

Switch off the system:

Shutting off the power protects you and the system. The first risk is that you can encounter live wires. The second is that while removing a dirty filter, dirt might fall off, and get sucked in.

Please take out the old filter:

When you have switched it off, locate and take out the old filter. It usually just needs to be slid out of its slot.

Check the condition of the old filter:

When you bring out the old filter, you want to check if the filter is covered in dust. If you hold it up and not much light comes through, you likely need to replace it or clean it, depending on whether or not you are using a reusable filter.

Insert the new filter:

This could also be the cleaned filter if you use a reusable filter. The filter comes with an arrow on the frame that shows the direction of airflow. It should point away from the return vent and towards the air handler when you slide it in place. And just like that, you have changed your air filter.


The central air system uses ducts to circulate and maintain the temperature within a room. A filter removes dust and other contaminants in the air that goes into the central air system. As a result, it provides a cleaner overall air environment. 

Some people using central air systems may have noticed that they have more than one air filter. The presence of many filters can result from multiple return ducts, an air handler, or just multiple central air systems in a multi-level building. These filters also help to constantly output temperature in every room. However, the inconsistent output can easily mean a filter is faulty.

About the author

Johnny is dedicated to providing useful information on commonly asked questions on the internet. He is thankful for your support ♥

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