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What Happens if I Don’t Change My Air Filter?

If changing the air filters of your HVAC is the last thing on your mind, don’t worry; you aren’t the only one. Most of us only think about changing the filters once the HVAC system stops working or shows signs of damage and inefficiency. 

Usually, the biggest culprit of HVAC system failure is dust-filled air filters. 

So what happens when you don’t change your air filters in time? Keep reading to know!

How Air Filters Work

Air filters are usually made of paper or spun fiberglass and have a cardboard frame around them. These are placed in specialized slots in the HVAC system and prevent contaminants, dust, and other airborne particles from traveling through the air into your home or office. 

The filter also protects the sensitive parts of the HVAC from dust and other particles which may damage the unit over time.

Different grades and ratings of filters prevent different types of contaminants from flowing through the air. But most filters protect the HVAC from mold, dust, pollen, animal dander, hair, and bacteria.

Changing the Air Filters

Changing the air filters is often missed or something we only think about once our HVAC acts up. Remember that replacing the filters is not meant to keep your air pure; they are intended to protect the HVAC from dust and damage due to the air particles.

However, if you use high-grade air filters to protect against COVID-19 or other viruses and bacteria, such filters require a replacement much sooner than your regular ones.

The reason is that these filters allow less air to pass through. As a result, they are likely to trap more dust, dirt, debris, dander, and pollen than the regular filter. 

So there are more chances that mold and other problems will find their way to it.

How Often Should Air Filters Be Replaced?

Different types of filters require replacements at different points in time. Most filters are recommended to be changed every one to three months or once every thirty to sixty days. 

But the time could also depend on different situations and conditions. Here are some common situations and timelines for changing the air filters:

  • Change the air filter every sixty days if you have pets
  • A normal home without pets requires a filter change at least once every three months
  • If anyone in your home has a weakened immune system or other health conditions making them prone to allergies, change the air filter every 20 to 45 days.
  • In remote homes like farmhouses and other places you don’t visit often, you may replace the filter every six to twelve months.

What Happens When You Don’t Change the Air Filters

When the air filters are not changed, the first thing that happens is that dust and other particles start building up on them. As a result, they start getting clogged and allow less air to flow through. 

The blockage causes severe problems for the HVAC system and the health of the people in the facility.

Here are a few things you can expect if you ‘wait out’ on your air filters.

Higher Bills

When the filter becomes blocked, it allows less airflow. The whole HVAC system, in turn, has to work harder to allow more air through. Hence, it uses more energy and increases your electricity bills since it has to work longer than usual.

Inadequate Temperature Regulation

Blocked filters cause the system to work harder to generate the same temperatures. As a result, the system often fails to perform, and you don’t get the targeted temperatures in your home. 

So, during the peak temperatures, you’ll notice some rooms will be too warm while others may be too cold.

Health Conditions

When the filter doesn’t block out bacteria, mold, viruses, and dust, it causes health problems for the individuals breathing the contaminated air. Some of the effects you’ll immediately notice are:

  • Sore throat
  • Runny nose
  • Itchy eyes
  • Headaches and dizziness.

If the filters aren’t changed in time, and you continue to breathe in such air, you may develop heart disease, respiratory illness, and even certain cancers.

System Failure

The HVAC system has to work harder as the filter gets further clogged with time. When this happens for a certain time, the system fails and ultimately breaks down. 

Dust also jams the blower fan, valves, and other parts of the unit, further straining the system and causing higher energy consumption.

Frozen Evaporative Coils

The HVAC systems often have evaporative coils as an essential component. This part keeps the heat out of the air and keeps your home or office cool. However, the coil often freezes if the unit works harder to achieve efficiency. 

Moreover, since the blocked filter allows less air to flow through the unit, the coils may stop working, and you may have a complete system failure. 


If you have an efficient filter like the MERV filters in your HVAC, moisture and the darkness of the vent can lead to a major health issue; mold. 

Since a lot of circulated air goes through the system, mold, pollen, and other bacteria can spread faster if the filters are clogged. These allergens make people sick and cause the ‘Sick Building Syndrome.’


The HVAC system starts deteriorating with time if the issue is not addressed. If you ignore the need to change the filters, dust will settle in the ducts. It will affect all moving parts of the system and make it slow in filtering out the air.

The strain will affect each part of the unit and may cause either of these to wear out fast, ultimately affecting the life of the HVAC system.

How to Change the Filter

Changing the air filter is easy. It only takes about five minutes, can help your HVAC system enjoy a longer life, and will also reduce your electric bills. 

There are three steps to installing the filter

Step#1: Find

First, locate the placement slot of the filter. Some systems have it near the blowers, whereas others may have it by the furnace. 

Step #2: Select

Next, you need to find the right filter for your unit. Check the unit’s accurate size, the filter types compatible with the unit (MERV or HEPA?), etc. 

Step #3: Replace

Lastly, you need to replace the unit. First, turn off the power and then work on placing the filter. To replace, open the panel and take out the old filter. 

Look up the new filter’s arrow, and ensure it points away from the return air duct. Then, place the filter on the slot and secure the metal panel.


If you still need to, replace your air filters as soon as possible. But first, look at the types of filters used in the unit. 

If the blockage is beyond a DIY fix, contact the HVAC professionals. The team will visit and devise ways to completely recover your unit and advise on preventing future problems.