7 Reasons Your Filter Isn’t Improving Your Indoor Air Quality

Although indoor air may appear pure and unspoiled, it is, in fact, saturated with minuscule particles. These particles, such as dander, can often be seen drifting visibly in direct sunlight. And because they are only a few micrometers in length, they can effortlessly enter narrow passageways. Unwittingly, we inhale them, and these indoor air pollutants penetrate deep into our lungs. Prolonged exposure to a high concentration of pollutants in the air can have negative impacts on our health. Fortunately, we can enhance indoor air quality by employing filters that capture particulate matter. While heating systems and air conditioners come equipped with filters, they may not effectively capture all pollutants. In this case, it is necessary to identify the reason why your HVAC filter is not improving indoor air quality.

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7 Reasons Your Filter Is Not Improving Your Indoor Air Quality

The following reasons may be causing an HVAC filter to not operate at its maximum capacity:

1. No Filter

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Have you recently relocated to a new residence? It is reasonable to expect that the HVAC system is functioning correctly and that all components are in place. However, if there is an abundance of dust and allergens circulating in the air, it’s cause for concern. You should check to see if the HVAC air filter is present. There are instances where the filter slot is left empty, allowing unfiltered air to pass through. Perhaps the previous owner neglected to replace the filter, or they found it difficult to access and gave up. This can lead to the rapid accumulation of dirt and dust in the ducts, coils, and blowers.

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2. HVAC Filter Installed Incorrectly

It is crucial to not only have an HVAC filter but also to install it correctly. Simply purchasing a high-quality air filter is not enough when it is not installed properly. Even a tiny gap can allow dirty air to bypass the filter. This gap renders it ineffective at blocking particulate matter and leaving you with poor indoor air quality. Replacing the filter, as the manufacturer recommends, won’t make a difference if the installation isn’t perfect. Homeowners may not realize they’re making mistakes, but HVAC technicians will likely identify any issues during maintenance checks.

3. Not Enough HVAC System Runtime

air conditioning vent with ac unit that is blocked

Air filters are static installations that require air to flow from one side to the other in order to function properly. This means that the HVAC system must run for a sufficient amount of time to force enough air through the filters. HVAC systems that are too large can cause issues because they reach the desired temperature too quickly and shut off prematurely. To avoid improper sizing, it is vital to have a contractor determine your exact heating and cooling needs. Changing the fan settings from “AUTO” to “ON” can also extend the system’s run time. However, doing so will increase your energy consumption. If you are still dissatisfied with the air quality, consider using a standalone air filter to address this issue. Consult with an HVAC contractor to learn more about ways to improve indoor air quality.

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4. Not Enough HVAC Airflow

In some instances, the runtime may be acceptable, but the airflow is constrained, resulting in decreased filtration capacity. The primary cause of this issue is often undersized return ducts. Another common cause is clogged filters, which can occur when individuals neglect to replace their HVAC filters. If the surface of the filter becomes too dirty, the air will struggle to pass through, leading to increased air pressure and decreased airflow. This can also have a negative impact on the system’s efficiency. To ensure that the filters effectively trap particles while allowing clean air to flow freely, it is essential to replace them regularly.

5. MERV Rating Is Too Low

The acronym MERV stands for Minimum Efficiency Reporting Value and is a critical specification for air filters. While low MERV-rated units may be more affordable, they are less effective at capturing air pollutants. High MERV-rated filters can be expensive, but they provide outstanding filtration performance. So, when searching for new air filters, it’s crucial to avoid immediately choosing the lowest-priced model and instead evaluate the value for money. Investing a little more in a higher-rated MERV filter could pay off by promoting cleaner air and reducing the likelihood of respiratory problems when spending time indoors. Be sure to consult with an HVAC technician about which MERV rating is compatible with your type of system.


6. Failing To Filter Outdoor Air For Mechanical Ventilation

The quality of HVAC systems is highly dependent on their installation. Even if a unit comes from a reputable brand, it won’t make a difference if the design or installation is flawed. One common error is connecting the outdoor air duct to the return side of the system, which bypasses the air filter. While this is rare, a skilled technician can quickly identify this mistake. Although it may be frustrating to discover, you’ll have a better understanding of the problem and can take appropriate action to rectify it.

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7. Filter Is In The Wrong Location

To determine the appropriate position for the air filter, it is crucial to comprehend the functioning of the existing HVAC system and the direction of air movement. Although the placement may seem unimportant, errors can occur. Inadequate or non-optimal placement can lead to subpar filter efficiency. Even the most advanced models may fail to deliver the expected results if they are situated in an unsuitable location.



The air filter plays a crucial role in maintaining indoor air quality. If your family frequently experiences sneezing, coughing, or respiratory problems, consider checking the HVAC filter. It could be displaying any of the problems mentioned earlier. To prevent errors, choose the appropriate type and ensure proper installation. If you face any issues, promptly seek the assistance of a skilled HVAC contractor. They can conduct a comprehensive system evaluation and upkeep to remedy any problems. You will notice an instant improvement in air quality.

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At Miller Oil Company, we take pride in offering exceptional heating and cooling services in Hartford County, Connecticut, and surrounding areas. Our team comprises certified and highly-skilled technicians with the expertise to perform top-notch HVAC tune-ups, repairs, installations, and replacements.

We believe in providing the most cost-effective heating and cooling services without compromising quality. Our comprehensive maintenance services are designed to enhance your comfort, boost energy efficiency, and reduce home energy expenses. In the event of an HVAC breakdown or replacement, we can suggest the most suitable option for your home that meets your budget requirements. Our work is backed by a guarantee to ensure your ultimate satisfaction.

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