Air Filters 101: What They Do and How They Work

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Like many, you may take your indoor air quality for granted. You assume that the air you breathe inside your home or workplace is clean and safe. This is not always the case. Dust, pollen, pet dander, and other airborne contaminants may lower indoor air quality and harm your health. This is where air filters come in. This article takes a closer look at air filters – what they do and how they function.

What is an Air Filters?

An air filter is a device that traps particles and contaminants from the air they pass through. They’re widely used in applications like HVAC systems or air purifiers to guarantee clean, healthy air for breathing. Air filters work by trapping these airborne particles – like dust particles, pollen, bacteria – in a filter media, allowing only clean air to pass through.

What Types of Air Filters Exist?

Various air filters are available on the market, each offering their own advantages and characteristics. Here are common examples:

1. Fiberglass Air Filters

Fiberglass air filters are the most common in residential HVAC systems. Constructed from layered fiberglass fibers, they trap large particles like dust and dirt. Despite being relatively inexpensive, these filters only capture a small fraction of airborne particles. To add insult to injury, their MERV (Minimum Efficiency Reporting Value) rating suggests they may only capture some particles.

2. Pleated Air Filters

Pleated air filters offer an improvement over fiberglass filters, boasting a higher MERV rating and the ability to capture smaller particles like pet dander or pollen. Made of synthetic fibers that fold into pleats, pleated filters create more surface area for air to pass through, making them more expensive but more effective at trapping airborne particles. While more expensive, pleated filters offer better efficiency at trapping particles than their fiberglass counterparts.

3. High-Efficiency Particulate Air (HEPA) Filters

HEPA filters are the gold standard, capable of trapping 99.97% of particles that measure 0.3 microns or larger in size. They’re commonly used in hospitals, laboratories, and other settings where clean air is essential; their dense mesh of fibers traps even microscopic particles.

4. Electrostatic Air Filters

Electrostatic air filters use an electric charge to attract and trap airborne particles. These filters consist of multiple layers of electrostatically charged materials that capture particles as they pass through. Electrostatic filters are more efficient than fiberglass filters, though less effective than pleated or HEPA filters.

How Do Air Filters Work?

Air filters work by trapping airborne particles as they pass through a filter media. Its thick substance blocks out dust and other particles from the air while letting clean air flow freely through.

Air filters employ various methods to capture particles. Fiberglass filters use a mechanical method, where particles are trapped within their fibers; pleated filters utilize both mechanical and electrostatic methods, with particles trapped between folds while an electrostatic charge attracts them; HEPA filters combine both mechanical and diffusion techniques so particles collide with fibers and stick to them.

Factors to Consider When Selecting Air Filters

When choosing an air filter, consider:

1. MERV Rating

The MERV rating is a measure of the filter’s efficiency. The higher the MERV rating, the more efficient the filter is at capturing airborne particles. However, a higher MERV rating also means a higher resistance to airflow, which can reduce the efficiency of your HVAC system.

2. Filter Size

Air filters come in various sizes. It’s therefore essential to select one suitable for your HVAC system. A filter that’s too small won’t effectively capture airborne particles while one that is too large may restrict airflow and reduce efficiency of your HVAC unit.

3. Airflow Resistance

As previously discussed, air filters with higher MERV ratings can restrict airflow in your HVAC system. Therefore, it’s essential to select a filter with both high filtration efficiency and minimal resistance for efficient operation of your HVAC system.

4. Types of Air Pollutants

Different air filters are designed to capture different types of pollutants. For instance, if you have pets, one that captures pet dander is ideal. Conversely, those suffering from allergies will benefit from filters which capture pollen and dust mites.

5. Maintenance Requirements

Air filters need regular cleaning or replacement to remain operational. Certain filters, like HEPA filters, require more frequent replacement than others; so it’s essential that you select a filter that meets both your maintenance needs and budget.

Benefits of Air Filters

Air filters provide numerous advantages to your indoor air quality, HVAC system and overall health. Here are some of the most significant advantages associated with using air filters:

1. Improved Indoor Air Quality

Indoor air pollution leads to health issues like respiratory infections and asthma attacks. Air filters remove hazardous particles from the air therefore enhancing the quality of the air you breathe. Filters with higher MERV ratings can capture even smaller particles, such as bacteria and viruses, providing an additional layer of protection against airborne illnesses.

2. Extended HVAC System Life

Air filters protect your HVAC system from particles that could wreak havoc on its components. By preventing accumulation of debris, air filters help extend the life of your HVAC system and minimize repairs or replacement needs.

3. Energy Savings

Maintaining air filters effectively and regularly can improve the efficiency of your HVAC system, cutting energy consumption and saving you money on utility bills. Clogged filters cause the HVAC system to work harder to maintain desired temperatures, increasing energy consumption and raising utility bills. By regularly replacing or cleaning your air filters, you can improve the airflow in your HVAC system, reduce stress on its components and boost its efficiency.

4. Lower Maintenance Costs

Clogged air filters can lead to dust accumulation in your HVAC system, decreasing its efficiency and necessitating maintenance and repairs. By regularly replacing or cleaning air filters, you can prevent debris from building up within the system, thus saving money on expensive fixes and upkeep costs.

5. Protection Against Allergies and Asthma

Air filters can help reduce symptoms of allergies and asthma by trapping airborne particles that trigger these conditions. Filters with higher MERV ratings capture smaller particles such as pollen, dust mites, and pet dander – common allergens – more effectively than others.

6. Reduced Odors

Air filters can help reduce unpleasant odors in your home by trapping particles responsible for them, such as pet dander, cooking odors and smoke. This makes your house more hospitable and pleasant to live in.


Air filters are essential for maintaining indoor air quality. Different types of filters exist, each offering its own features and benefits. When selecting an air filter, consider factors like MERV rating, filter size, and maintenance requirements.




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