How Often Should You Check Your Air Filter MERV Rating for Clogging?

When was the last time you checked your air filter MERV rating for clogging? If it's been awhile, it might be time to take a look. This small task can make a big difference in the air quality of your home or business.

Air filters are an important line of defense against indoor air pollution. As air passes through the filter, particles and contaminants are trapped, preventing them from circulating through the air. But if the filter becomes clogged, it can't do its job effectively.

So, how often should you be checking your air filter MERV rating for clogging? The answer depends on a few factors, but generally speaking, it's a good idea to check it every 30 days or so. This way, you can ensure that your air filter is working efficiently and keeping your indoor air as clean and healthy as possible.

What is MERV Rating?

When looking to purchase an air filter, you might have come across the term “MERV rating.” This rating is essential in understanding the filter's efficiency in removing particles from the air.

MERV stands for Minimum Efficiency Reporting Value, and it is a measurement scale that ranges from 1-20. The higher the MERV rating, the more efficient the filter is at capturing smaller-sized particles like pollen, pet dander, and dust.

The MERV rating system was developed by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). The scale measures the filter's ability to capture particles between 0.3 and 10 microns in size.

Filtration efficiency is an essential factor to consider when deciding on an air filter. A higher MERV rating means that the air filter will capture more particles, but it also means that it can restrict airflow. So, choosing the right MERV rating for your home or office will depend on various factors like the size of your HVAC system, the number of people present, and the presence of pets or allergies.

In conclusion, understanding the MERV rating system is crucial in selecting an air filter that can efficiently remove airborne particles from your home or office. Make sure to choose the right MERV rating that balances filtration efficiency and airflow restriction.

Effects of a Clogged Air Filter

A clogged air filter can have several negative effects on your HVAC system and indoor air quality. Here are two of the most significant effects:

1. Reduced Airflow: As your air filter becomes clogged with debris, the airflow in your HVAC system is progressively restricted. This restricted airflow causes the system to work harder to pull air into the unit, resulting in extra strain on the system's motor. As a result, you may notice that it takes longer to cool or heat your home, and you may also experience uneven temperature distribution in different parts of your home.

2. Poor Indoor Air Quality: If your air filter is clogged, it won't be able to filter out airborne particles effectively. These particles can include dust, pollen, and mold spores, which can aggravate allergies and respiratory problems. Additionally, clogged air filters create a breeding ground for mold and bacteria to grow, worsening the quality of the air you breathe.

In conclusion, it's essential to check your air filter's MERV rating regularly and replace it when necessary to avoid the negative effects of a clogged air filter. Doing so will help ensure the efficient and consistent operation of your HVAC system and contribute to excellent indoor air quality for you and your family.

Factors that Affect Air Filter MERV Rating Clogging

Air filters play an important role in keeping our indoor air clean and healthy. However, they can become clogged over time, which reduces their efficiency and effectiveness. Several factors can contribute to air filter MERV rating clogging:

1. Frequency of use: The more you use your HVAC system, the more quickly your air filter will become clogged. If you use your system frequently, it's important to check your filter regularly and replace it as needed.

2. Air quality: The air quality in your home can also affect how quickly your air filter becomes clogged. If you live in an area with high levels of pollution, allergens, or dust, your filter may become clogged more quickly than if you live in an area with cleaner air.

3. Presence of pets: Pets can also contribute to air filter MERV rating clogging. Pet hair, dander, and dirt can accumulate in your air filter, leading to reduced efficiency over time. If you have pets, it's important to check your air filter regularly and replace it as needed.

4. Type and quality of the air filter: Not all air filters are created equal. Some filters are designed to be more efficient than others, while some are made with lower-quality materials that may clog more quickly. Choosing a high-quality air filter with a high MERV rating can help you avoid this problem.

By paying attention to these factors and taking steps to address them, you can help ensure that your air filter remains clean and efficient, providing you with healthy, clean indoor air for years to come.

How to check your air filter MERV rating for clogging

The first step to checking your air filter MERV rating for clogging is to locate your air filter. The location of your air filter can vary depending on your HVAC system's make and model. Common locations include the air return grille, furnace or air handler cabinet, or ductwork near the indoor unit.

Once you have located your air filter, remove it from its housing. Take a close look at the filter for signs of debris, dust, and dirt buildup. If the filter appears gray or dark, it may be time to replace it, regardless of its MERV rating.

If there is no visible buildup, check the filter's MERV rating. The filter's MERV rating is usually printed on the filter or its packaging. If you cannot locate this information, refer to the manufacturer's instructions or contact them for assistance. Once you know the MERV rating, compare it to the guidelines provided by the manufacturer.

If the filter is starting to get clogged, but its lifespan has not been met, it may be possible to clean it. Depending on the type of filter and manufacturer's instructions, you may be able to use a vacuum cleaner to remove excess debris or rinse it with water. However, be careful not to damage the filter during cleaning, as this can lower its MERV rating.

It is essential to check your air filter regularly, especially during times of high usage or if you have pets or allergies. By keeping your air filter clean and unclogged, you can improve your indoor air quality, save money on energy bills, and prolong the lifespan of your HVAC system.

5 Tips to Maintain Air Filter MERV Rating Efficiency and Longevity

1. Follow the Recommended Replacement Schedule

Filters that are not replaced regularly can become clogged, leading to reduced airflow and decreased efficiency. Be sure to check the manufacturer's recommendation for how frequently your particular air filter should be replaced, and stick to that schedule.

2. Clean or Replace the Filter When Necessary

If you notice that your filter is becoming dirty or clogged before the recommended replacement date, it's important to take action. Depending on the type of filter, you may be able to clean it yourself, or you may need to replace it entirely. Always consult with the manufacturer's recommendations or a professional if you're unsure.

3. Choose a Filter with a High MERV Rating that is Appropriate for your HVAC System and Indoor Air Quality Needs

When shopping for a new air filter, it's important to choose one with a MERV rating that matches your needs. A higher MERV rating means a filter can capture smaller particles, but it can also restrict airflow, leading to reduced efficiency. Be sure to choose a filter that is appropriate for your HVAC system and indoor air quality needs.

4. Regular HVAC Maintenance

In addition to regularly replacing your air filter, it's important to schedule routine HVAC maintenance. This can help identify and address any issues before they become larger problems, and can also improve the overall efficiency of your system. Be sure to consult a professional for any maintenance or repair needs.

5. Duct Cleaning

Over time, your HVAC system's ductwork can become clogged with dirt, dust, and other debris. This can restrict airflow and reduce the efficiency of your system. Having your ductwork cleaned regularly can help keep your system running smoothly, and can also improve indoor air quality.

By following these tips, you can help maintain the efficiency and longevity of your air filter and HVAC system, ensuring clean and healthy air in your home or workplace.


Checking your air filter MERV rating for clogging is crucial for maintaining good indoor air quality and preventing long-term damage to your HVAC system. The frequency at which you should check your air filter depends on various factors, such as the type of filter, the level of air pollution in your area, and your usage pattern. However, as a general rule, you should check your filter every 1-3 months and replace it when it's dirty or clogged. Remember, a clean and efficient filter not only keeps your indoor air fresh and healthy but also helps you save money on energy bills and expensive repairs in the long run. So, make sure to stay proactive and take care of your air filter regularly!

Frequently Asked Question

MERV stands for Minimum Efficiency Reporting Value - a scale created by ASHRAE to measure the effectiveness of filters in removing different sized particles. For example, a MERV-13 filter is designed to catch 90% of particles 3-10 µm in size, 85% of particles 1-3 µm in size (PM2.5), and 50% of particles 0.3-1 µm in size. Generally, filters with higher MERV ratings are better at catching higher percentages of particles, including the smaller ones.

When you install a filter in the airstream, it will create resistance. The amount of resistance depends on the type of filter material and the amount of area it covers. Standard fiberglass filters don’t generate much resistance, though it increases as the filter gets dirtier. To remove more pollutants from the air, you can use a filter with a different material such as a high MERV filter. These filters have smaller pores, which allow them to catch more pollutants, but also create higher resistance.

The problem with this is that the blower and furnace are only designed to handle a certain amount of pressure drop. Too much resistance means the air flow is low, making the heat exchanger get hotter and potentially crack. On the plus side, low air flow can result in better dehumidification in humid climates, as long as the air flow isn’t so low that it turns the condensate to ice.

So, the answer to the question is: yes, higher MERV filters are better, but you need to find the right balance between air flow, resistance, and effectiveness.

Air filters are designed to capture airborne particles, which can be anything from dust and pollen to mold spores and bacteria. The filter works by drawing air through itself and trapping the particles in the web of fibers that make up the filter.

What are the types of air filters

There are many different types of air filters available on the market. The type of filter you need will depend on the specific needs of your facility. Some common types of air filters include MERV, HEPA, activated carbon, and ultraviolet (UV) germicidal irradiation.

MERV: MERV stands for Minimum Efficiency Reporting Value. MERV ratings range from MERV-0 to MERV-16. The higher the MERV rating, the more efficient the filter is at capturing particles.

HEPA: HEPA filters are a type of air filter that is designed to capture very small particles. A true HEPA filter has a MERV rating of 17-20.

Activated carbon: Activated carbon filters are designed to remove gases and odors from the air.

UV germicidal irradiation: UV germicidal irradiation is a type of light that is used to kill bacteria and viruses.

There are pleated filters and panel filters. MERV 13 filters are pleated, while MERV 16 filters can be either pleated or panel. Pleated filters have more surface area because they are made up of multiple layers of filter media. The pleats create more space for the air to flow through, and the more layers of filter media there are, the more particles can be captured.

HEPA filters are usually pleated, but they can also be panel.

What are the differences between MERV 13 vs HEPA filters

While MERV 13 and HEPA filters both remove particles from the air, they work in different ways.

MERV 13 filters are designed to remove particles that are larger than 0.30 microns, while HEPA filters are designed to remove particles that are smaller than 0.30 microns. MERV 13 filters are often used in commercial and industrial settings, while HEPA filters are often used in hospitals and other medical settings.

MERV 13 filters are more efficient at removing large particles from the air, while HEPA filters are more efficient at removing small particles from the air. MERV 13 filters can remove up to 99.97% of particles from the air, while HEPA filters can remove up to 99.99% of particles from the air.

MERV 13 filters are less expensive than HEPA filters, and they can be used in a wider variety of settings. However, HEPA filters are more effective at removing small particles from the air, and they can be used in settings where MERV 13 filters cannot.

MERV and HEPA filters both work to capture airborne particles, but they do so in different ways. MERV 13 filters are designed to capture particles larger than 0.30 microns, while HEPA filters are designed to capture particles smaller than 0.30 microns. MERV 13 filters are more efficient at removing large particles from the air, while HEPA filters are better at capturing small particles. 

MERV 13 filters are less expensive and can be used in a wider variety of settings, but they can only remove up to 99.97% of particles from the air. On the other hand, HEPA filters are more expensive but can remove up to 99.99% of particles, making them ideal for medical settings. In short, MERV 13 filters are great for everyday use, while HEPA filters are better for specialized environments.

Your HVAC system includes a furnace, air conditioner, or heat pump. It's essential to keep these systems clean and efficient by regularly replacing the air filters. To do this, you'll need to know about MERV ratings.

The air filter in your HVAC system serves two key functions: it protects your system from dust, and it helps clean the air in your home. When the filter is clogged, dust can build up in the system, and the equipment may overheat and fail.

How often the air filter needs to be changed depends on your home's size, where you live, and if you have pets. Inspect it every month, and replace it when you can't see the filter material through the dust.

When choosing an air filter, refer to the specifications of your HVAC system to determine the size. The MERV scale is used to measure the filter's ability to remove particles from the air, and ratings range from 1 to 20, with lower ratings meaning lower-quality filters.

Remember to balance air cleaning with air flow when upgrading your filter to a higher MERV rating. Too dense of a filter can cause air flow restriction and harm your system. Ask your HVAC technician for advice when in doubt.

Replacing the air filter is easy. Open the blower compartment located between the air return and the furnace or air handler. Put the used filter in a plastic bag, then insert the new filter with the arrows pointing in the direction of the airflow.

MERV 11 filters used to be thought of as air flow restrictors, but this is no longer necessarily the case. Home Energy's 2009 experimental test concluded that the pressure drop of high-MERV filters isn't as severe as it used to be. If you're renting and don't have any special needs, then a standard, cheap fiberglass filter with a cardboard frame is fine to use every three months. But if you own your home, then it's worth investing in a more durable filter.

Pleated filters with more pleats per foot are the better option and should be more effective at improving indoor air quality. However, the price can be an issue. A standard 16x25x1 11 MERV filter will cost around $5, but you can save a bit if you buy them in packs of 12. Filtrete, Purolator, and Nordic Pure are all trusted brands.

If you plan to buy washable filters, be aware that cheaper models may have loose filter media after washing and won't perform as well. Disposable filters are also more hygienic since they remove all the dirt from the air. Keep in mind that the more pleats per foot, the better the filter will be.

So, when it comes to MERV 11, the issue of air flow restriction isn't as big as it used to be. With the right filter, you can improve your indoor air quality without having to worry about a pressure drop. Make sure to replace your filter every three months for the best performance.

MERV ratings are used to compare filters to determine which is most effective for eliminating pollutants in a home or office. The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) developed the Minimum Efficiency Reporting Value (MERV) system to measure how well an air filter captures common airborne particles. There are 16 MERV values, ranging from 1 to 16, and the efficiency increases with the MERV number.

Filters are tested against 12 size ranges of particles, with the smallest being around 0.3 microns and the largest around 10 microns. To give a sense of the size, a micron is one millionth of a meter and a strand of human hair is approximately 75 to 100 microns.

The MERV rating is determined by measuring the particle count upstream and downstream of the filter being tested over six intervals, beginning with a clean filter. Afterward, a special ASHRAE test dust is added for five additional measurement cycles. The filter’s performance is determined by calculating the particle density before and after passing through the filter, and then assigning a MERV rating.

The MERV 8 filter is the most common filter in the U.S. Understanding how MERV ratings work can help you understand why it's so popular and how to choose the most beneficial filter for your needs.