All About Air Filters

Arlington, TX – Not all homeowners realize the importance of their air conditioner’s air filter. Using the correct filter is essential for the unit’s performance, air quality, service life, efficiency, and for your comfort. The air filter traps particles that can damage your air conditioner and can potentially help to protect your health. However, air filters were not initially created to provide cleaner air, but to protect the system’s HVAC equipment from harmful particles and debris. The following provides you with information regarding the most common different types of air filters.


Types of Air Filters

types air filtersThere’s a wide variety of AC filters on the market. The most common are fiberglass, pleated, and HEPA filters. Fiberglass filters are a popular choice of homeowners because they are the lowest in cost. They filter out large particles but provide little effectiveness in cleaner air. They do provide minimal protection for your unit. Replace fiberglass filters once per month.

Pleated filters are of higher quality, and will cost you more. They capture finer particles in the air moving through them, than fiberglass filters. The pleats increase the surface area where dust and other contaminants are captured and held. Pleated filters need to be replaced approximately every 3 months. Most HVAC systems can tolerate a pleated filter, but it’s best to check with your air conditioner’s manufacturer or your AC technician before using them. They offer cleaner air than fiberglass filters and middle ground on filter cost.

HEPA filters are the top of the line for cleaner air in your home. They are the ideal choice for family members with allergies, asthma or other respiratory conditions. On average, they capture about 98-99% of airborne particles, including bacteria and viruses. However, only HVAC systems designed specifically for HEPA filters should use them. In systems not designed for a HEPA, the unit will struggle to pull air through them. This can result in rapid wear on the unit, and reduced airflow. If you are not sure about the type of filter you should use, contact the manufacturer or ask your HVAC technician.


MERV Rating

MERV ratings, or the Minimum Efficiency Reporting Value, provides air filters with a scale of 1-20. This number indicates how well the filter is designed to hold contaminants under the least efficient conditions.

merv rating chart


MERV 1-4: Fiberglass, disposable panel, and washable metal/synthetic filters have a MERV rating of 1-4. Filters with this rating are the least effective, but do the job of protecting the AC equipment from harmful particles.


MERV 5-8: Pleated filters are rated between 5-8. This rating is close to the default choice for most systems (6-8). These do a better job of holding smaller particles and allergens for improved air quality.  They are more restrictive than fiberglass filters, but most systems will tolerate them. For those with respiratory issues, a pleated filter may be the solution you need. However, you wouldn’t want to buy an industrial pleated filter for your home unit.

The higher the MERV rating, the denser the filter will be, and the more restricted the air flow will become. This will overload the unit resulting in a breakdown. A pleated filter can be an excellent choice when you want more from filtration. Ensure you choose the right one for your unit to avoid losing efficiency. It’s always best to refer to your units manufacturer or your HVAC technician for questions about the best filter for your HVAC unit.


Higher MERV Ratings

MERV 9-16: Extended pleated and electronic filters are among the more advanced air filters. These are typically ranked between 9-12 and 13-16, respectively. Filters within an 8-13 range will filter out fumes, smoke and smog. MERV 14-20 filters have the capacity to filter out bacteria and viruses. A MERV 20 is typically an industrial unit such as with a hospital.  Hospitals initially used these to reduce the spread of infection. However, as previously stated better isn’t always best for your home’s HVAC system.

It’s critical to avoid selecting an air filter with a MERV rating that is too high for your HVAC system. While you may want a higher MERV rating and improved filtration, it can end up causing damage to your HVAC unit. Again, check with your manufacturer or HVAC technician.


Changing the Air Filter

Generally, when using the inexpensive fiberglass filters, you should change it every 30 days. Pleated air filters typically recommend changing them every three months. Continue to inspect them at least monthly, and change earlier if needed. Remember, excessively dirty filters contaminate the air, your unit, can lead to premature wear on the unit, and reduce energy efficiency. Some air filters are washable. The key things to know regarding washable filters is to properly clean according to the manufacturers instructions. Allow them to completely dry before using. It isn’t a bad idea to have two for this reason.


How to Visually Inspect Your HVAC Air Filters

To inspect the air filter, hold it up to a light source. If the light won’t pass through it, it’s time to change the filter.

Not changing the air filter results in dust and contaminants getting into the system. Air flow becomes restricted, while components of the unit can experience friction and excessive wear and tear due to dust, contaminants, and overwork resulting in increased power bills. This can lead to a breakdown.

Have questions or need AC Service? Call Metro Express Service today. We offer professional services you can count on. We’re available 24/7 for emergency service, and are a member of the BBB.


Randy Murphy

Randy Murphy has been building his knowledge of the air conditioning and heating business for several years now. He first started applying his knowledge while working for his father’s HVAC company. Later, in 1987, Randy started his own business: Metro Express Service. He has been a top 10 Trane & Amana dealer for over eight years. When it comes to heating and cooling, Randy knows the business better than anyone.
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