The Science Behind Air Filter Longevity: Optimizng Indoor Air Quality

Air filters are an essential component of heating, ventilation, and air conditioning (HVAC) systems. They purify the air by trapping particles, which can include dust, pollen, and other allergens. Many homeowners in Manassas, VA, might be tempted to change their filters frequently with the belief that it ensures better air quality. However, Brooks Heating and Air’s latest study reveals an intriguing reason why changing filters too often may not be the best approach.

Newer filters need time to gather large particles. It's called the caking effect.

Gathering Large Particles

When a new air filter is installed, its pores are relatively large. This means that initially, it primarily captures large particulates from the air. The large particulates accumulate on the filter, causing the pores to become smaller.

As time goes by, the air flow in a filter is tortured by larger particulates, allowing for the capture of smaller particulates

Enhanced Small Particle Capture

As the pores of the filter decrease in size, the filter becomes more efficient in capturing smaller particles. This is because as the larger particles clog the pores, the airflow paths become more tortuous, making it more difficult for smaller particles to pass through. This phenomenon is known as the ‘filter cake’ effect. It means that a slightly dirty filter can actually purify the air more effectively than a brand new one.

Its important to find the right balance of frequency when changing air filters

Balancing Filter Change Frequency

However, there is a balance to be struck. As the filter continues to accumulate particles, it will eventually become too clogged, leading to restricted airflow and potentially causing the HVAC system to work harder. This can result in increased energy consumption and strain on the system. It is essential to find the optimal frequency for changing filters that allows for effective air purification without overburdening the HVAC system.

Brooks Heating and Air Recommends changing filters every 90 days


Experts recommend that standard 1- to 3-inch air filters be replaced every 90 days for an average suburban home. However, if the home has pets or individuals with allergies, it might be beneficial to change the filters more frequently, but not excessively. Brooks Heating and Air recommends that homeowners in Manassas, VA, should closely monitor their filters and consult HVAC professionals for personalized advice. Changing air filters too often can rob them of their increased efficiency in capturing small particles as they age. Striking a balance in filter replacement frequency is key to optimizing indoor air quality while ensuring the longevity and efficiency of your HVAC system. Side note: changing air filters is one of the many benefits our comfort club members receive! We can help take the mystery out of the frequency of changing air filters so you can breathe easier.

For Further Reading

“How Often You Should Change Your Air Filter”, This Old House. Read the article​