Air Filters, They are More Complex Than You Knew w/ Lee Andrews (Podcast)

In today's podcast episode, Lee Andrews with Andrews Filters talks about the complicated and important topic of air filters and filtration. He also explains why they should matter to you and your customers. As indoor air quality (IAQ) becomes more important in HVAC work, air filters will become even more important than they already are.

We classify air filters by MERV ratings. MERV ratings describe the ability of filters to capture finer particles; a MERV 11 filter will catch a lot more particles than a MERV 6 filter. Most air particulates are an average of 0.4 microns large, but most air filters only catch 5-15% of those particulates. The filter industry aims to catch smaller and smaller particulates to improve indoor air quality, protect equipment, and keep consumers healthier.

However, MERV is not a comprehensive value for efficiency. The actual filter media is also important for a filter's efficiency. Higher-quality, finer fibers will have a higher probability of catching smaller particulates. Having a greater surface area (more pleats) also increases performance. The media has a small charge, which helps a filter collect particles. Humidity, particulate insulation (dirtiness), and alcoholic pollutants (such as diesel) can discharge a filter and reduce efficiency.

Many people use MERV 8 filters, but very few understand the difference between MERV 8 and MERV 8A filters. The addendum of the MERV test (A) uses an alcohol-type product to remove the charge. So, MERV-tested filters without the addendum test can actually perform at a lower-rated level. For example, a MERV 8 filter could perform more like a MERV 5-6 filter.

Bryan and Lee also discuss:

  • Electrostatic charge and airflow
  • MERV 8 vs. MERV 8A
  • Loading and unloading
  • Board materials
  • Filter design and sizing
  • Talking to customers about filters
  • Energy savings

Check out Andrews Filter's website at

Check out Refrigeration Technologies' chemical products HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.




To continue you need to agree to our terms.

The HVAC School site, podcast and tech tips
made possible by generous support from