Understanding Air Filter Basics: 5 Terms You Need To Know

The filters you use in your air conditioner or furnace are vital components in HVAC system effectiveness and efficiency. Filters don’t look like much — usually large, rectangular, flattish boxes containing fiberglass or pleated cloth — but they are responsible for keeping your indoor air free from contaminants and helping your heating or cooling system run properly. Here are five characteristics that will help you better understand air filter basics and make a better choice of filters for your home comfort system.Understanding Air Filter Basics: 5 Terms You Need To Know

  1. Initial and sustained efficiency: The initial efficiency is how well the filter works at trapping and holding particulates and contaminants when it’s new. Sustained efficiency is the filter’s effectiveness over time. Efficiency drops as filters get dirty.
  2. Arrestance: Arrestance levels, determined through laboratory testing, indicate how well the filter traps and holds dust particles.
  3. Pressure drop: Sometimes called filter resistance, pressure drop indicates the effect the filter has on airflow within the furnace or air conditioner. Clear and unobstructed airflow is necessary for proper HVAC system operation. If a filter has a high pressure drop rating, it may block that airflow and reduce the unit’s function and efficiency.
  4. Dust holding efficiency: This rating expresses how much dust the filter can hold at a particular pressure drop level. More efficient filters can hold more dust.
  5. MERV rating: Minimum efficiency reporting value, or MERV, ratings are an industry-standard indicator of overall filter efficiency. They describe how well a filter captures and retains particles of 0.3 to 10 microns in size. MERV ratings for residential filters range from 1 to 16; higher numbers mean greater efficiency. HEPA (high-efficiency particulate air) filters, with MERV ratings of 17 to 20, filter out even smaller particles. Use caution with high-MERV filters, however. Some may require special adapters or frames to work properly. They may also be so restrictive to airflow that your HVAC system could be damaged.

Geisel Heating, Air Conditioning & Plumbing serves the greater Cleveland area with home heating, cooling and plumbing services. Contact us today for more information on air filter basics, including performance and efficiency ratings, and for expert help with choosing the right filter for your HVAC system.

Our goal is to help educate our customers in Western Cleveland, Ohio about energy and home comfort issues (specific to HVAC systems).  For more information about air filters and other HVAC topics, download our free Home Comfort Resource guide.

For those Do it Yourselfers who would rather take control of your own indoor comfort, you can shop our online store for replacement parts, products and accessories!   

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