MERV and Particle Size: Key to Understanding Filter Ratings

MERV and Particle Size: Key to Understanding Filter Ratings

The air in your Pasadena home contains particles such as mold spores, animal dander, bacteria and viruses, all of which can aggravate asthma and allergy symptoms and cause a number of respiratory problems later on. Your first defense against poor indoor air quality indoor air pollutants is your HVAC filter, which you should inspect monthly and replace when dirty. Your filter also ensures optimum air flow and prevents dust from entering and damaging your system.

Choosing the Right Air Filter
The Minimum Efficiency Reporting Value, or MERV, is a standard measure of the ability of an air filter to trap a certain percentage of various sizes of particles. The higher the MERV rating, the better the filter at trapping more, smaller particles.

A rating of 1-4 on the MERV scale indicates a low-quality filter that traps less than 20 percent of particles larger than 10 microns, including dust mites and pollen. These are generally inexpensive, flat filters that do little to improve your air quality.

A rating of 5-8 indicates a medium-quality filter, trapping up to 35 percent of particles as small as 3 microns, including mold spores and hair spray. These filters are pleated to provide more area for trapping particles and are sufficient for most residential needs.

A rating of 9-12 indicates a high-quality filter that can trap up to 95 percent of particles as small as 1 micron, including Legionella and humidifier dust.  Nearly as effective as a true HEPA filter, these higher-quality filters can drastically improve the quality of your air and are particularly helpful for those who suffer from respiratory illnesses such as asthma and COPD, and they considerably reduce allergens that cause allergy symptoms.

Filters rated between 13 and 20 are used only in commercial buildings and manufacturing operations.

It’s essential to check the specs of your system to determine which type of filter it will accommodate. Balancing air cleaning qualities with optimum airflow is important when choosing a filter.

Air-Tro, Inc. has proudly served Pasadena-area residents since 1969. For more expert information on choosing an air filter for your system, please feel free to contact us.