MERV Filters — By The Numbers

The filters in your air conditioner are responsible for cleaning the air that flows through your HVAC system, and for trapping and holding contaminants such as dust, pollen, mold and bacteria. When choosing filters for your air conditioning system, pay close attention to their MERV rating. MERV, which stands for minimum efficiency reporting value, is an HVAC industry-standard measurement of filter efficiency. MERV filter numbers tell you how effective the filter is at removing airborne particles from 0.3 to 10 microns in size.

For example, larger particulates such as pollen, dust and mold spores are often between 10 and 30 microns in size. Bacteria are usually two or three microns in size and tobacco smoke about 0.5 micron.

MERV numbers range from one to 16. Higher MERV numbers mean the filter can trap smaller particles.

• MERV 1-4: These low-cost filters are not highly effective. They are most effective at trapping particulates of 10 microns or larger.
• MERV 5-8: These medium-quality filters are usually made of a pleated material that offers more surfaces where particles can collect. Their effectiveness extends to material of three microns or larger.
• MERV 9-12: Filters with these MERV numbers are considered high quality and can remove particulates of one micron and larger.
• MERV 13-16: These are the highest-quality standard filters that will work in most air conditioning systems. They effectively remove the smaller particulates of 0.3 micron.

Even higher quality filters are available, but they usually require specialized mountings and are not commonly found in standard home systems. HEPA (High Efficiency Particulate Air) filters clean the air at a MERV level of 17-20. Care should be taken when using these types of filters, since they can block airflow and possibly cause damage to your HVAC system.

Air-Tro Inc. has been a provider of professional HVAC design, installation, repair and maintenance services to customers in the greater Los Angeles area since 1969. Contact us today for expert information on MERV filter numbers and what they mean in terms of filter efficiency and home comfort.

Our goal is to help educate our customers about energy and home comfort issues (specific to HVAC systems).  For more information about MERV filters and other HVAC topics, visit our website.

Air-Tro Inc. services the greater Los Angeles area as well as the metro areas of Riverside and San Bernardino County.