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MERV Ratings Chart 101

The Minimum Efficiency Reporting Value, or MERV Ratings Chart, rates the effectiveness of air filters according to a measurement scale designed in 1987 by the American Society of Heating, Refrigerating and Air Conditioning Engineers.  This illustrious group of experts created the chart in an effort to improve health, reduce costs and create more energy-efficient HVAC systems.  However, the average homeowner often is unaware that such a chart exists, and if they are aware of it, they haven’t the slightest idea how to read it.  Spencer Air Conditioning & Heating, home of the Comfort Maintenance Plan, offers this basic lesson on the MERV Ratings Chart to help make your home healthier and more energy efficient. 

 Bigger Is Not Always Better

 The MERV Ratings Chart addresses the filter needs of all residential and commercial applications in HVAC.  The chart addresses the fact that various applications have different filtering requirements.  For example, a hospital needs a filter with a higher MERV rating than a residential window air conditioner due to the need for removing bacteria from the air.  However, filters with a high MERV rating are not practical in central HVAC systems due to the large pressure drop caused by dense filters.  Choosing a filter with the proper MERV rating is not only important for protecting the health of those who will inhabit the building, but also to guarantee that your HVAC system runs efficiently.

MERV Ratings Ranges

 The MERV Ratings Chart is designed using the worst-case performance of a filter, and ranges from a low of 1 to a high of 20.  The lowest-rated filters, with a MERV rating between 1 and 4, filter out larger particles such as pollen, dust mites and carpet fibers, while the highest ratings (above 17) filter viruses, carbon dust, sea salt and smoke.  For example, filters ranging from 11 to 13 may be used in an area where tobacco smoke, cooking oil or smog are significant, while filters ranging from 8 to 11 may be used where hair spray or pet dander is significant.

Bacteria vs. Pollen

 Simply explained, the MERV Ratings Chart provides information about which filters provide the best protection against various pollutants.  Pollutants are measured in a range of 0.3 to 10 micrometers.  Dust mites and cockroach debris, which no one really wants to think about as floating around their home, are rated at 10.0 micrometers or higher.  Filters with a less obstructive filter can trap these larger particles, which is fine for many residential and general commercial applications.  However, for those who suffer from asthma or are in areas where the air must be kept cleaner, such as laboratories, tighter filters are necessary to block smaller particle contaminants, such as lead dust, auto emissions and bacteria.  To complicate matters even further, highly-rated filters are necessary in areas where significant contaminants exist, such as sea salt and smoke.  These highly-rated filters are recommended for manufacturing applications.

If you want more information about the exciting world of MERV Ratings Charts or about the filters recommended for your residential or commercial application, visit Spencer AC & Heating online or connect with them on Twitter, YouTubeFacebook or LinkedIn.