Understanding Filter Terminology

The average person doesn't think about their air filters very often.  A lot of people don't think about air filters at all.  That can make that trip to the hardware store, or visit to a website, once or twice a year, when we replace our filters, a bit confusing and challenging.

Don't worry!  We've provided some explanations below that should help to clear things up.

Furnace Filters, Pleated Filters, MERV

The term furnace filter is fairly self-explanatory - it's a filter that goes into your furnace.  The furnace filter goes into your ducting and removes particles like dust, dirt and hair from the air before in enters your furnace.  This is important for two reasons.  The obvious one is that the furnace filter cleans the air you're breathing, inside your home.  The less obvious reason is that your furnace can be damaged and eventually break, if too many particles are allowed through.  That's why a small investment in a furnace filter can save you a lot of money, in the long-term.

Furnace filters generally come in three varieties: pleated filters. throwaway filters and washable filters.

Pleated Filters

One of the most common types of furnace filters you'll see is the pleated furnace filter.  You can tell if a filter is pleated by looking at the front or back of it.  If the filter media inside the frame is fluffy and white, blue and coarse or white and coarse, it's a throwaway filter.  If the filter media is wavy, shaped like the letter "W" over and over across the filter, then it is a pleated filter.  This media is a thermally bonded polypropylene.  Most of the furnace filters on Canada Fine Filters are pleated filters.

Pleated filters have a number of advantages over throwaway and washable filters.  For one thing, they are much more efficient, meaning they allow fewer particles through, into your air and furnace.  For another, pleated filters hold much more dust before needing to be replaced.  The "W" design also has a major advantage; it allows more filter media to be included in the filter, which makes the filter last longer and causes less of a reduction in air pressure.

MERV Rating

Unlike throwaway and washable filters, pleated filters always have a MERV rating.  The MERV rating is a measure of the efficiency of the filter.  A low MERV rating indicates a filter with low efficiency.  A high MERV rating indicates a filter of high efficiency.  Each MERV rating indicates what percentage of all particles it will remove and what percentage of particles of a certain size it will remove.

Canada Fine Filters carries two high MERV ratings of pleated filters:

Merv 11 

Removes a minimum of 95% of all particles and 60-65% of all particles 1-3 microns in size.

Merv 13

Removes a minimum of 98% of all particles and 89-90% of all particles 0.3-1 microns in size.

To have a MERV rating a filter's media must be certified by lab testing.  I general, pleated filters have a MERV rating from 7-13.  Throwaway and washable filters typically perform like a MERV 4 filter, but are rarely actually tested to have a MERV rating.