Air Filtration and M.E.R.V.

In your search for a quality air cleaner to fit your budget, you will encounter enormous amounts of complex information on different testing methods, efficiencies and ratings, most of which is misunderstood. In the following, we hope you find some basic information with which to make an informed decision without being weighed down by pages of seemingly incomprehensible data.


Air filtration is any one of a number of methods to remove particulates (dust, pollen, spores, pet dander, smoke and smudge particles, etc.) from the air within your home. M.E.R.V. is an acronym for Minimum Efficiency Reporting Value, the end result of a test called Standard 52.2-1999 that was developed by A.S.H.R.A.E. (American Society of Heating, Refrigerating and Air Conditioning Engineers) to address an air cleaner’s ability to remove different sized particles from the air. While we would like to give you some basic understanding of this reporting value, please keep in mind that MERV was never intended to be used as a rating system. Unfortunately, many have latched onto it as an “easy” means of choosing one filter over another.

The new ANSI/ASHRAE Standard 52.2-1999 is a test that basically gives information on a filter’s ability to remove particles of different sizes. This test doesn’t completely replace the older ASHRAE Standard 52.1 commonly known as the Dust Spot Test but is to be used together to give as much information as possible about a filter.

Simply put, in the new test, a filter is put at the end of a test duct built to ASHRAE standards. There are 5 main components to the test; the test duct, a blower, a manometer (instrument to measure airflow), a device to feed dust into the duct, and finally the filter being tested which is placed at the end. Different sized particles are fed into the test duct and the filter is analyzed each time to see which particles were missed. This is done 5 times. Initial readings are taken before dust loading and comparative readings are taken after each test. The lowest number in each of the 12 particle sizes is recorded. Initial readings, of course, are the lowest as most filters gain in efficiency as they load. These minimum numbers are the basis for assigning a MERV number.

The problem comes in the numbers used. For example, MERV 1 to 8 filters only use numbers recorded for particle sizes from 3.0 to 10.0 microns compared to MERV 9 to 12 filters which use numbers recorded for particle sizes 1.0 to 10.0 and MERV 13 to 16 take all particle sizes into account. Yet, MERV 1 to 8 filters account for about 75% of the filters used in most homes so the other figures not used should also be considered. So, although the 52.2 test is an improvement over the 52.1 by providing more detailed information on a filter, it only measures 1) what the filter can do in a specific range and 2) how the filter performs at a single point in time.

Therefore, there are still some questions that would determine a filter’s performance:

  • how does filter perform from minimum to maximum dust holding capacity?
  • how does filter perform on the other particle sizes not included in its MERV?
  • how long is the expected life of the filter and realistically, how long in your area?

Note: Please keep in mind that each test is done with a completely clean filter. Some filters’ efficiency go down as they continue to load up or “get dirty” while others actually go up as they load up with dust, etc. In either case, there is a point where the filter is so dirty that it blocks airflow to the furnace motor which then necessitates replacement immediately (hopefully before that). Most manufacturers will give you a guide to go by for time of replacement but an experienced installer will give you the guideline for your area and suggest that you monitor it every few months (or weeks, depending on the air filter) for the first year to determine YOUR replacement timeframe.

Also, not every filter will have a MERV rating. This may not mean the filter is not good, only that is has not been tested using the ASHRAE standard.

Test Comparisons

Test 52.1 (Dust Spot)

  • Resistance to Airflow
  • Dust Spot Efficiency
  • Arrestance Efficiency
  • DHC (dust holding capacity) (VERY IMPORTANT)

Test 52.2 (MERV)

  • Resistance to Airflow
  • MERV


Although each test, 52.1 and 52.2 measures for resistance to airflow, 52.1 (Dust Spot) measures dust spot efficiency (the filter’s ability to remove all particle sizes present in the air being tested) as well as arrestance efficiency (the filter’s ability to remove a synthetic test dust particle from the airstream) and also DHC (dust holding capacity – how much synthetic dust a filter can hold by weight before reaching its highest resistance point.

M.E.R.V. ratings range from 1 to 20 with 20 being the best possible rating. The following gives you a basic idea of what to expect from filters with different ratings:


“1 to 4” (Throw-Away or Electrostatic):

Ability to capture particles 10.0 microns or larger.

Ex. pollen, dust mites, carpet fibers.


“ 5 to 8 ” (Good residential filters/industrial workplaces):

Ability to capture particles from 3.0 to 10.0 microns.

Ex. mold, hair spray, cement dust


“9 – 12” ( Superior residential filter/hospital labs):

Ability to capture particles from 1.0 to 3.0 microns.

Ex. lead dust, milled flour, auto emissions


“9 – 12” ( Superior residential filter/hospital labs):

Ability to capture particles from 1.0 to 3.0 microns.

Ex. lead dust, milled flour, auto emissions


“9 – 12” ( Superior residential filter/hospital labs):

Ability to capture particles from 1.0 to 3.0 microns.

Ex. lead dust, milled flour, auto emissions



  • Viruses
  • Dust
  • Smudging
  • Tobacco Smoke
  • Bacteria
  • Pet Dander
  • Mold
  • Pollen
  • Spores

  • .3 and smaller
  • .01 to 100.0
  • .01 to 5.0
  • .01 to 1.0
  • .3 to 1.0
  • .1 to 10.0
  • 3.0 to 10.0
  • 10 to 100.0
  • 10 to 100.0

Selecting An Air Cleaner

Although MERV is important, make sure you check results from both tests , 52.1 and 52.2 as well as any other detailed data the manufacturer can supply to give you a better idea on how the filter will perform on all particle sizes and in all phases of testing. Look beyond a MERV rating by checking for more detailed specifications. For example, 2 filters can be MERV 6 – one can be an oiled fibreglass filter and another a pleated filter but the pleated filter could offer much higher efficiencies on smaller particle sizes. With a MERV rating as the only source of information, this would tend to be overlooked.

What type of particulates or contaminants are you trying to remove?

What type of maintenance do you wish to do?
Do you have time for semi-monthly or bi-monthly maintenance or do you need something relatively low maintenance like once/year?

How much is upfront cost and maintenance cost?
For example, low capacity pleated filters are low cost and have to be replaced more often but high capacity pleated filters have better DHC (dust holding capacity) and therefore a longer life.

What area do you live in (downtown, industrial, area under construction)?
In these areas, your filter may need to be replaced more often.

Air Cleaners We Carry

Although there are a wide range of air cleaners on the market today, we carry furnace air cleaners only and those we do carry are the ones that have, over and over again, proven their reliability and effectiveness.

The air cleaners below address the most common areas of concern for most homeowners (dust, pollen, spores,etc.). If you have a special concern that might warrant a need for a germicidal air cleaner or a UV air cleaner, please contact us. As a rule, we do not carry these because of cost and some negative aspects of these units. If you would like a quote on custom air filtration, please call us at 403-289-0089.

Lennox Healthy Climate High Efficiency Media Air Cleaner HC10 & HC16
Media Air Cleaner
MERV 11 & MERV 16 – $595.00 installed + gst (Merv11) and $695 installed + gst (Merv16)
.3 and higher. Expandable MERV 16 and MERV 10 high-efficiency filter removes over 95% of indoor allergens, such as dust, pollen, mold spores down to 0.3 microns. Will fit most competitors’ cabinets. Five-year limited warranty on frame and spacers.Filter media must be replaced once per year in Calgary (more often if in downtown or in an area under or near construction). No ozone as no electricity is used.

5-year Limited Warranty; 1-Year Labour Warranty**
**This does not include annual filter media replacement.

Honeywell F300 – *$950 installed & up + gst
Electronic Air Cleaner
Small airborne particles are electrically charged and magnetically attracted to collection plates.
Being electrically charged, the unit does produce ozone which some people may be sensitive to.

*The collection plates (air cells) must be cleaned at least once every 2 months. Recommended process is to wash them with a power wash either at home or at carwash due to the delicate nature of the ionizing wires and plates in the air cells. Although cleaning in a dishwasher is sometimes suggested, some dishwasher manufacturers now advise against this.
We find this is the best one at removing smoke out of the 3 air cleaners listed here.

5-Year Limited Depot PartsWarranty**, 1-Year Labour Warranty
**This does not include prefilters, broken ionizing wires, bent plates or units with water damage.

Our preferred choice of air cleaner is the Lennox Healthy Climate High Efficiency Media Air Cleaner – Merv 11 as it rates above the others in good construction, ease of maintenance and cost of maintenance.

*Prices subject to change without notice.

*This is normal maintenance only. If in the downtown area, or if you are living in an area close to or under construction, you may have to replace the filter or perform maintenance more often.

Custom Design Service

In some instances, such as homes with infloor heating, a typical air cleaner that relies on the movement of forced air cannot be utilized. In these cases, a custom design is needed. Please phone for a free consultation.

Parts Delivery

In Calgary , we offer free delivery of air cleaner filters and parts on orders over $20.00. For smaller orders in Calgary and any orders for areas outside Calgary , we ship by regular mail and add a shipping/handling charge.

Annual Service

As with humidifiers and furnaces, for those of our clients who do not wish to tackle their own mechanical equipment maintenance, we offer an annual reminder & service where the client is phoned at the same time every year to book their once/year service.

Links to Related Websites

All of the following tips apply to the Calgary Area: