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Air Filtration Guide

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Guide on air quality

What does the word MERV mean ? – Minimum Efficiency Reporting Value

ASHRAE and industrial air filters have developed a way to assess the ability of filters to obtain a result of their yields. The test is to test filters to know that she is the particle size that filters can capture. All types of filters are evaluated according to MERV scale. With this comparison system, you can compare the effectiveness of filters that you buy. A high MERV means that it will filter out large particles and very small while a filter with a lower MERV will filter only the larger particles.

Here is a table that summarizes:

# of the groupMERV


Average efficiency
0.3 – 1.0 MicronsE2
Average efficiency
1.0 – 3.0 MicronsE3
Average efficiency
3.0 – 10.0 MicronsFiltration capacity
(ASHRAE 52.1)Contaminants
(per group)



–Less than 20%
Less than 20%
Less than 20%
Less than 20%Less than 65%
65 – 69.9%
70 – 74.9%
75% or morePollen, mites
sanding dust
textile fiber
carpet fiber



–20% – 34.9%
35% – 49.9%
50% – 69.9%
70% – 84.9%–

–Molds, spores
Pet hair
Virus, Formaldehyde
+ Group 1

MERV 12–

–Less than 50%
50% – 64.9%
65% – 79.9%
80% – 89.9%85% or more
85% or more
85% or more
90% or more–

common bacteria
Cigarette smoke
+ Group 2

4MERV 13
MERV 16Less than 75%
75% – 84.9%
85% – 94.9%
95% or more90% or more
90% or more
90% or more
95% or more90% or more
90% or more
90% or more
95% or more–

–paint dust
smoke dust
+ Group 3


What is the life of the furnace filters?

The life of the furnace filter depends on several factors:
The most important factors are: the quality of the filter, the filter thickness and the amount of dust in your home.

Filter thickness of 1″
You have to change your filters every month

Filter thickness of 2″
You have to change your filters every 1 to 2 months

Filter thickness of 4″
You have to change your filters every 3 to 5 months

Filter thickness of 5″
You have to change your filters every 3 to 5 months


How to extend the life of your furnace filter?

Here are 3 techniques to extend the life of your filters:

1- Take a vacuum cleaner (residential) and remove the dust that is stuck to the side of the air inlet filter. Do this every week to extend the life of your filters for about 1 month. It is important not to rub on the filter to leave it in good condition.

2- If you have thicker filters (filter 4 “and 5”) you can use the # 1 technique, however, you’ll quickly notice that the folds of the filter 4 “and 5” are much deeper than small filters. I advise you to use a table spoon or your fingers to clean the inside of the pleated filters. 1 Do this once a week and you will prolong the life of your filters for about 1 month.

3- This technique is necessary if you find that dust is not totally disappeared from the filter. Bring your filter outside and shake it in the direction of the direction of the air (where the dust is stuck). Again, this will greatly help extend the life of your filters. All these techniques work only on quality furnace filters.



What is good air quality ?

Do you remember having been in a place where the air was good? For example in the forest, in a field in the mountains. In fact, all places away from big cities where the majority of outdoor pollution lies with upgraded air. This is what is called a clean air.

Unfortunately, the indoor air of buildings is not as pure as in the places mentioned above for several reasons. In buildings, several contaminant sources are present without you knowing. Building your home is the greatest level of indoor pollutant. The design of your walls, paint, mineral wool present between the walls, carpets, flooring, lumber, kitchen cabinets, sofas and armchairs. All these are a potential danger to deteriorate the quality of the air inside your buildings. In the jargon of the air quality, we call it the Formaldehydes.



What are the health effects?

Everyone reacts differently to poor air quality inside. All problems should be taken with caution as the most sensitive people may develop serious respiratory diseases such as lung cancer, chronic asthma, legionellosis, sarcoidosis and many others.

Maybe in the short term you will not see the effects in the long term, however, a poor quality of indoor air can be devastating to the health of occupants.

Why is it important not to neglect your air filters?
Your air filter is the only filter means for your home (an air exchanger is not a filter, it is used to get fresh air from outside which is partially filtered). The air that is blown by your furnace or HVAC equipment, travel in your home and is mixed with pollutants assets present inside. If your filter is not efficient or simply neglected, the air quality will decline simply because you multiply the carbon monoxide activity when there’s occupant breathing or Formaldehydes.

If you have a furnace oil or natural gas, the use of a filter is even more important to filter the smoke residue that are emitted by combustion. Also, maintain your air conditioning and heating devices is a good way to improve quality have inside.




Filtration goal first remove particles and microorganisms in the air.
As a result, air conditioning and heating devices are used to recirculate and filter the air including several air changes per hour. Various degrees of filtration are possible, depending on the type of filter you use.

Filters with low MERV (4 to 6) are only used to filter large particles while filters with high MERV used to filter out significantly smaller particles.

The risks of poor air quality:

Do you know that the indoor air we breathe can be more polluted than outdoor air?
Risks due to air pollution are now more important than previously thought. Facilities air conditioning and heating greatly influence the air quality especially particulate pollution.



What are fines particles ?

Possières hydrated solid or suspended in the air like dust, soot, smoke, or volatile organic compounds. Their structure allows them to accumulate other toxic substances with extremely negative consequences for health.

In 2012, a death in eight is due to pollution (indoor and outdoor) in the world



Who are the pollutants?

Tobacco smoke:
Residues from secondary and tertiary smoke with long-term consequences.

Radon is an extremely dangerous radioactive gas that is frequently present in our environment. It is the result of the breakdown of uranium in soil, rock and water. It is a colorless, odorless gas.

Gas that is colorless with a typical chemical smell that is emitted from construction products, household products and other non-natural product.

microscopic agents from animals and mites.

Carbon monoxide:
Smoke from burning firewood can be a source of transmission.

Moisture and mold:
Fungi and bacteria suspended in the air when the moisture is sufficient.

Chemical product:
household cleaning products, candles, incense, products for DIY and renovation.


For more information, consult this guide on air quality PDF