Comparing the Effectiveness of Three Types of Furnace Air Filters


The purpose of this experiment was to compare the effectiveness of three different types of air filters used in furnaces. 

I became interested in this idea when I learned that some types of air filters were supposedly better than others. I also have two cousins with asthma. It made me wonder if the more expensive types would filter more pollen and dust to help lessen the chance for them to have an attack. I wanted to see if paying for so-called “better” filters was worth the extra money.

The information gained from this experiment could help people with asthma, or other allergies, and possibly save people money depending on the outcome.


My hypothesis was that the 3-M brand filter would filter more particulate mass from the air.

I based my hypothesis on the “Filtrete’s” packaging graph. The graph shows that the Filtrete micro allergen filter catches the most particulate.


The constants in this study were:

•    The homes used in the study.

•    The time the air filters were left in the house.

•    Method for weighing filters.

•    Use of plastic bags to keep filters uncontaminated during storage.

The manipulated variable was the type of air filter used.

The responding variable was the mass of particles collected in the filter.

To measure the responding variable, I used a triple beam balance to weigh the unused filter before putting it into the home, and again after 3 weeks of use. The difference was the amount of particulate collected.


White garbage bags
Mask (to avoid inhaling any dust)
Triple beam balance
Pair of latex gloves (to keep dust off hands)
Dirt Demon Dust Shield Air Filters
American Air Filters
Filtrate Air Filters


1.    Find 6 home furnaces available for use during testing.

2.    Purchase the same 3 types of filters for each of the 6 furnaces.

3.    Weigh each filter using a triple beam balance.

4.    Write initial mass on each filter using a permanent marker.

5.    Put the filter into a clean plastic bag.

6.    Label bags with permanent marker (name, install date, remove date, size, and return in bag).

7.    Create a rotation schedule to insure that each type of filter gets used for 3 weeks in each furnace on a staggered basis.

8.    Rotation schedule as follows

Houses    Install 11/12 remove 12/3    Install 12/3 remove
12/24    Install 12/24 remove 1/14


9.    Install filters in furnaces (see rotation schedule).

10.    Leave filters in running furnaces for three weeks. 

11.    Collect used filters.

12.    Put filter back in labeled bag.

13.    Install next filter to be used in each of the 6 furnaces (see rotation schedule).

14.    Weigh filters using a triple beam balance.

15.    Calculate difference from initial mass (record).

16.    Repeat steps 10-15 with next filter in schedule for each furnace.

17.    Leave filters in running furnaces for three weeks.

18.    Collect filters.

19.    Put filters in labeled bags.

20.    Weigh filters using a triple beam balance.

21.    Calculate difference from initial mass (record).

22.     Average mass for each type of filter.


The original purpose of this experiment was the purpose of this experiment was to compare the effectiveness of three different types of air filters used in furnaces. 

The results of the experiment were for the American Air Filter average particulate collected was 1.68g, the Dirt Demon Dust Shield’s average was 2.18g, and the Filtrate Air Filter’s average was 3.49g. 


My hypothesis was that the 3-M brand “Filtrete” filter would filter more particulate mass from the air.

The results indicate that this hypothesis should be accepted, because the 3-m brand air filter, overall, collected the most particulate the brands tested.

After thinking about the results of this experiment, I wonder if I were to conduct this experiment in a drier or damper area, would the results be the same?

If I were to conduct this project again I would conduct it in the summer so there would be more dust, pollen, and other particulate to be filtered so a bigger difference in the weight would be present. I would also use more furnaces and do more tests. I’d leave the filters in longer, at least a month, maybe five weeks. My results showed some strange and inconsistent values. I would redo my experiment with much greater care taken when weighing the filters and recording scores.

Researched by ----- Cassidy B


Furnace Filters Canada said...

Furnace air filters are removable elements that fit into the furnace, generally close to the air intake. The idea of a furnace air filter is to guard the motor in the furnace unit from small particles of airborne dust that may cause damage to the motor.

Furnace Air Filters

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