1. Technology of Clean Air
presented by the
National Air Filtration Association
Promoting the Clean Air Industry – Worldwide
Copyright-National Air Filtration Association V8 2015
Thanks for your time and attention.

2. Purpose Understand Air Filtration Principles
Learn About Air Filter Testing Methods
ASHRAE 52.1
ASHRAE 52.2 – MERV
Testing of HEPA Filters
Molecular Phase Contaminant Removal
Adsorption - Activated Carbon
Chemisorption – Potassium Permanganate
Copyright-National Air Filtration Association V8 2015

3. 5 Mechanisms of Particle Filtration
Straining
Impingement
Interception
Diffusion
Electrostatic Attraction
Begin by explaining that most people think of filters as they think of a screen door or colander – particles are removed because they are too large to fit through the openings. Actually, this is the least common mechanism of filtration – then introduce the others.
Copyright-National Air Filtration Association V8 2015 2

4. Straining Very large particles are captured between two fibers. Fiber
Airflow
Particle
Fiber
Airstream
A basic concept is that the functional part of a filter is the media and that media is made up of fibers, be they glass, synthetic, metallic, ceramic, etc. Straining is indeed a mechanism of filtration, but only acts on the largest particles in the air – for instance, leaves, lint, and droplets.
Airflow
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5. Impingement Larger particles do not move around the fiber with the
airstream and are
carried into the
fiber due to their
momentum.
Particle
Airflow
Fiber
Airstream
By a show of hands, how many have an SUV? Let’s put you are in the driver’s seat, the accelerator is strapped at wide open and you are headed toward a forest. You’ll probably miss the first tree, and possibly the second, however the momentum of the car will ultimately hit a tree. Same with big particles traveling at high rates of speed. The airstream will flow around the fiber, but the particle, with more mass, will exit the airstream and impact itself on a fiber.
Airflow
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6. Interception Midsize particles move along with airstream lines
and contact a
Fiber. Fiber and
Particle size
dependent
Airflow
Particle
Fiber
Airstream
Some particles just pass close enough to the fiber that they are attached and held by van der Waal’s forces. These are same charges that allow you to rub a balloon against your hair and stick it to a wall. These are weak electrical charges from the particle and caused by the air moving across the fibers of the filter. Particles cling to the fiber with van der Waal’s forces until another force that is stronger dislodges them. This fact can be proved when you next change your filter. Knock it against the floor and thousands of particles will fall to the floor. The same is true if the particle is overcome by drag forces of the airstream.
Airflow
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7. Diffusion Smaller particles move randomly across airstream
lines and contact
fibers by Brownian
Motion. Optimum
at lower airflows.
Airflow
Fiber
Airstream
Particle
Smaller particles moving at slower speeds are captured because they are literally pushed against the fiber by gas molecules in the air. This mechanism is known as Brownian Movement and you may have seen this as you looked through a microscope in high school biology – the “vibration like” movement of small objects as they are pushed upon by other forces.
Airflow
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8. Electrostatic Attraction
Particles are pulled
to the fiber due to
electrostatic
attraction (charge)
of the fiber, that is
opposite of the
particle charge.
Airflow + -
Particle
Fiber
Airstream
This is similar to Interception – two slides ago with the van der Waal’s forces – however this mechanism is wholly dependant on the particle having a slightly larger concentration of an opposite charge concentrated at one point in the particle that are attracted to the opposite charge of the fiber.
Airflow
Copyright-National Air Filtration Association V8 2015

9. Graph of Principles
Copyright-National Air Filtration Association V6 2010
This graph shows the relationship between Diffusion, Interception and Impingement. Diffusion is higher at lower velocities with smaller particles, impingement is higher at higher velocities with larger particles and Interception is fairly constant with velocities and is particle and fiber size dependant.
Copyright-National Air Filtration Association V8 2015

10. Deposition of Inhaled Particles In Human Respiratory System
Aerodynamic Diameter (micrometer)
Likely Region of Deposit
> 9.0
Filtered by nose
6.0 to 9.0
Pharynx
4.6 to 6.0
Trachea / Primary Bronchi
3.3 to 4.6
Secondary Bronchi
2.15 to 3.3
Terminal Bronchi
0.41 to 2.15
Alveoli
< 0.41
May be exhaled *
Your lungs are the place where the outside comes closest to the inside of your body – about 7 micrometers in diameter. When you don’t use proper filtration in your building, your lungs become a filter. Our nose is a pretty good filter in that it stops the larger particles. All the way down through the airway passage, your bodily forces are working to remove particles of different sizes. Even particles that make it down to the smallest part of your lung – the alveoli (pronounced Al – V – O – li) – are removed by other processes however they can also be lung damaging.
* Ultrafine particles may be removed by diffusion mechanism
Copyright-National Air Filtration Association V8 2015

11. Sizes of Specific Indoor Contaminants
Electron Microscope
Microscope
Naked Eye
0.001 µ
0.01 µ
0.1 µ
0.5 µ
1.0 µ
10 µ µ
Bacteria
Viruses
Tobacco Smoke
Plant Spores
Cooking Smoke / Grease
Dander
Hair
Dust
Fertilizer
Insecticide Dust
Coal Dust
Here is a chart of specific sizes of contaminants. Mold and fungi spores tend to be large and reproduce by spores somewhat like a dandelion, and can be filtered with most MERV 6 air filters.
Bacteria reproduce by cell division and are sized in a broader spectrum and can only be filtered with more efficient filters - MERV 11 and higher.
Viruses reproduce by invading and replicating the DNA of a host organism. Viruses are the smallest of these contaminants and cannot survive for long periods of time outside the host. They normally “ride” on dust or droplet nuclei and can only effectively be removed with HEPA filtration.
Copyright-National Air Filtration Association V8 2015

12. Air Filter Test Methods
ASHRAE 52.1 – (retired)
ANSI/ASHRAE Standard 52.2
HEPA/ULPA
Dioctylphthalate (DOP) MIL STD 282
Poly-alpha olefins (PAO) Institute of Environmental Sciences & Technology
This is why, early on, the air filter industry in conjunction with the American Society of Heating, Refrigerating and Air Conditioning Engineers(ASHRAE) developed test methods to determine the removal efficiency of a filter. These are all industry standard test methods . In the case of HEPA filters, the military utilized specific methods for nuclear particle removal. And UL determined a test for fire rating. The ASHRAE tests are used to compare the performance of one filter to another, not to show real-life performance. The newer ASHRAE test in practice – 52.2 – is now the standard used…ASHRAE Standard 52.1 is being incorporated into 52.2 and will be retired.
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13. ASHRAE 52.1
ASHRAE 52.1 was retired in January of 2009, and is no longer recognized an ASHRAE Test Standard. It joins all other 52 Standards that have been retired including: ASHRAE ASHRAE ASHRAE 52-91
You can help the filter industry by using the correct air filter test standard – this would be ANSI/ASHRAE 52.2 – 2012.
Copyright-National Air Filtration Association V8 2015

14. ANSI/ASHRAE
A destructive test to measure minimum efficiency reporting value (MERV)
Efficiency test aerosol is Potassium Chloride (KCl) particles, 0.3 to 10 micrometers
Dust loading aerosol is ASHRAE Standard Test Dust:
Size classified Arizona Road Dust
Cotton linters
Carbon black
Because the 52.1 test did not measure the size of the particle – just the amount – an ASHRAE Committee was formed and a research project was done to develop a method to show removal by a filter based on particle size. A new challenge aerosol had to be found because outdoor air does not have consistent particle size distribution nor quantity. Potassium chloride was found to be the best and easiest aerosol for this purpose. Also, the Committee wanted to know the minimum efficiency of the filter, rather than average efficiency as reported by ASHRAE The minimum efficiency of the filter is typically in its clean configuration, since it would only become more efficient from this number. And this number, called a Minimum Efficiency Reporting Value (MERV) would be more like the European one-number system.
Copyright-National Air Filtration Association V8 2015

15. ANSI/ASHRAE 52.2 - 2012 Initial Resistance
Pressure required to move air through filter at a certain air flow written in inches water, Pascal or millimeters water
Final Resistance
Pressure at which the filter would be considered fully loaded
Copyright-National Air Filtration Association V8 2015

16. ANSI/ASHRAE 52.2 - 2012 Test Duct Configuration
Outlet
Filters
ASME
Nozzle
Downstream Mixer
Exhaust
HEPA
Room Air
OPC
Inlet
Filters
Aerosol
Generator
Even a new style of test device was developed to help shorten the distance for the particle counter lines. The 52.2 test duct begins by taking laboratory room air that is conditioned to ASHRAE Standard 55 (temp & relative humidity parameters) and using a HEPA filter, removes all particles. Potassium chloride is then injected upstream of the first optical particle counter (OPC) sample point and upstream of the filter under test. The particle counter determines the number and size of particles in the challenge stream. This aerosol then passes through the filter under test and, if not captured, pass around to the second particle counter sample point downstream. The air is then HEPA filtered to remove all remaining particles and recirculated to the laboratory. By this method, we know exactly how many of what size particles are captured by the filter under test. The dust loading is done exactly as in 52.1 and an efficiency test is run between each loading. The final efficiency numbers are used to determine the MERV value.
HEPA
Upstream
Mixer
Device
Section
Blower
Flow
Control
Valve
Backup Filter
Holder (Used
When Dust loading)
Copyright-National Air Filtration Association V8 2015

17. Typical 52.2 Complete Loading Test Data Report
Size Range
(micrometers)
Fractional Efficiency (%) at Resistance (in H20)
Composite
Minimum
Average
0.28
0.32
0.46
0.64
0.82
1.00
0.3 to 0.4
2.7
6.7
17.2
29.4
37.1
37.9
E1 = 9.8
0.4 to 0.55
7.8
15.9
27.7
43.3
53.2
54.6
0.55 to 0.7
11.2
30.2
46.0
60.7
70.5
71.6
0.7 to 1.0
17.6
42.6
59.3
73.7
81.3
81.8
1.0 to 1.3
20.4
51.6
70.3
80.8
83.7
85.2
E2 = 27.2
1.3 to 1.6
23.9
58.2
76.5
84.7
86.1
87.2
1.6 to 2.2
28.3
69.6
84.1
89.1
90.2
91.0
2.2 to 3.0
36.3
83.9
91.9
94.2
94.4
93.2
3.0 to 4.0
39.4
89.4
93.7
95.8
96.4
94.9
E3 = 44.8
4.0 to 5.5
42.8
90.6
95.3
96.5
97.9
95.6
5.5 to 7.0
46.5
92.3
97.1
98.0
98.4
7.0 to 10.0
50.4
94.8
97.5
98.3
100
99.2
After all of the testing and dust loading to final resistance, this is the data produced. Here you see the composite minimum of a MERV 6 filter.
Minimum Efficiency Reporting Value is 6 at 492 fpm
Copyright-National Air Filtration Association V8 2015

18. Composite Minimum Curve
All 52.2 testing comes with a chart showing filter efficiency over the entire test of the filter
Copyright-National Air Filtration Association V8 2015

19. MERV Parameters This is a New Parameter Table as of Sept. 2014
Minimum Efficiency Reporting Value
Composite Average Particle Size Efficiency (%)
Average Arrestance by ASHRAE 52.1
Minimum Final Resistance
0.3 to 1.0 E1
1.0 to 3.0 E2
3.0 to 10 E3 Pa
In Water 1
n/a
E3 < 20
Aavg < 65 75
0.3 2
65 ≤ Aavg < 70 3
70 ≤ Aavg < 75 4
75 ≤ Aavg 5
20 ≤ E3 < 35
150
0.6 6
35 ≤ E3 < 50 7
50 ≤ E3 < 70 8
20<E2
70 ≤ E3 9
35<E2
75 ≥ E3
250
1.0 10
50 ≤ E2 < 65
80 ≥ E3 11
20<E1
65 ≤ E2 < 80
85 ≥ E3 12
35<E1
80 ≥ E2
90 ≥ E3 13
50<E1
90 ≥ E2
350
1.4 14
75 ≤ E1 < 85
95 ≥ E3 15
85 ≤ E1 < 95 16
95<E1
E2 ≥ 90
This chart is used to determine the MERV number. By working backward from the 3.0 to 10 micrometer removal efficiency, one completes the numbers until there is no removal above the stated number in the next column to the left– then across to the MERV number.
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20. MERV Parameters E1 = 9.8% E2 = 27.2% E3 = 44.8% MERV 6
Minimum Efficiency Reporting Value
Composite Average Particle Size Efficiency (%)
Average Arrestance by ASHRAE 52.1
Minimum Final Resistance
0.3 to 1.0 E1
1.0 to 3.0 E2
3.0 to 10 E3 Pa
In Water 1
n/a
E3 < 20
Aavg < 65 75
0.3 2
65 ≤ Aavg < 70 3
70 ≤ Aavg < 75 4
75 ≤ Aavg 5
20 ≤ E3 < 35
150
0.6 6
35 ≤ E3 < 50 7
50 ≤ E3 < 70 8
20<E2
70 ≤ E3 9
35<E2
75 ≥ E3
250
1.0 10
50 ≤ E2 < 65
80 ≥ E3 11
20<E1
65 ≤ E2 < 80
85 ≥ E3 12
35<E1
80 ≥ E2
90 ≥ E3 13
50<E1
90 ≥ E2
350
1.4 14
75 ≤ E1 < 85
95 ≥ E3 15
85 ≤ E1 < 95 16
95<E1
E2 ≥ 90
This chart is used to determine the MERV number. By working backward from the 3.0 to 10 micrometer removal efficiency, one completes the numbers until there is no removal above the stated number in the next column to the left– then across to the MERV number.
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21. How Can Filters Capture Particles Smaller Than 0.3 Micrometers ?
It is crucial to consider the efficiency below 0.3 micrometers
Commonly believed that filters only capture “down to 0.3 micrometers”
Better particle counters show efficiencies below 0.3 micrometers Copyright-National Air Filtration Association V8 2015

22. Addendum B
Added for ability to test lower efficiency filters (MERV 1-4) with an arrestance and dust holding capacity percentage.
Two new items added to 52.2 within the last two meetings of the Standing Standards Project Committee. First, Addendum B was added to bring the testing of lower MERV number filters using the Arrestance test and dust holding capacity from ANSI/ASHRAE 52.1 method of test. This allowed the Committee to retire the 52.1 Standard.
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23. Addendum B
Arrestance – ability of an air cleaning device with efficiencies less than 20% in the size range of 3.0 to 10.0 micrometers to remove loading dust from test air. Average Arrestance - Difference between the weight of the dust fed versus dust passing through the device to final filter calculated as dust captured by test device.
With lower efficiency filters, you will find the arrestance information (explain from slide) and the average arrestance (explain from slide
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24. Addendum B
Dust Holding Capacity – total weight of the synthetic loading dust captured by the air cleaning device over all of the incremental dust loading steps tested to a final resistance of 1.4” wg or specified final resistance.
In addition, total dust in grams captured by the filter under test will be shown. This information can possibly be useful in determining the time in service of a filter.
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25. Informative Appendix J
Optional method of Conditioning a filter using fine KCl particles (0.04 to 0.08 micrometers) on electrically charged (electret) media
Minimum efficiency in some types of may be less than the initial efficiency
The second item added to ANSI/ASHRAE 52.2 is the Informative Appendix J also known as the Conditioning Step. Some electrically enhanced media have the fiber charge blinded by dust then loaded with smaller particles such as those found in the outdoor environment. The conditioning step is designed to provide critical filter applications with a method of determining how much the efficiency will drop in efficiency when loaded with these smaller particles.
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26. Informative Appendix J
This chart shows the initial efficiency using the 52.2 laboratory test and then the tested efficiency of a 2-inch electrostatically charged (electret) media pleated filter after 10 weeks of filtering 100% outdoor air in service. The conditioning step is designed to show how smaller particles captured and bound around the filter fiber blind the charge in some filters and reduce the efficiency from initial. As they continue to load, the mechanical efficiency does occur and increases the filter efficiency.
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27. Informative Appendix J
MERV –A - Added to determine the amount of the efficiency loss a filter may realize in field application
Depending on the critical nature of the application, owner may want to ask for optional Appendix J testing
End users of filters applied in critical applications may want to have their filters tested with the Conditioning Step. When Appendix J testing is done, it is noted by an “A” after the word MERV…for example a MERV 14 filter tested with the conditioning step would have a test report shown MERV A14
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28. HEPA Filter
High Efficiency Particulate Air filter is 99.97% efficient on 0.3 micrometers of a challenge aerosol.
Additionally, HEPA
filters should have
a pressure drop of
not more than 1” w.g.
when tested at
rated flow
HEPA filters also have up to a 1” pressure drop when clean. This specification keeps enough media in the pack to create the efficiency needed for a HEPA.
Copyright-National Air Filtration Association V7 2013

29. HEPA/ULPA Filter Testing
A non-destructive penetration test
Dioctylphthalate (DOP) or poly-alpha olephins (PAO) aerosolized to 0.3 micrometers
Instrument measures overall intensity of light scattered by aerosol both upstream and downstream
Polystyrene latex spheres (PSL) – fractional efficiency measured with particle counter
HEPA filters may be tested to ASHRAE 52.2 Standard (MERV 17-20) however the DOP test has become the standard used for them. This test challenges with DOP or PAO which is aerosolized to a single size 0.3 micrometer particle. Downstream penetration readings determine efficiency of a HEPA. Minimum efficiency of a filter that can be called at HEPA is 99.97% retention of 0.3 micrometer particles. HEPA filters can have efficiencies of % and are called ULPA or % called SULPA – Ultra Low Penetration Air and Super Ultra Low Penetration Air Filters.
Copyright-National Air Filtration Association V8 2015 12

30. HEPA Filter Mechanisms
99.999
0.1
1.0
10.0
0.01
PARTICLE DIAMETER (MICROMETER))
99.99
99.97 99 90 50 10
HEPA FILTER COLLECTION EFFICIENCY
HEPA filters filter higher percentages above and below the 0.3 micrometer size because 0.3 represents the hardest particle to capture as it behaves both like a solid and a gas particle.
COLLECTION EFFICIENCY%)
Copyright-National Air Filtration Association V8 2015

31. UL 900
A destructive design qualification test to measure smoke and flame emitted from a filter when exposed to flame and heated air
Class 1 and Class 2 have been eliminated – now UL Listed
Underwriters’ Labs audit the manufacturer
Only applicable to clean filters
Underwriters Laboratories tests filters for their flammability. Filters should be designed to not support a fire when exposed to flame. One should always look for the UL Listed filters as this means they conform to all insurance company qualifications.
UL used to list filters as Class 1 and Class 2 – now combined to just a UL Listed filter.
Listing only applies to filters in their clean configuration.
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32. Molecular Contaminant Removal Principle Methods
Physical – Adsorption
Activated carbons
Chemical - Chemisorption
Chemically treated activated carbons
Potassium permanganate impregnated media
Because gas molecules are extremely small – much smaller than particles – ranging from 0.01 micrometer and below, they must be captured by a different method than particulate filters. Removal of gas-phase odor molecules is done by the mechanisms of Adsorption and Chemisorption.
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33. Principle Methods
Adsorption - The process by which one substance is attracted and held onto the surface of another.
It is a surface phenomena.
Capacity is independent of particle size
Adsorption rate is inversely proportional to particle size.
The analogy of a sponge soaking up water best describes the process of adsorption (not to be confused with absorption) where the sponge is the same, the water is the same, and the water can be removed from the adsorbent. The activated carbon particle is covered with thousands of holes that are measured in Angstrom Units (10-9). Gas molecules are drawn into these holes and condense and are held until another force acts upon it – usually heat used to liberate the gas and reactivate the carbon.
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34. Molecular Filtration
Now let’s look at chemical and biological odors and other gaseous contaminants and how they can be filtered from the airstream.
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35. Principle Methods
Chemisorption - The result of chemical reactions on and in the surface of the adsorbent.
Fairly specific and depends upon chemical nature of media and the contaminant
Irreversible and essentially instantaneous
Chemisorption is as its name implies, a chemical reaction of a gas molecule with a chemically treated carbon particle or a chemical that has been applied to a substance such as potassium permanganate on activated alumina. The chemisorbent usually converts the gas molecule into carbon dioxide and water vapor. Think of cream added to coffee as once done, it is basically irreversible.
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36. New ASHRAE Standard Standard 145.1
Gaseous contaminant standard developed by ASHRAE
Standard 62 includes recommendations for particle and molecular contaminant removal – especially Ozone O3
There is a new ASHRAE standard under development because ASHRAE Standard 62 includes removal criteria for gaseous contaminants.
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37. Gaseous & Particulate Contaminant Sources
Outdoor Air – too many to list
Ozone, Carbon Monoxide, Nitrogen Dioxide, Sulphur Dioxide
Vehicle Exhaust
Same as above
Office Equipment
VOC’s, Formaldehyde, Carbon Black, Ammonia, Ozone
People
Slide is self explanatory
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38. More Gaseous & Particulate Contaminant Sources
Building Materials and Furnishings
VOC's, Formaldehyde
Cleaning Agents
VOC's,
Environmental Tobacco Smoke
Hundreds
Slide is self explanatory
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39. Summary
Particles captured by Straining, Impingement Interception, Diffusion, and Electrostatic Attraction
ANSI/ASHRAE 52.2 Test Standard is Fractional Efficiency test
MERV and composite curve provides particle size removal efficiencies
Gaseous contaminants removed with Activated Carbon and/or Potassium Permanganate
In summary, particles are captured by several different mechanisms and tested using ASHRAE Standard 52. Gaseous contaminants are much smaller and are captured with activated carbon or chemically treated carbon or potassium permanganate.
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40. The mission of NAFA is to conduct education and certification programs for members and end-user personnel;
To provide forums for the exchange of information about technical standards, government regulations, and product information;
To educate consumers about the importance of air filtration and NAFA's certifications; to certify air filtration products; to set field performance standards for products.
The National Air Filtration Association (NAFA) was formed to provide information and education to its members and the general public. Each year NAFA helps engineers, building owners and facility managers to specify the best filters for their application.
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41. NAFA Programs NAFA Certified Air Filter Specialist - CAFS
NAFA Certified Technician – NCT
NAFA Certified Technician – Level II
NAFA Product Certification
NAFA “Best Practice” Guidelines
And NAFA continues to educate its own member by providing certification programs, technical seminars and national conferences to educate and inform their members. As with any profession, there are many people claiming to understand filtration. Being a NAFA CAFS or NCT assures you the user that this individual has studied and passed a national examination relative to the field of air filtration and knows and understands how to effectively provide your clean air needs.
In addition, NAFA now has a certification program for member products that assures the user that advertised information about product effectiveness and efficiency are backed with scientific testing.
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42. NAFA How we can help you…
Over 230 air filtration manufacturers and distributors
United States and 14 foreign countries
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