1. ANSI/ASHRAE Standard 145.2: Interpreting Results
Brad Stanley
AAF International
Global Technical Support Leader
Have you ever received a test report and asked the question “What does this mean?”.
This happens to us many times when we receive test reports full of data.
The goal of this presentation is to help you understand what takes place in the ASHRAE test and how to interpret the data. The final result will be to compare filters and know how to decide which is best. I can’t say this is “dummy-proof”, but I will lay out a method to do that here.

2. NAFA 2015 Technical Seminar
Agenda
Introduction
Defining Gas-Phase Filters
Examples
ASHRAE 145.2
Test Apparatus, Method, & Procedure
Test Report Contents
Example of Data Comparison
Now lets get on with our presentation and see what will be covered over the next hour.
First, I will provide an introduction for gas-phase filters. This will lay the foundation for how such filters are tested.
Next is a summary of the ASHRAE test method and test report contents (or data).
Finally, I will give an example of comparing data from several filter test reports.
NAFA 2015 Technical Seminar

3. Defining Gas-Phase Filters (1)
Which is the gas-phase filter?
Hard
Easy
NAFA 2015 Technical Seminar

4. Defining Gas-Phase Filters (2)
Particulate Filters
First, lets do a quick comparison of Gas-Phase Filters and Particulate filters. One main difference is the contaminants they remove.
This is a chart showing the general diameter ranges of various contaminants. Its not meant to be exact, but to provide the general ranges. Many of these are probably familiar to you. Lint, we all know lint, right? Lint is in the range of microns. You are familiar with Lint and have probably seen it with your eyes. If we move toward the left, we encounter contaminants that are sometimes seen and sometimes not seen.
An example is tobacco smoke. Everyone has probably seen tobacco smoke, but as it disperses it becomes more transparent. It is in the range of 1/100 (0.01) -1 micron. You can see this on the chart.
Now let’s think about Gas Molecules. Gas Molecules are less familiar. Do you know what a gas molecule of sulfur dioxide looks like? Most of us would probably say no, because we have not seen sulfur dioxide molecule with our eyes. Gas molecules are in the range of 1/10,000 – 1/1,000 of a micron in diameter.
These differences in size point toward a difference in how the contaminants are removed. Gas-phase filters use different mechanisms than particulate filters and thus require a different test method – ASHRAE
 Different Test Methods Required
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5. Gas-Phase Filter Examples (1)
Pleated Gas-Phase Filter
(Example Properties, 2” Filter)
Function
Gas-Phase & Particulate or Gas-Phase Only
Sheet Thickness
2-5 mm
Media Particle Size
20x50 mesh
(0.85 x 0.3 mm)
Velocity – Filter
500 ft/min
Velocity – Media
217 ft/min
Residence Time
0.005 sec
Mass Carbon / Airflow (CFM)
lb/cfm
Pleated Gas-Phase Filter
Let’s look at a couple configurations of gas-phase filters.
Configuration 1 shown here looks very similar to a particulate filter. However, you can see in the media close-ups, that the media encapsulates or contains carbon particles of small mesh size.
In the gas-phase industry, we would typically call this a pleated gas-phase filter. It can function as a combination filter, which means it removes both gases and particulates OR it can function as a gas-phase only filter, which means it is only intended to remove gases. I am going to quickly go through example properties of a filter so you can see how different gas-phase filters can differ.
The bed thickness or media thickness in a pleated filter refers to the thickness of the material that is pleated, as opposed to the depth of the pleat. It is approximately 2-5 mm thick.
The particle size of the carbon contained in the filter is in the range of 20x50 mesh or 0.85 – 0.3 mm.
The typical Filter face velocity is 500 fpm.
The example the face velocity across the media that is pleated inside the filter is how quickly the air would pass through this media if we stretched it out, flattened out all the pleats inside the filter. The example velocity would be 32 fpm.
The residence time how long the air stays in contact with the media. The example here is 0.01 seconds.
The example amount of carbon per unit of airflow or lb/cfm is lb/cfm
Let’s compare this to Configuration 2.
Media Close-up
Type A
Media Close-up
Type B
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6. Gas-Phase Filter Examples (2)
Granular or Pelletized Media Holding Device (Example Properties)
Function
Gas-Phase Only
Bed Thickness
1-3 in
(25-75 mm)
Media Particle Size
4x6 mesh
(4.75 x 3.35 mm)
Velocity – Filter
ft/min
Velocity – Media
83 – 125 ft/min
Residence Time
0.06 – 0.12 sec
Mass Carbon / Airflow (CFM)
0.03 – 0.06 lb/cfm
Media Holding Device
Configuration 2, looks very different from a particulate filter. This is typically called a gas-phase media holding device or Gas-Phase Cassette or Gas-Phase Module. It is a device intended to hold granular or pelletized carbon (carbon of much larger size than the pleated gas-phase filters).
You can see an ISO view of the cassette and a side view in the top left corner of the slide. The side view shows a “V-bank” inside the cassette, which is where the gas-phase media is held (an example of gas-phase media is carbon) . Media Close-Ups are shown in the bottom left hand corner. Type A is carbon. Type B is potassium permanganate impregnated media. Both of these are in the range of 4x6 mesh or approximately 4 mm in diameter.
Lets go through the properties of this filter and compare to the gas-phase pleated filter.
The function of this “filter” is only to remove gas-phase contaminants.
The bed thickness is 1-3 inches.
The media particle size is 4x6 mesh (~ 4 mm)
The face velocity across the filter or cassette is fpm.
The velocity through the media is fpm
The residence time is 0.06 – 0.12 seconds
The media mass per unit airflow is lb/cfm.
You can see that the Bed Thickness, Media Particle Size, Residence Time, and Mass of Carbon per Unit of Airflow are approximately 10 times greater than the pleated gas-phase filter.
This points to the fact that we need to have knowledge of what filter was tested when comparing test results. This will come up again later in the presentation.
Media Close-up
Type A
Media Close-up
Type B
~10 Times Greater Than Pleated
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7. NAFA 2015 Technical Seminar
ASHRAE Test Apparatus
The test apparatus or test duct is shown in this diagram.
You can see the fan in the lower right hand corner. The airflow comes into the fan from the top then proceeds through the duct from the bottom right hand side toward the left and then up and around.
If I proceed in the direction of airflow, the components you see on the diagram are as follows. First are the Gas Injection points to inject the challenge gas. Next are the Upstream Gas Sampling ports to measure the gas concentration upstream of the test filter. Next is the Test Filter location. This is where the filter being tested is inserted into the duct. After the turn comes the Downstream Gas Sampling ports to measure the concentration of gas downstream of the filter. After these is the Downstream Scrubbing Beds used to clean up any remaining concentration gas. The next section is the Exhaust to the Roof and Inlet from the Room. These allow the duct to bring in conditioned air from the room and exhaust the air out above the roof. The final section is the Temp and RH Control section, which is self explanatory.
Essentially a Modified ASHRAE 52.2 Rig
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8. NAFA 2015 Technical Seminar
ASHRAE Test Method
ASHRAE Laboratory Test Method for Assessing the Performance of Gas-Phase Air-Cleaning Systems: Air-Cleaning Devices.
Controlled Parameters
airflow, contaminant concentration, relative humidity, temperature
Measured Parameters
concentration (upstream and downstream), pressure drop (resistance), time
Two Components of the Test
Component 1 – Initial Efficiency Test (low ~realistic concentration, 1 hr)
Component 2 - Capacity Test (high concentration, 4 hr or 95% breakthrough)
Now lets get into the specifics of the Test Method
The standard name is ASHRAE – Laboratory Test Method for Assessing the Performance of Gas-Phase Air-Cleaning Systems: Air Cleaning Devices.
Parameters that are controlled during the test are: airflow, contaminant concentration, relative humidity, and temperature.
Parameters that are measured during the tests are: upstream and downstream concentration, pressure drop or resistance, and time.
There are two components to the test:
Component 1 is the Initial Efficiency test which is meant to be at a concentration which is low and more realistic. It lasts for 1 hour.
Component 2 is the Capacity Test. It is performed at a high concentration and lasts 4 hours.
Both tests are meant to allow comparison between filters and may not be necessarily representative of what will happen in the field.
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9. ASHRAE 145.2 Procedure Initial Efficiency Capacity
This chart is a graphical representation of the test procedure using Toluene as an example. The Initial Efficiency test is carried out for one hour at a concentration of 400 ppb. The Capacity Test follows for a period of 4 hrs at a concentration of 50 ppm or 95% breakthrough whichever is first. Therefore, the total test time is approximately 5 hours.
Initial Efficiency
(1 hr, 400 ppb)
Capacity
(4 hr or 95% Breakthrough, 50 ppm)
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10. NAFA 2015 Technical Seminar
Test Report Contents
Standard information
Test lab identification
Test lab equipment description
Description of tested filter
Test Conditions
Airflow, challenge gas, relative humidity, temperature
Test Results
Challenge gas concentration
Pressure drop at airflow rate
Respective result (initial efficiency or capacity)
Tabulated Data of pressure drop versus airflow rate
Tabulated Data of upstream and downstream concentration
Here you can see the items required to be on the test report.
Frist is Standard Information related to the laboratory, laboratory equipment, and the tested filter.
Second is the Test Conditions. These would be the airflow, challenge gas, relative humidity, and. Temperature.
The Final section is the Test Results. This consists of the actually achieved Challenge Gas Concentration. The pressure drop measured at the airflow rate. The Initial Efficiency and Capacity at 4 hours or at 95% breakthrough. Then there is tabulated data of the pressure drop versus airflow rate and Tabulated Data of upstream and downstream concentration versus time.
NAFA 2015 Technical Seminar

11. NAFA 2015 Technical Seminar
Report Example (1)
Here you can see the items required to be on the test report.
Frist is Standard Information related to the laboratory, laboratory equipment, and the tested filter.
Second is the Test Conditions. These would be the airflow, challenge gas, relative humidity, and. Temperature.
The Final section is the Test Results. This consists of the actually achieved Challenge Gas Concentration. The pressure drop measured at the airflow rate. The Initial Efficiency and Capacity at 4 hours or at 95% breakthrough. Then there is tabulated data of the pressure drop versus airflow rate and Tabulated Data of upstream and downstream concentration versus time.
NAFA 2015 Technical Seminar

12. NAFA 2015 Technical Seminar
Report Example (2)
Here you can see the items required to be on the test report.
Frist is Standard Information related to the laboratory, laboratory equipment, and the tested filter.
Second is the Test Conditions. These would be the airflow, challenge gas, relative humidity, and. Temperature.
The Final section is the Test Results. This consists of the actually achieved Challenge Gas Concentration. The pressure drop measured at the airflow rate. The Initial Efficiency and Capacity at 4 hours or at 95% breakthrough. Then there is tabulated data of the pressure drop versus airflow rate and Tabulated Data of upstream and downstream concentration versus time.
NAFA 2015 Technical Seminar

13. NAFA 2015 Technical Seminar
Report Example (3)
Here you can see the items required to be on the test report.
Frist is Standard Information related to the laboratory, laboratory equipment, and the tested filter.
Second is the Test Conditions. These would be the airflow, challenge gas, relative humidity, and. Temperature.
The Final section is the Test Results. This consists of the actually achieved Challenge Gas Concentration. The pressure drop measured at the airflow rate. The Initial Efficiency and Capacity at 4 hours or at 95% breakthrough. Then there is tabulated data of the pressure drop versus airflow rate and Tabulated Data of upstream and downstream concentration versus time.
NAFA 2015 Technical Seminar

14. NAFA 2015 Technical Seminar
Report Example (4)
Here you can see the items required to be on the test report.
Frist is Standard Information related to the laboratory, laboratory equipment, and the tested filter.
Second is the Test Conditions. These would be the airflow, challenge gas, relative humidity, and. Temperature.
The Final section is the Test Results. This consists of the actually achieved Challenge Gas Concentration. The pressure drop measured at the airflow rate. The Initial Efficiency and Capacity at 4 hours or at 95% breakthrough. Then there is tabulated data of the pressure drop versus airflow rate and Tabulated Data of upstream and downstream concentration versus time.
NAFA 2015 Technical Seminar

15. Example Data Comparison (1)
In an ideal world, the best filter would have the following:
Pressure Drop (DP) = lowest
Efficiency (Average Initial) = highest
Capacity all points) = highest
Typical filter comparisons are more complex
Final filter selection
First step, obtain an informed man. recommendation
Second step, compare test data
Now that we have a good basis for understanding the ASHRAE test, lets look at comparing filter test data.
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16. Example Data Comparison (2)
Property
Filter X
Filter Y
Filter Z
Test Conditions
Airflow (cfm)
2000
Temp (ºF) 75 77 76
RH (%) 53 46
Challenge Gas
Toluene
Test Results
DP (iwg)
0.64
0.30
0.49
Eff. Challenge (ppb)
368
383
380
Eff. (avg. init.)
62%
12%
64%
Capacity Challenge (ppm)
51.1
49.9
50.0
Capacity (test end, g)
149.9
63.8
173.4
Capacity Test End 4% 6% 5%
Test Time (min) 87 21 92 
0.3 iwg is lowest and the difference from the others is more than the typical accuracy of pressure gages (0.1 iwg)
The VOC Concentration sensor was the RAE Systems ppbRAE.
Accuracy: 3% at calibration point.
--Therefore, 62% and 64% are essentially the same efficiency by the instrumentation used to measure the concentration.   ? ?
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17. Example Data Comparison (3)
Avg = 62%
Avg = 12%
Avg = 64%
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18. Example Data Comparison (4)
Capacity data needs to be normalized
Each filter’s challenge concentration is different
This means the amount of challenge gas to each differs with time.
Solution is to compare capacity at various efficiency points by plotting data as PPB*HR vs Efficiency
Suggested efficiency comparison points.
Higher filter grade  use higher comparison points such as 95%, 90%, 85%, 80%
Lower filter grade  lower comparison points such as 50% and 25%
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19. Normalized Data Comparison (1)
25%
25%
66,420
567,125
832
25%
41,667
717,500
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20. Normalized Data Comparison (2)
Property
Filter X
Filter Y
Filter Z
Test Conditions
Airflow (cfm)
2000
Temp (ºF) 75 77 76
RH (%) 53 46
Challenge Gas
Toluene
Test Results
DP (iwg)
0.64
0.30
0.49
Eff. Challenge (ppb)
368
383
380
Eff. (avg. init.)
62%
12%
64%
Capacity Challenge (ppm)
51.1
49.9
50.0
50% Efficiency
66,420
41,667
25% Efficiency
567,125
832
717,500 
Accuracy for ppm level ~3% FS  1.5 ppm at 50 ppm challenge
50% ppb*hr accuracy is ~2,000 ppbh
25% ppb*hr accuracy is ~20,000 ppbh    
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21. Possible Report Format (1)
Accuracy for ppm level ~3% FS  1.5 ppm at 50 ppm challenge
50% ppb*hr accuracy is ~2,000 ppbh
25% ppb*hr accuracy is ~20,000 ppbh
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22. Possible Report Format (2)
Capacity Test Results can be revised to allow easy comparison from filter to filter.
Summary of Previous Capacity
Information
Easily Comparable Capacity information
at certain efficiency intervals
Example Values
(Not Actuals)
Accuracy for ppm level ~3% FS  1.5 ppm at 50 ppm challenge
50% ppb*hr accuracy is ~2,000 ppbh
25% ppb*hr accuracy is ~20,000 ppbh
NAFA 2015 Technical Seminar

23. NAFA 2015 Technical Seminar
Summary
Gas-Phase filters require a different testing method than particulate filters, ASHRAE 145.2
Key tests performed in the ASHRAE are Pressure Drop, Initial Efficiency, and Capacity
Pressure Drop and Initial Efficiency are simpler to interpret
Capacity Results need to be normalized to compare at the needed performance level.
When the above three key properties are compared, the user can make an educated decision based on application performance needs in conjunction with filter performance and costs.
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24. NAFA 2015 Technical Seminar
References
ASHRAE ANSI/ASHRAE Standard Laboratory Test Method for Assessing the Performance of Gas-Phase Air-Cleaning Systems: Air-Cleaning Devices. American Society of Heating, Refrigeration and Air-Conditioning Engineers, Inc. Atlanta, Ga.
ASHRAE ASHRAE Handbook – HVAC Applications. “Kitchen Ventilation”. American Society of Heating, Refrigeration and Air-Conditioning Engineers, Inc. Atlanta, Ga.
ASHRAE ASHRAE Handbook – Fundamentals. “Air Contaminants”. American Society of Heating, Refrigeration and Air-Conditioning Engineers, Inc. Atlanta, Ga.
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25. Questions? Brad Stanley bstanley@AAFIntl.com
NAFA 2015 Technical Seminar