1. Challenges Evolving from ASHRAE 52.2 Test Method
T.J. Ptak
Presented at
National Air Filtration Association, TECH 2013

2. ASHRAE 52.2 – Conditioning method Conclusions
Scope
Introduction
Test methods
ASHRAE 52.2 test method
Current variability
Potential causes of variability
ASHRAE 52.2 – Conditioning method
Conclusions

3. General Requirements Definition (ASTM) Test Method
“Definitive procedure for the identification, measurement, or evaluation of one or more qualities, characteristics, or properties of a material, product, or system”
General Requirements
Test method must measure characteristic or property that will predict usefulness of a product when it is put to its intended use
Test method is supposed to predict performance in later stage in the life of a material or product

4. Main Components and Steps
Test Method
Main Components and Steps
Test procedures
Test method tolerances
Reducing variability
Determine sources of unnecessary variability
Ruggedness test
Procedure for interlaboratory testing
It is not for detecting and eliminating sources of variability
Precision and bias

5. ASHRAE 52.2 – Performance Characteristics
Test standard – ASHRAE 52.2
Differential pressure
Fractional efficiency for particle size range 0.3 – 10 µm
Initial, intermediate and final
Dust holding capacity at specified terminal ΔP
Reporting
PSE curve after each step of dust loading
Develop a composite minimum efficiency curve
Report average E1 0.3 – 1.0 µm
E – 3.0 µm
E µm
MERV - Minimum Efficiency Reporting Value

6. Differential pressure + Efficiency
ASHRAE 52.2 –Check List
Differential pressure +
Efficiency
Initial
Intermediate +/-
Final /-
Filter life
Tolerances -
Process to reduce variability - (+)
Precision and other statistics -

7. ASHRAE 52.2 – Current Situation
Round Robin Test – report issued in 2005
1088-RP – Coordinate and Analyze Interlaboratory Testing of Filters under ASHRAE 52.2
Differences between laboratories
Differences still exist
SSPC 52.2 activities

8. ASHRAE 52.2 – Round Robin Test
Round Robin Test sponsored by ASHRAE*
Participating labs 8
Selected filters 4
Type 1 – 24 x 24 x 12” glass (MERV 10-11)
Type 2 – 24 x 24 x 4” electret (MERV 8-11)
Type 3 – 24 x 24 x 4” cotton/PET (MERV 5-7)
Type 4 – 24 x 24 x 12” electret (MERV 15-16)
Filters were pre-tested at independent lab
Statistical methodology
Repeatability – precision of the method within a given lab
Sr – repeatability standard deviation
Reproducibility - precision of the method when comparing labs
SR – reproducibility standard deviation
NOTE: * from ASHRAE 1088-RP

9. ASHRAE 52.2 – RRT Variability
Round Robin Test results
Precision statistics for pressure drop measurement
Repeatability CV 1.8 – 6.7%
Reproducibility CV 5.3 – 6.8%
Precision statistics for weight gain
Repeatability CV 7.5 – 26.5%
Reproducibility CV 8.1 – 26.5%
MERV summary
Type 1 (1st stage) MERV 11 (5); MERV 10 (1)
Type 2 MERV 8 (9); MERV 10 (1); MERV11 (2)
Type 3 MERV 5 (1); MERV 6 (10); MERV 7 (1)
Type 4 MERV 14 (4); MERV 15 (8)

10. ASHRAE 52.2 - RRT Variability
Round Robin Test results
Precision statistics for Type 4 filters
Repeatability Sr E1 – 1.71; E2 – 0.50; E3 – 0.0 Reproducibility SR E1 – 2.63; E2 – 0.93; E3 – 0.41
Precision statistics for Type 3 filters
Repeatability Sr E1 – 1.91; E2 – 2.42; E3 – 3.94 Reproducibility SR E1 – 2.61; E2 – 3.88; E3 – 4.98
Precision statistics for Type 2 filters
Repeatability Sr E1 – 2.86; E2 – 4.99; E3 – 2.45 Reproducibility SR E1 – 5.00; E2 – 6.05; E3 – 3.04
Calculated 95% confidence interval for individual results
“2 Sr “ = 1.96 Sr
“2 SR ” = 1.96 SR

11. ASHRAE 52.2 – RRT Variability
What does it mean for filter users?
Pressure drop
Filter Type 2 Type 3 Type 4
Average ΔP, [in. H2O]
95% Confidence, 2 SR ± ± ±0.11
95% Confidence range – – – 0.87
Dust holding capacity
Filter Type 2 Type 3 Type 4
Average DHC, [gram]
95% Confidence, 2 SR ±32 ±44 ±72
95% Confidence range 165 – – – 210

12. ASHRAE 52.2 – RRT Variability
What does it mean for filter users?
Filter Average efficiency
Type 2 E1=19 E2=57 E3=82
95% Confidence, 2 SR
95% Confidence range 2 – – – 88
MERV >50 >85
MERV >65 >85
Is the current situation acceptable?
Statistical evaluation can not be applied to MERV
Report was published in 2005
ASHRAE SSPC 52.2 activities
Significant variability still exist

13. ASHRAE 52.2 - Potential Sources of Variability
General requirements:
Test duct configuration
Specified dimensions, locations of measuring points, transitions
Straight test duct, U - shaped
Particle counters
Optical particle counter, (OPC)
Aerodynamic particle counter, (APC)
Other test instruments
Pressure gauges manometer
Flow meter ASTM nozzle
Aerosol generation atomizing nozzle
Dust feeder

14. ASHRAE 52.2 - Potential Sources of Variability
General requirements:
Recommended range of flow rate
472 – 2990 cfm
Air velocity 118 – 748 fpm
Air velocity 492 fpm if not specified (for residential 295 fpm)
Recommended range for temperature and relative humidity
T = 50 – 100oF
RH = 20 – 65%
Challenge aerosol
KCl
Loading dust
ASHRAE dust (75% - SAE J726 dust; 23% powdered carbon; 5% milled cotton linters)

15. ASHRAE 52.2 – Residential Filtration
Test method is not applicable to:
Electrostatic precipitators
Hybrid filters with external electrostatic field
Selection of the air velocity – historical approach
1 inch deep filters tested at 295 fpm
4 inch deep filters tested at 492 fpm
Confusion with claims and test results
Claims for 1 inch filters based on V = 295 fpm
Claims for 4 inch filters based on V = 492 fpm

16. ASHRAE 52.2 - Performance of Selected Filters
Filter dimensions 20 x 25 x 4 and 20 x 25 x 1in.
Filter pressure drop
Q=1024 cfm Q=1708 cfm

17. ASHRAE 52.2 - Performance of Selected Filters
Filter dimensions 20 x 25 x 4 and 20 x 25 x 1in.
Filter efficiency at 1200 cfm

18. ASHRAE 52.2 - Performance of Selected Filters
Filter dimensions 20 x 25 x 4 and 20 x 25 x 1in.
Filter efficiency at 2000 cfm

19. Sources of Variability – Filter Pressure Drop
Pressure drop data from RRT
Filter Type 2 Type 3 Type 4
Average ΔP, [in. H2O]
95% Confidence, 2 SR ± ± ±0.11
95% Confidence range – – – 0.87
Temperature and relative humidity range
Potential sources of variability
Pressure drop across empty section ΔP<0.03” wg.
Pressure drop gauge accuracy ±2.5% (?)
Differential pressure transducers are used for convenience
Generally it is ±0.25% of full scale
For gauge 0 -10” wg. range ±0.025” wg.

20. Sources of Variability – Filter Pressure Drop
Measurement of flow rate
ASME long-radius nozzle
Uncertainty of ±2% for nozzles with beta =
Surface finish 16 RMS (16 micro inches)
Calibrated nozzle can have accuracy as low as ±0.25%
Required input – temperature, air density, pressure
Laminar flow elements are used flow measurements
Better accuracy, generally 0.8% of reading
LFE with accuracy =1% and flow rate Q=2000 cfm
Flow measurement accuracy is ± 20 cfm → ΔP > 0.01” wg
Pressure drop measurement across ASME nozzle
No information on filter pressure drop at high elevation, correction for temperature, humidity

21. Sources of Variability – Filter Efficiency
Temperature and relative humidity range
Impact of relative humidity on particle size
Particle counters
Optical particle counter
Flow rate 0.1 cfm; ±2%
< 10% coincidence error at 300,000 particles/min
Aerodynamic particle counter
No requirements
Aerosol neutralization
Radioactive (beta or gamma) with activity >5 mCi
Corona discharge with 3 µA current
Annual measurement of activity is recommended

22. Sources of Variability – Filter Efficiency
Dust migration after dust loading
Airflow for 20 minutes
Duration less than 20 minutes is allowed if release rate <5%
Potential duct contamination due to dust loading
Dust loading is sometimes performed in a different test duct
Potential particle settling at low air velocity
Issues with statistical evaluation
Ruggedness Tests could find variables that strongly influence measurements

23. Sources of Variability – Dust Holding Capacity
Filter Type 2 Type 3 Type 4
Average DHC, [gram]
95% Confidence, 2 SR ±32 ±44 ±72
95% Confidence range 165 – – – 210
Temperature and relative humidity range
Test dust and filter components are to some degree hygroscopic – increase weight when exposed to high RH
Size distribution of ASHRAE dust
Potential difference between filter and dust loaded in two different test rigs

24. ASHRAE Conditioning
Initial conditioning with a dust loading of 30 grams or increase pressure drop by ΔP=0.04” wg.
Real life test data for filter efficiency made of some electrostatically enhanced media is lower
Research has been initiated to simulate this behavior
ASHRAE 1190-RP – Develop a New Loading Dust
Other conditioning methods:
Exposure to diesel soot
Exposure to cigarette smoke
Exposure to ultrafine particles
Exposure to alcohol (spray, dip, vapor)
Conditioning = removal of electrostatic enhancement?
Conditioning = simulation of real life performance?

25. Impact of the initial loading on efficiency
ASHRAE Conditioning
Impact of the initial loading on efficiency

26. How do other organizations test filters?
NIOSH - Conditioning
How do other organizations test filters?
National Institute for Occupational Safety and Health (NIOSH)
Procedure for testing particulate respirators – 42 CFR 84 regulation
3 types of class of filters:
Class Agent Load Particle size
N-Series NaCl 200 g 0.3 µ
R-Series DOP oil 200 g µ
P-Series DOP oil stabilized 0.3 µ

27. Loading with NaCl particles using TSI 8130
NIOSH - Conditioning
Loading with NaCl particles using TSI 8130
After alcohol
P=50%
After alcohol P= 30%

28. MERV 15 filter tested at 492 fpm
ASHRAE Conditioning
MERV 15 filter tested at 492 fpm
Electrostatically enhanced material
Field test data Different conditioning process

29. ASHRAE 52.2 - Conditioning High Efficiency Electrets
Performance after loading with cigarette smoke, combustion particles and real life
Initial Efficiency at 0.3 µm particles, E >99.99%
Treatment Efficiency, [%]
12 months real life
300 cigarettes >99.97
Diesel soot (60 min)at 450 µg/m3 >99.97
What would be efficiency of this filter after alcohol ?

30. Conditioning with UFP particles (ASHRAE 52.2 J)
ASHRAE 52.2 – Conditioning
Exposure to alcohol
Limitations:
Does not simulate real life
Can not be applied to filters with external electric field
Can not be applied to gas phase filters, PCO, UV
Can affect filters with surface tackifiers
Can affect high efficiency electrets
Conditioning with UFP particles (ASHRAE 52.2 J)
Eliminates all the above concerns
Test method requires some improvements to reduce variability

31. ASHRAE 52.2 – Conditioning App. J
ASHRAE 52.2 Appendix J (1190-RP)
Size distribution of challenge aerosol - number

32. ASHRAE 52.2 – Conditioning App. J
Ambient aerosol – size distribution

33. ASHRAE 52.2 - Conditioning App. J and Field Test
Can mechanical media be affected by conditioning
Field test and conditioning – high efficiency mechanical
Field test Conditioning

34. ASHRAE 52.2 - Conditioning App. J and Field Test
Can mechanical media be affected by conditioning
Field test and conditioning – high efficiency electret
Field test Conditioning

35. ASHRAE 52.2 - Conditioning App. J and Field Test
Can mechanical media be affected by conditioning
Field test and conditioning – MERV 8 mechanical
Field test Conditioning

36. ASHRAE 52.2 – Conditioning Summary
Conditioning method according to the ASHRAE 52.2 Appendix J should be used in filter testing
Simulates better real life performance
Requires some improvements
Flat sheet test of filter media according to this test method is an inexpensive and not time consuming
Alcohol treatment should be used only to determine if filter material poses an electrostatic charge
Severely overestimate performance degradation

37. Variability of the ASHRAE 52.2 test method is not acceptable
Conclusions
Variability of the ASHRAE 52.2 test method is not acceptable
Results from Round Robin Test and other Research Projects (PR) were never implemented
Reproducibility
Some variability sources could be quickly evaluated by conducting Ruggedness Tests
Conditioning test method according to the Appendix J should be improved and adopted as a test method