1. Nafa Tech Seminar Phoenix Arizona 2004
Phil Maybee
NAFA President
the filter man

2. MERV
A practical look at ASHRAE 52.2 “Method of testing general ventilation air-cleaning devices for removal efficiency by particle size”

3. Definition Minimum – worst case scenario
Efficiency – based upon specific particle size challenge
Reported –12 sets of particle sizes in three groups of four sets to make ranges E-1,2,3
Value – tested upstream vs downstream and given as a percentage performance

4. WHY MERV ASHRAE 52.2 ASHRAE 52.1 Particle size performance
Minimum efficiency
Tested to maximum airflow advertised
Tested to realistic pressure drops
Consistent test aerosol
ASHRAE 52.1
Dust spot efficiency
Average efficiencies
Moving pressure drop values
Atmospheric challenge changes
Dust Holding Capacity

5. ASHRAE 52.2 Test Duct Configuration
Outlet
Filters
ASME
Nozzle
Downstream Mixer
Exhaust
Room Air
OPC
Inlet
Filters
Aerosol
Generator
Upstream
Mixer
Device
Section
Blower
Flow
Control
Valve
Backup Filter
Holder (Used
When Dust loading)

6. Possible downside?
ASHRAE 52.2 uses Neutralized dust meaning that the natural positive and negative charges in the atmosphere are diminished in the test
This could have a different effect on efficiency compared to natures effects

7. Average Efficiency? When it does not work!! (new)
When is a 95% filter not a 95% filter?
When it does not work!! (new)
the top five 95% V-cell filters today have an initial efficiency of 57 – 81% on their best distributed test report

8. Determine the NEED
The particle size which causes problems varies from industry to industry and methods or purpose of use
Once we determine the particle size we can choose a filtration efficiency - MERV

9. WHO Sets the Particle Size?
Industries that know what the killer defect size particle is, require filtration systems to remove those particles from the air…
Paint finishes
Computer chip manufacturing
Bio/Genetic research
Surface Etching

10. Ranges in 52.2 Testing E-3 particles between 3 and 10 microns
(efficiency is calculated on the composite range)
NOTE: there is no mathematical correlation between 52.1 and 52.2 filter efficiencies

11. MERV Data

12. MERV 1 - 4
Filters that fit within the category are not tested by ASHRAE 52.2 test procedure. Rather the Standard refers them back to ASHRAE 52.1
Less than 20% Efficient on the E-3 range
These are the historic arrestance type filters – autorolls, metal washables, etc

13. MERV 5 - 8 Starting above 20% on the E-3 range MERV 5 must be 20-35%
MERV 8 must be above 70%
Can be Filters from 20% to 60% Dust Spot

14. MERV
Measurable efficiency on the E-2 Range and a minimum of 85% or more on E-3
MERV 9 must be up to 50%
MERV 10 must be 50-65%
MERV 11 must be 65-80%
MERV 12 must be more than 80%
(filters can be from 40 – 90% Dust spot)

15. MERV
Measurable efficiency in submicron E-1 and more than 90% in the E-2 and E-3
MERV 13 is up to 75%
MERV 14 must be 75-85%
MERV 15 must be 85-95%
MERV 16 must be more than 95% in all categories E-1, E-2 and E3
(can be filters from 75 Dust spot – 95 DOP)

16. MERV Reporting A filter is given a MERV at a given airflow Example :
MERV 11 at 492 fpm
(1968 cfm)
MERV 11 at 295 fpm
(1180 cfm)

17. MERV Reporting Final pressure drops are per Range E-3 is 0.6” wg
Dust Holding Capacity is not a reported value

18. What does the 52.2 Provide
“When a specific particle size efficiency is identified as the target particle size it is possible to look at the test for that specific size rather than depend on the MERV”

19. TYPICAL 52.2 COMPLETE LOADING TEST DATA REPORT
Size Range (microns)
Fractional Efficiency P (“W.G.)
Composite Minimums
0.285
0.320
0.464
0.643
0.822
1.000
2.7
6.7
17.2
29.4
37.1
37.9
2.7
7.8
15.9
27.7
43.3
53.2
54.6
7.8
11.2
30.2
46.0
60.7
70.5
71.6
11.2
17.6
42.6
59.3
73.7
81.3
81.8
17.6
20.4
51.6
70.3
80.8
83.7
85.2
20.4
23.9
58.2
76.5
84.7
86.1
87.2
23.9
28.3
69.9
84.1
89.1
90.2
91.0
28.3
36.3
83.9
91.9
94.2
94.4
93.2
36.3
39.4
89.4
93.7
95.8
96.4
94.9
39.4
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.
42.8
90.6
95.3
96.5
97.9
95.6
42.8
46.5
92.3
97.1
98.0
98.4
97.9
46.5
50.4
94.8
97.5
98.3
100.0
99.2
50.4
Initial
Minimum Efficiency Reporting Value: MERV
0.3 to 1.0 Micron
1.0 to 3.0 Micron
3.0 to 10.0 Micron
Composite Average Efficiency:
E1 = 9.8
E2 = 27.2
E3 = 44.8

20. 52.2 Users Guide Simple explanation of test procedure
Has all the ranges and particle size info
Rough equations to 52.1 efficiency
And examples of the uses