ASHRAE Journal - May 2013 - 85

MERV
Standard 52.2

Intended Dust
Spot Efficiency
Standard 52.1†

1 to 4

<20%

5 to 8

<20 to 60%

9 to 12

40 to 85%

13 to 16

70 to 98%

17 to 20*

Removed from Standard

Average Particle Size
Arrestance
Ranges
60 to 80%

>10.0 mm

Typical Applications

Typical Filter Type

Residential/Minimum; Light/
Commercial; Minimum/
Equipment Protection

Permanent/Self Charging (Passive);
Washable/Metal, Foam/Synthetics;
Disposable Panels; Fiberglass/Synthetics

Industrial Workplaces;
Pleated Filters; Extended Surface
Commercial; Better/Residential;
Filters; Media Panel Filters
Paint Booth/Finishing
Superior/Residential; Better/
Non-Supported/Pocket Filter/Rigid Box;
>90 to 98%
1 to 3 mm
Industrial Workplaces;
Rigid Cell/Cartridge
Better/Commercial Buildings
Smoke Removal; General Surgery;
Rigid Cell / Cartridge; Rigid Box/Non>95 to 99% 0.30 to 1 mm Hospitals & Health Care; Superior/
Supported/Pocket Filter
Commercial Buildings
80 to 95%

3 to 10 mm

Clean Rooms; High Risk Surgery;
Hazardous Materials

HEPA; ULPA

This table is intended to be a general guide to filter use and does not address specific applications or individual filter performance in a given application. Refer to manufacturer test results for additional information. *ASHRAE does not have a test procedure for HEPA testing and has dropped the MERV 17 to 20 classifications; †ANSI/ASHRAE
Standard 52.1 ranges are provided for reference only. Standard 52.1 was discontinued as of January 2009.

Table 2: Table 1 from NAFA User’s Guide for ANSI/ASHRAE Standard 52.2-2007.
May 2013

ASHRAE Journal

85

Source: American Cleanroom Systems

for leak-testing HEPA and ULPA filters in the
Maximum Particles/m3
Federal
factory as they are produced, at the job site
Standard 209E
Class
≥0.1 mm ≥0.2 mm ≥0.3 mm ≥0.5 mm
≥1 mm
≥5 mm
Equivalent
before they are installed, and after they are
ISO 1
10
2
installed in cleanrooms and in unidirectionalISO 2
100
24
10
4
flow, clean-air devices. The scope further sugISO 3
1,000
237
102
35
8
Class1
gests that the RP be used to define the basis of
ISO 4
10,000
2,370
1,020
352
83
Class10
the specification of HEPA and ULPA filters,
ISO 5
100,000 237,000 102,000
35,200
8,320
293
Class 100
and in the testing of unidirectional-flow,
ISO 6 1,000,000 237,000 102,000
35,200
8,320
2,930
Class1,000
clean-air devices and cleanrooms.
ISO 7
352,000
83,200
2,930 Class 10,000
ISO 8
3,520,000
832,000 29,300 Class 100,000
Selecting a filter to meet a certain MERV reISO 9
35,200,000 8,320,000 293,000
Room Air
quirement does not specify the maximum allowable leakage for a filter installed in a device and Table 1: ISO 14644-1 cleanroom standards.
by adding the requirement of IEST-RP-CC034.3
to a specification, the design engineer has covered the maximum al- dropped in 2001 in favor of ISO 14664.
lowable leakage that is allowed in the test procedure. In most cases,
When calling for the required MERV on a project, the design
the air-distribution device will require an adequate seal or gasket, engineer should also state at which Standard 52.2-2012 velocifor example, a gel seal, to meet the minimum leakage requirements. ties the MERV is required. For example, the engineer can require
a MERV 15 at a velocity of 630 fpm (3.20 m/s).
Summary and Guidelines
HEPA and ULPA filters with MERV greater than 16 are no lonDesigners are required to comply with applicable county, ger addressed in Standard 52.2-2012. IEST-RP-CC001.5 outlines
state, or federal codes, and the IEST Recommended Practices the performance of HEPA and ULPA filters. The specification of
covering HEPA and ULPA filters are often referred to in industry the required filter efficiency may not be met if the filter is installed
guidelines for the design of critical environmental spaces. For in a device. IEST-RP-CC034.3 covers definitions, equipment, and
example, the 2007 Minimum Design Standard for Health Care procedures for leak-testing HEPA and ULPA filters in the factory
Facilities in Michigan refers to IEST for filter testing that are as they are produced, at the job site before they are installed, and
not covered by Standard 52.2-2012. Note: Revised editions of after they are installed in cleanrooms and in unidirectional-flow,
IEST-RP-CC001 and CC034 are expected to be published later clean-air devices. Units that meet this RP are typically provided
this year. Check for any changes in requirements.
with gel seals rather than gasket seals.
Engineers designing critical environmental applications
such as cleanroom and surgical suites may consider using the Acknowledgments
definitions as outlined in ISO 14644-1, the current recognized
The author would like to thank Don Bailey, P.E., senior mestandard for the classification of cleanrooms (Table 1). Although chanical engineer, TLC Orlando, and R. Vijayakumar, Ph.D.,
it is common in our industry to classify rooms such as “Class with Aerfil for their contribution to this article.
100” or “Class 10,000,” this classification system, originally
David A. John, P is general manager, vice president of ADE
.E.,
developed and maintained by the GSA FED-STD-209E, was Engineered Solutions of Florida, in Orlando, Fla.



ASHRAE Journal - May 2013

Table of Contents for the Digital Edition of ASHRAE Journal - May 2013

ASHRAE Journal - May 2013
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
VAV Reheat Versus Active Chilled Beams & DOAS
A Stable Whole Building Performance Method for Standard 90.1
Technology Award Case Studies:
PSU Design Build Project
Passive Cooling for School
Standing Columns
Building Sciences
InfoCenter
Refrigeration Applications
IAQ Applications
Engineer's Notebook
Products
Data Centers
Emerging Technologies
Classified Advertising
Advertisers Index
ASHRAE Journal - May 2013 - ASHRAE Journal - May 2013
ASHRAE Journal - May 2013 - Cover2
ASHRAE Journal - May 2013 - 1
ASHRAE Journal - May 2013 - 2
ASHRAE Journal - May 2013 - Contents
ASHRAE Journal - May 2013 - Commentary
ASHRAE Journal - May 2013 - 5
ASHRAE Journal - May 2013 - Industry News
ASHRAE Journal - May 2013 - 7
ASHRAE Journal - May 2013 - 8
ASHRAE Journal - May 2013 - 9
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ASHRAE Journal - May 2013 - 12
ASHRAE Journal - May 2013 - 13
ASHRAE Journal - May 2013 - Letters
ASHRAE Journal - May 2013 - 15
ASHRAE Journal - May 2013 - Meetings and Shows
ASHRAE Journal - May 2013 - 17
ASHRAE Journal - May 2013 - VAV Reheat Versus Active Chilled Beams & DOAS
ASHRAE Journal - May 2013 - 19
ASHRAE Journal - May 2013 - 20
ASHRAE Journal - May 2013 - 21
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ASHRAE Journal - May 2013 - A Stable Whole Building Performance Method for Standard 90.1
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ASHRAE Journal - May 2013 - InfoCenter
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ASHRAE Journal - May 2013 - Refrigeration Applications
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ASHRAE Journal - May 2013 - IAQ Applications
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ASHRAE Journal - May 2013 - Engineer's Notebook
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ASHRAE Journal - May 2013 - Data Centers
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ASHRAE Journal - May 2013 - Emerging Technologies
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