Camfil Farr Product Catalog - Texas Air Products

Air Filter Technology
Product Performance Barometers
ASHRAE Standard 52.2-2007
In ASHRAE Standard 52.2-2007, an air filter’s performance is
determined by measuring the particle counts on both the upstream and
the downstream of the air filter device being tested. The filter user is
then provided capture efficiency values throughout a range of particle
sizes, allowing them to be specific in selecting a filter that has the best
efficiency for the contaminant they want to remove.
If a user wants to remove paper dust in a bill processing facility, they
can select a filter with a high efficiency specific to the relatively large
size of that contaminant. If the contaminant of concern is tobacco or
welding smoke, they can select a filter specific to the much smaller size
of that contaminant. Each manufacturer should be able to provide a
graph for each product that shows that product’s capture efficiency
through the twelve individual particle size ranges of the test.
To simplify filter selection, the Standard defines a minimum efficiency
reporting value (MERV). The MERV is a single number that simplifies the
filter selection process by providing the specifier, or the user, a single
value of specification for filter selection. For most filters that use
mechanical principles of filter operation, this number will most likely be a
minimum value at installation and throughout the life of the filter.
Particle Size Ranges
of Standard 52.2-2007
11
Range
Lower Limit
(microns)
Upper Limit
(microns)
1 0.30 0.40
2 0.40 0.55
3 0.55 0.70
4 0.70 1.00
5 1.00 1.30
6 1.30 1.60
7 1.60 2.20
8 2.20 3.00
9 3.00 4.00
10 4.00 5.50
11 5.50 7.00
12 7.00 10.00
Conover NC, Corcoran CA, Crystal Lake IL, Riverdale NJ,
Washington NC, Laval Quebec, Concord Ontario
United States Tel: (866) 422-6345, Canada Tel: (800) 976-9382
www.camfilfarr.com
Unfortunately, filters that use the principle of electrostatic attraction can
‘fool’ the test by providing a high MERV during the test, but due to the
loss of electrostatic attraction during operation, a much lower value
during application. The user may not be getting the particle removal
efficiency that they originally specified.
Multiple studies have shown that coarse fiber media (charged synthetic
media), unlike fine fiber media (fiberglass media), perform differently in
real-life applications. Coarse fiber media depends on an electrostatic
charge to achieve the published filter efficiency. As atmospheric air
passes through the filter, with 99% of the particulate less than 1.0
micron in size, this very fine particulate will dissipate the charge, and the
filter quickly loses efficiency.
In January 2008, the ASHRAE Standards Committee, charged with
reviewing and improving the ASHRAE 52.2-2007 test standard for air
filters and air cleaners, initiated a change to address this problem.
Appendix J incorporates a non-mandatory filter-conditioning step to
replace the 30 grams loading of ASHRAE dust that was defined in
ASHRAE 52.2-1999 as the conditioning step. The revised standard will
challenge the filter using a KCl (potassium chloride) conditioning method
that closely mimics the aerosol size particle distribution that air filters
will commonly experience when operated in “real-life” conditions.
This will provide air filter users and specifiers an additional value so they
can further ensure the filter’s performance for the intended application.
Filters that use fine fiber media operate on mechanical principles of
particle removal, including impingement and diffusion. They do not lose
efficiency over time, and typically, their rated MERV will be the MERV
obtained when testing, using the optional method in Appendix J.
The user or specifier may take comfort that the published efficiency of
the filter will be consistent throughout the life of the filter.
Importance of Change
The Appendix J conditioning step will allow manufacturers to show both
test procedure results on reports and product literature. Users can
access this information, or have filters tested at independent test
laboratories, to judge air filter selection and specification for optimum
air quality and equipment protection.
ASHRAE Research Project 1189 showed that using the KCl conditioning
step closely replicated real-life filter performance. Thus, in the revised
standard, if a filter shows a different MERV value between the standard
test and the optional Appendix J test, it is safe to assume the Appendix J
rating will be closest to the actual efficiency performance value the filter
will deliver in real-life application.
As part of our program for continuous improvement, Camfil Farr reserves the right to change specifications without notice.