1. NAFA Guide To Air Filtration
Fifth Edition
Chapter 8
HEPA and ULPA Filter Testing
presented by the
National Air Filtration Association

2. HEPA Testing Challenge
Has to be non-destructive as each HEPA is individually tested
Should generate an aerosol whose size is MPPS
Monodispersed
Confirm particle size
Measure concentration upstream & downstream of filter
In order for a every HEPA to be challenged, the test must be non-destructive and not affect the performance characteristics of the filter. The best challenge test is one where the aerosol can achieve most penetrative particle size, is monodispersed – that is the particle size is predominately one size, has a way to confirm this size and can measure concentrations upstream and downstream of the filter under test.

3. High Efficiency Filters
HEPA
Minimum Particle Collection Efficiency
99.97% for 0.3 micron particles (Type A)
Penetration Tested
99.99% for 0.3 micron particles (Type C)
Penetration and Leak Tested
ULPA
99.999% For Micron Particles (Type F)
Penetration and Laser Tested
See Page 8.5 for all HEPA Ratings and MOT

4. Efficiency testing Q 107 Hot DOP Penatrometerv o i C l n g V p M / B w A F I k T d E x h u A l t e r n a t e E x h a u s t ( W h e n F i l t e r I s N o t B e i n g T e s t e d )
This schematic shows the working of a Q 107 Hot DOP tester. This device is older technology but still in use today by manufacturers, produced what was thought to be 0.3 micrometer particles by heating DOP as a challenge aerosol. All HEPA filters should be tested with a challenge device before leaving the factory because all HEPA filters are utilized in some kind of critical filtration application.

5. HEPA and ULPA Filter Testing
The Q-107 Penetrometer described in the text was the forerunner of modern testing devices. This picture shows a modern testing apparatus that utilizes a laser spectrometer and polystyrene latex spheres as a challenge aerosol (explain further if necessary).
A modern test device

6. HEPA Filter Testing
Penetration converted to overall efficiency including gaskets, sealing and framing
Initial resistance
Two-Flow Testing - leak test (scanning for leaks)
HEPA filters are encapsulated during testing which means the penetration test not only challenges the media, by the gasket, sealing and cell frame. The test should show initial resistance to airflow and this is used to maintain the appropriate amount of media in the filter to maintain the flow rate of approximately 6 fpm through the filter. Rule of thumb is that initial resistance should be no more than 1” when clean however most HEPA’s have lower initial efficiencies than this. Because a filter may be 99.97% and still have “pinhole” leaks, there has been a two-flow test developed to scan the filter and seal these leaks. This is called a Type B HEPA and the flow rate is reduced to 20% of rated capacity for the leak test. (see page 8.5 for complete list of types and tests)

7. In-place Leak Testing
Done using “cold DOP” or other suitable challenge – it is poly-dispersed
Generator is placed upstream of HEPA filter to introduce challenge particles
Scanning with a
photometer is done
downstream to detect leaks
Cold DOP testing differs from Hot in that cold DOP is poly-dispersed particles over a range of 0.25 to 0.85 micrometers. It is designed to detects leaks in HEPA filter media and gasketing – not determine the efficiency of the filter.

8. Media Damage from Shipping/Handling
Even though HEPA filters are tested at the factory, they must be transported and installed with care. Sometimes this is not done and damage results. This type of damage negates the protection that HEPA’s provide to products, people and the environment. Therefore, critical applications of HEPA filters such as hospitals, isolation rooms and equipment, cleanrooms, and biological facilities and equipment should always be in-place tested using the “cold DOP” protocol. This involves challenging the filter with polydispersed (many sizes) of particles and scanning the filter downstream with a photometer to check for leaks. Small leaks in HEPA filters can be repaired. Tears in the media larger than 1 square inch require the entire filter to be replaced.
In-place scanning of HEPA

9. Mechanical Scan Device at Factory
Some filters that go into cleanrooms cannot be tested with DOP because of possible off-gassing of the chemical. These filters are manufactured in cleanroom environments and challenged with polystyrene latex spheres and leak tested using laser particle counters. Particle counters allow for the sizing and concentration of particles using photomultiplier technology. Certain types of particle counters can count particles in the 2.5 nanometer range = to micrometers.

10. Standards for HEPA Filters
UL 900 – Listed
UL 586 – involves exposing HEPA filter not only to aerosol penetration test, but heated air, moist air, cold air, flame, and others as required by user
IEST – has categorized filter testing for Type A through Type K
HEPA filters come in types A through K and each type is designed to do a different type of application based on efficiency. HEPA filters are classified by UL either by UL 900 just like HVAC filters, or by a more stringent test called UL 586 which requires many more challenges to the filter. IEST has set the types of HEPA filter challenges by type and they are found on page 8.5.

11. Standards for HEPA Filters
EN 1822 – is the European Standard for HEPA and ULPA filters and classifies them from H10-14 for HEPA and U15-17 for ULPA
Factory Mutual – 3rd party testing and verification company
ASME AG-1 (Nuclear applications)
Off-Gassing Qualifications
EN1822:1998 is the European Standard for HEPA and ULPA filters – classification is found on page 8.6 in the text. Factory Mutual is a 3rd party independent testing laboratory that clients can use for HEPA’s and ULPA’s. The American Society of Mechanical Engineers (ASME) AG-1 is the specification for the Design, Inspection and Testing Criteria For Air Filtration and Adsorption Units of Normal Atmosphere Cleanup Systems in Light-water-cooled Nuclear Power Plants. Finally, certain applications as mentioned earlier, require that filters not off-gas any type of particulate or molecular challenge – example is microchip manufacturers.

12. Not On Test But Good To Know Information
Handling HEPA Filters
Limit Handling to Minimum
Use two people to move if >30” high or >36” wide
Do not drop, bump, stack or sit on filters
Do not allow filters to lay flat

13. Not On Test But Good To Know Information
Removing HEPA Filter From Carton
Do not lift filter out of box! Open one end, turn box upside down, lift box off filter
Do not try to remove the filter by lifting it up from the box. You may puncture the media with your fingers
If a filter is equipped with a removal strap, you may carefully use this to remove the filter from the box
When handling, grasp the filter only on outside surface of frame

14. Storage of HEPA Filters
Store filter standing upright on edge so pleats are vertical, not lying flat.
Make sure filters are marked ‘Fragile” and stored in a ‘safe zone’ away from traffic or activity.
Filters <24” under high; stack 3 high. If filters are > 24” high or greater; stack only two high.
Do not expose to dampness, excessive heat or cold (120 degree F. max.), rapidly changing temperature or out of doors.

15. Summary - HEPA Filters
At least 99.97% Efficient on 0.3 micrometer challenge particles
Tested (scan and / or efficiency) using DOP or suitable substitute
Used to filter hazardous materials
Always changed with knowledge and PPE
Used in Bag In/Bag Out application
Should always be handled with care
Read slide and take questions

16. Sample Questions Minimum efficiency for filter to be a HEPA?
99.97% on 0.3 micrometer particles
European Standard for HEPA and ULPA filters is?
EN1822
Difference between Hot DOP and Cold DOP is?
Size of particle challenge
Testing HEPA filters after installation is called?
In-place Leak Testing or Cold DOP Test

17. Thank you.
Other Questions ?