1. NAFA Guide To Air Filtration
Fifth Edition
Chapter 5
HEPA, ULPA and Super ULPA Filters
presented by the
National Air Filtration Association

2. HEPA and ULPA Filters

3. HEPA Filter History
The first HEPA was developed in the 1940’s under a classified government project for filtration of radioactive contaminants.
They were required as part of the Manhattan Project which developed the atomic bomb.
The original filters were quite bulky and inefficient as compared to current HEPA filters. Some had asbestos fibers
After WWII, HEPA filter technology was declassified with commercial manufacturing beginning in the 1950’s.

4. Approx. HEPA Filter Applications in Industry Process/Food/ Optical
Pharm/Biotech/
18%
Aerospace/
Auto 6%
Medical/Hospital
Device
21%
Process/Food/ Optical
24%
Electronics/Micro
31%

5. High Efficiency Particulate (HEPA) Air Filter
“Throwaway extended-medium dry-type filter in rigid frame, when tested at rated airflow having minimum particle-collection efficiency of 99.97% for 0.3 micrometer (µm) mass median diameter particles of DOP when tested in accordance with MIL-STD-282 particles of thermally-generated DOP particles or specified alternative aerosol.”
HEPA’s are made from micro-glass fibers. HEPA filters have a minimum efficiency of 99.97% on 0.3 micrometer particles when tested with thermally generated dioctypthalate (pronounced di-octal-thilate –all “i’s” are long) or any alternative aerosol.

6. HEPA Filter Mechanisms
99.999
0.1
1.0
10.0
0.01
PARTICLE DIAMETER (MICRONS)
99.99
99.97 99 90 50 10
THEORETICAL HEPA FILTER COLLECTION EFFICIENCY
COLLECTION EFFICIENCY%)
HEPA filters also capture higher percentages above and below the 0.3 micrometer size because 0.3 represents the hardest particle to capture as it behaves both like a solid and a gas particle. Many people think that HEPA filters do not capture particles “below” 0.3 micrometers,,,,this slide is show to dispose of that misconception.

7. Components of a HEPA Filter
Media
Separators
Filter pack
Sealant
Framing (cell sides)
Gasketing

8. Wet Laid Glass Fiber Media
Engine Filter-
cellulose paper
HEPA Filter
microglass fibers
HEPA filter media is made like paper is made, by beating glass fibers in a buffered water solution until all are suspended. Binders are added and the mixture is dewatered over a continuous flow screen. The media then dried and rolled.

9. Separator Styles Aluminum Separators
Corrugation heights from .06” to .20” deep
Mini-Pleat
Coated String
Embossed Media
Ribbon of Media
Adhesive Bead
Separators serve several purposes. In HEPA filters with aluminum separators, (usually 6” and 12” thick packs) the separators act to straighten the flow of air through the filter along with holding the pleats apart. In smaller pack variations, the separators just hold the pleats apart.
Minipleat using string separators

10. Filter Sealants
Rubber Based
Urethane
Epoxy
Hot Melt
Silicone

11. Frame Materials Extruded Aluminum Formed Sheet Metal Stainless Steel
Galvanized Steel
Aluminum
Frame Materials
Particle Board
Fire Retardant
Standard
Plywood
HEPA filter framing material

12. Filter Performance
Filter Performance measures penetration (then converted to efficiency)
Most Penetrating Particle Size (MPPS) for differing flow rates
Each filter is tested – (non-destructive test)
It is important to understand that HEPA filter testing determines penetration which is them converted to efficiency. Also, there is a MPPS for different flow rates for all filter materials based on the impingement, interception and diffusion curves and this does apply to HEPA filters.

13. Filter Performance & Application
HEPA
99.97% for 0.3 micron particles MMD (Type A)
99.99% for 0.3 micron particles MMD (Type C)
ULPA
Minimum Particle Collection Efficiency
99.999% Micrometer Particles (Type F)
SUPER ULPA
% on MPPS (Type G)
See page 5.6- for all filter types
IEST now has A-K types of classification of HEPA ULPA and Super ULPA performance. Some on Mass Median Diameter (MMD) particles and some on Most Penetrating Size Particle (MPPS).

14. Gasketing Closed-cell Neoprene Gasket Non-Newtonian Gel Seal
There are two types of gasketing used with HEPA filters…closed-cell neoprene rubber and Non-Newtonian Gel. The closed-cell neoprene gasketing must be compressed to 20 pounds per square inch of gasket area in order to assure a complete seal. The non-Newtonian (this name means it will not drop out of the channel with gravity – Newton’s first law) forms its own gasket. The HEPA has a groove in the face filled with gel and it is set over a knife-edged holding frame. The knife edge penetrates the gel and forms the seal. This is used extensively in cleanroom applications where the weight of the ceiling HEPA presses down on the knife-edge holding device.

15. HEPA Filter Holding Devices
This is a HEPA installed in a HEPA filter holding frame. These frames can be fastened (usually welded) together and configured in whatever needed to meet the CFM needs of the air handler. This filter would normally be found downstream of all fans and blowers in the mechanical room.

16. Terminal HEPA Filters Room-side Replaceable Disposable Terminal
Terminal HEPA filter modules utilizing minipleat technology are increasingly being used in hospital operating rooms because of their positioning at the end of the duct prior to entering the clean area.
Room-side Replaceable Disposable Terminal
Modules Modules

17. Bag In / Bag Out Housing
For highly hazardous filtration, it is necessary that the filter housing be designed to completely contain the filters during changing. This containment system is called Bag In/Bag Out because it utilizes a heavy-duty plastic bag to both remove and install the HEPA and the prefilter. Typical application would be in a Tuberculosis unit at a hospital.

18. Proper Training
Do Not Change Bag In/Bag Out Filters Without Proper Hands-on Instruction, Training, and Accreditation – NAFA Certified Technician, Level II
Proper training is essential so that you do not cause widespread contamination of an area or create a situation that could jeopardize the health of building occupants. NAFA has a special certification for technicians changing bag in/bag out filters called NAFA Certified Technician Level II.

19. HEPA Filter Are Most Always Second or Third Filter Bank
Pre-filtered with Pleat and or MERV 15/16 Filter
Using Neoprene Gasket - Always In Locking HEPA Filter Holding Frame
Using Gel Seal – held in place
Always Exact Size – Not Nominal
Always Requires Special Handling, Installation, and Testing
Slide is self-explanatory – place emphasis on two types of

20. HEPA Filters
No matter where you encounter a HEPA, please remember they stop most all particles of any type and can, under some circumstances, make you ill. Always handle HEPA’s with at least respirator protection.
Because they catch everything, always wear respirator protection when changing any type of HEPA filter

21. Sample Questions
In order to be classified a HEPA filter, the efficiency must be at least?
99.97% on 0.3 micrometer particles
ULPA stands for?
Ultra-Low Penetration Air filter
Two types of gasketing for HEPA’s are?
Closed Cell Neoprene and Non-Newtonian Gel Seal

22. Thank you.
Other Questions?

23. Common Particle Generation
A person simply sitting or standing generates about 100,000 particles per cu. ft.
A person sitting down / standing up generates about 2,500,000 particles per cu. ft.
Walking generates about 10,000,000 particles per cu. ft.
Mild activity generates about 30,000,000 particles per cu. ft.
Industrial processes like grinding, sweeping or welding adds billions of particles per cu. ft.