History of HEPA Update to today Per Lindblom Hollingsworth & Vose April 22, 2010

Presentation Historical review HEPA Filter Media choices Next Generation Micro fiberglass HEPA media

National Defense Research Council Diffusion The National Defense Research Council (NDRC), solicited the assistance of a number of university and industrial scientists in the search for better smoke filters. This effort resulted in important U.S. advances in the theory and technology of aerosol filtration. 1942 Dr. Irving Langmuir developed a general theory for mechanical filtration 1943 LaMer and Sinclair developed instruments to measure the filtration efficiency of DOP smoke (0.30 µm) particles Interception

H&V develops Gas Mask Media The British sent filter paper extracted from captured German gas mask canisters to the U.S. Army Chemical Warfare Service Laboratories (CWS) in the early days of the WW II. NRL analyzed media from a captured German gas mask in early WW II had unusually high particle retention characteristics, acceptable resistance to airflow, good dust storage, and resistance to plugging from oil-type screening smokes. H&V developed US version of this media for gas mask. Media would be known as CWS type 6.

The Collective Protector Gas masks where practical in the field but less so for Army HQ. To address this type of problem, the U.S. Army Chemical Corps developed a mechanical blower and air purifier known as a “collective protector” filter unit. the gas mask canister smoke filter was refabricated into a filter constructed of deep pleats separated by a spacer panel and sealed into a rigid rectangular frame using rubber cement. Picture: PATTON CONFERS WITH EISENHOWER on plan for reduction of Fort Driant. On left is General Patton, on right General Eisenhower.

Manhattan Project In 1942 the top secret Manhattan Project was formed. The Project created potential air pollution problems that could be solved only by using air filters with filter media characteristics similar to those of the CWS filter. The U.S. Army Chemical Corps became the sole supplier of high-performance filters to the Manhattan Project The filters developed in the process was called “superinterception” or “super-efficiency” filters; later referred to as “absolute” filters

Post World War II CWS Filter media relied on raw materials coming from overseas. AEC comissioned Arthur D. Little to find domestic sources. Johns Manville and Owen Corning developed sub-micron diameter glass fibers. 1951 - an all-glass-fiber paper made partly from super-fine glass fibers with diameters substantially less than 1.0 μm. The use of Glass allowed much greater control of manufacturing procedures and production of better, more uniform papers.

The Conception of HEPA 1953 Walter Smith working with Arthur D. Little developed the ‘absolute’ filter for the AEC Arthur D. Little also started the first commercial filter manufacturing company, the Cambridge Filter Company. By 1957, three firms were fabricating absolute filters. In 1960 the first laminar flow bench was invented at Sandia National Laboratory

The Birth of HEPA HEPA filters, an acronym invented by Humphrey Gilbert, from his 1961 AEC report called High-Efficiency Particulate AirFilter Units, Inspection, Handling, Installation. A HEPA filter was defined as a throwaway, dry-type filter with: a minimum particle removal efficiency of 99.95 percent ( which was later raised to 99.97 percent) for a 0.3-μm monodisperse particle cloud; a maximum resistance of 1 inches water gauge (in.wg) when operated at rated airflow capacity a rigid frame

HEPA Filtration enables Technology. 1960’s NASA develops contamination control technology around HEPA filtration after loosing several unmanned satellites. NASA establishes clean room standards for US Manned Space Program in the late 60’s AEC –drives standards and quality control of Filter media Cleanroom Technology enables Lunar Landing Silicon Chips

Evolvement of HEPA Filters Customer demand of higher handling Higher Air volume at a given efficiency. Using less filters in a system Reducing cost.

HEPA Filter Media HEPA media Microfiber Glass PTFE membrane Synthetic Charged Media Nanofibers

Comparison Microfiber Glass vs. Membrane Depth Filters Randomly oriented intertangled fibers laid into a mat. Typically using a Fourdrinier process Submicron glass fibers Glass fiber paper has a very low “solidity” That is, the volume of the sheet contains a low percentage of solid material and a very high percentage of void area. Easy to process PTFE Membrane Surface Filter Biaxially stretched about 800% into a microporous structure. Higher Gamma/Alpha Inert –no outgassing High Cost

Next Generation Microfiber Glass HEPA Filter Media Per Lindblom Paul Smith

PerForm ® Perfect Formation High Performance The importance of Formation will follow High Performance Filter Media 4 -Cost Effective Solutions 15

Evolution of Filter Manufacturer Needs Increasing sophistication of equipment Greater emphasis on productivity Higher pleating speeds Minimize downtime Reduction of waste Minimize filter repairs / touch-ups Reduction in manufacturing variance Improved filter performance Lower pressure drop for a given efficiency/class Hence lower energy demand in usage 16

H&V Product Development Objectives Increase uniformity of fiber distribution Improve processability Elimination of contaminants Reduce variation in media Physical properties Improved Filtration characteristics creating Higher performance Low pressure drop Actions Quantitative measurement of media formation Major capital investments in machine modifications In-line web analysis Defect detecting and tracking Optimisation of the media design 17

Increase uniformity of fiber distribution To improve consistency of pleat shape To improve laminarity of flow through the filter To Increase the filter “gamma” Reduce pressure drop Reduce energy demand Measured and predicted by “Formation Index” 18

Improved Formation: A lower Formation Index is better H&V PerForm HEPA H&V Ashrae Formation Index = 4.0 Typical HEPA Formation Index = 5.2 Typical Ashrae Formation Index = 6.5 19

Formation - Conclusions Formation of the media has significantly improved due to machine and media design changes Lower F.I. means the media has: Fewer Fibre clumps and pills Better overall fiber distribution Minimal air entrapment (air bubbles) Lower F.I. means the media pleats better and results in: Neat sharp pleat tips Even air flow distribution Lower filter pressure drops Higher filter gamma HIGHER PLEATER PRODUCTIVITY 20

Improved Processing Characteristics Typical HEPA Media PerForm ® H&V HEPA Media 21

Improved Performance of the media Gamma = -9.8 . 100 . log Pressure Drop 100 % Pen Gamma is higher when Pressure drop is lower Penetration is lower Two medias, with the same flat sheet gamma: The media with the lower formation index gives Better defined pleat tips and: Higher filter gamma 22

Influence of Formation on filter gamma Two medias with the same flat sheet gamma, one with better formation 23

Improved Flat Sheet Gamma Typical H13/H14 HEPA: Gamma = 12 Pressure Drop (ΔP) = 30.5 mm H2O (max. DOP penetration 0.03%) PerForm ® H13/H14 HEPA: Gamma = 14 10 - 12% lower ΔP for the same efficiency. Pressure Drop (ΔP) = 27 mm H2O (max. DOP penetration 0.03%) 24

Improved Filtration Properties: Gamma Previous Industry standard media H&V media 2007 PerForm media 2009 25

Filter Media 4 cost effective solutions Driven by higher gamma: Both Higher flat sheet gamma Higher filter gamma Filter Design Criteria Longer Life Lower Energy Costs Less Media 26

Filter Media 4 cost effective solutions Design Criteria Longer Life Lower Energy Costs Less Media PerForm ® Lower pressure drop for a given efficiency Cost engineer by removing media area Increase the media face velocity and still meet spec. Still achieve a lower pressure drop for the same efficiency eg. Save 11% of the cost of the media........ 27

Reducing media area 28

Filter Media 4 cost effective solutions Design Criteria Longer Life Lower Energy Costs Less Media Driven again by higher gamma Lower pressure drop means larger delta to the final pressure drop Longer loading time and longer life 29

Every 1 Pa lower pressure drop Filter Media 4 cost effective solutions Filter Design Criteria Longer Life Lower Energy Costs Less Media Energy demand E= (q x Δp)/ η x T x c/1000 e.g 1 Pa, 50% eff, 600x1200mm 0.45m/s, 0.15 USD/kwh -> $0.85 q air flow (m3/sec) Δp average pressure drop (Pa) T running time (hrs) η fan efficiency c cost of energy in USD per kWh Rule of Thumb: Every 1 Pa lower pressure drop Saves $ 1 /yr 30

Filter Media 4 cost effective solutions USD Per Filter ! 31

Filter Media 4 cost effective solutions To summarise Media consistency Minimise defects Measurable F.I. Lower F.I. Redesigned media Higher gamma and Lower pressure drops Productivity improvements Less downtime Less scrap or re-work Faster pleating speeds Filter improvements Sharper pleats Higher flat sheet gamma Higher filter gamma Filter cost savings Cost engineer, Less media Lower energy demand Longer filter life 32

Thank you … Any questions?