HEPA Filter Overview

HEPA is an acronym for ‘High Efficiency Particulate Absorbing’ or ‘High Efficiency Particulate Arrestance’ or, as officially defined by the Department of Energy (DOE), ‘High Efficiency Particulate Air.’ This type of air filter can theoretically remove at least 99.97% of dust, pollen, mould, bacteria and any airborne particles with a size of 0.3 micrometres (μm) at 85 litres per minute (Lpm). In some cases, they can even remove or reduce viral contamination. The diameter specification of 0.3 responds to the most penetrating particle size (MPPS). Particles that are smaller or larger are trapped with even higher efficiency. Using the worst case particle size results in the worst case efficiency rating (i.e., 99.97% or better for all particle sizes).

HEPA filters are also employed to filter out highly hazardous aerosols, such as those that are radioactive, bio-hazardous, and highly toxic (e.g. carcinogens). In the event of a nuclear, biological, or chemical outbreak, HEPA filters are the last line of defence between contamination and the those who could be exposed to it.

History of HEPA Filters

The first HEPA filters were developed in the 1940’s by the United States Atomic Energy Commission to fulfil a top-secret need for an efficient, effective way to filter radioactive particulate contaminants. They were needed as part of the Manhattan Project, which was the development of the atomic bomb. The first HEPA air filters were very bulky compared to the HEPA air filters that are produced today. HEPA filter technology was declassified after World War 2 and then allowed for commercial and residential use. The following is a chronological list of events in the history of HEPA filters:

  • Developed during WWII atomic bomb research for containment of radioactive aerosols called ‘superimpingement’ or ‘superinterception’ filters and later referred to as ‘absolute’ filters
  • First prototype filters used esparto grass as the filter medium
  • In the 1950s, glass fibres were introduced into the paper
  • In 1960, the first laminar flow bench was invented at Sandia National Laboratory
  • In the 1960s, specifications were standardized and called HEPA filters
  • In the 1970s, asbestos was removed

Typical Characteristics

At a glance, HEPA filters have the following characteristics:Most submicron semiconductor fabrication lines use Type-D ULPA filters as an improvement over traditional HEPAs for Class-1 and Class-10 environments.
  • Usual size is 3 ft. x 6 ft. x 5.875 in. frame
  • When new, maximum pressure drop is 1 in of water = 0.036 psi
  • Each ft2 of opening corresponds to about 50 ft2 of paper area
  • Designed for 90 lfm air velocity, or 45.7 cm/sec
  • Designed for entraining 500 – 1000 grams of dust per 1000 cfm
  • Are sealed into the ceiling using gel-sealed T-bars
  • Typical lifespan is several years if air is properly prefiltered

Industries and Applications

HEPA air filters have been traditionally used in hospital operating and isolation rooms, pharmaceutical and computer chip manufacturing, as well as in other applications requiring ‘Absolute’ Filtration. Today, HEPA air cleaners, vacuum cleaners, and air filters are used in a wide variety of critical filtration applications in the nuclear, electronic, aerospace, pharmaceutical, and medical fields. HEPA air cleaners, vacuum cleaners, and air filters are required by law to be used in all equipment for asbestos, lead, toxic chemical, and mould abatement. These HEPA filtered products must meet the strict Military Standard 282 HEPA filtration efficiency test.  Today, HEPA filters are used in a broad range of industries including:
  • Microelectronics (e.g. semiconductor clean rooms)
  • Pharmaceutical
  • Bio and gene technology
  • Chemical industry
  • Nuclear air ventilation
  • Waste incinerators
  • Hospital operating rooms
  • Emergency burn centres
  • Cosmetics
  • Medical industry
  • Food industry
  • Optical industry
  • Automotive industry
  • Surface engineering
  • Precision engineering
  • Nano-materials
  • Space industry
  • Military equipment
  • Power and energy plants
  • Controlled and ultraclean environments for critical technologies
  • Movie theatre industry
  • Portable residential air cleaners

Construction and Function

HEPA and ULPA filters are best applied in situations where a high collection efficiency of submicron Particulate Matter (PM) is required, where toxic and / or hazardous PM cannot be cleaned from the filter, or where the PM is difficult to clean from the filter. HEPA and ULPA filters are typically utilized for applications involving chemical, biological, and radioactive PM. HEPA and ULPA filters are installed as the final component in a PM collection system, downstream from other PM collection devices, such as electrostatic precipitately or baghouses (Heumann 1997).

HEPA and ULPA filters are specifically designed for the collection of submicron PM at high collection efficiencies. They are best utilized in applications with a low flow rate and low pollutant concentration. Filter outlet air is very clean and may be re-circulated within the plant in many cases (AWMAI 1992).

They are not sensitive to minor fluctuations in gas stream conditions (Heumann. 1997).

Corrosion and rusting of components are usually not problems. Operation is relatively simple. Unlike electrostatic precipitators, HEPA and ULPA filter systems do not require the use of high voltages; therefore, flammable dust may be collected with proper care (AWMAI 1992).

Filters are available for a range of dimensions and operating conditions. Commercial filter systems and housings are available in several types of configurations to suit a variety of installation and operation requirements. These systems have many built in features such as testing and monitoring equipment. HEPA and ULPA filters are useful for collecting particles with resistivities either too low or too high for collection with electrostatic precipitated (AWMA. 1992).

Unlike bag-houses, which require workers to enter the collector to replace bagel, HEPA and ULPA filters systems are designed to replace filters outside the collector housing. This makes them ideal for applications involving hazardous air pollutants (HAPs) or toxic PM. The collected PM is tightly adhered to the filter media for subsequent disposal. Bag in / bag out procedures that may be required by OHSA are easily performed with the filters (Heumann. 1997).

HEPA Filtration Technical Referances

When designing HEPA filters, there are several items that must be considered: application, environment, efficiency required, physical geometry constraints, structural requirements, system volumetric flow requirements, system operational pressures, existing air handling equipment and its capabilities, as well as maintenance, ergonomics, cost, and manufacturability.

Most HEPA filters are constructed from a mat of randomly arranged special glass fibre sheet pleated in a “V” pattern like a folded paper fan with corrugated aluminium separators between the folds. This is attached to a sturdy base, forming the core of the filter.

HEPA and ULPA filters generally contain a paper media. Newer filter designs may contain nonwoven media, which utilizes recently developed fine fibre technology (INDA, 2000). Generally, the filter media is fabricated of matted glass fibre such as borosilicate microtines (EPA, 1991). The small fibre diameter and high packing density of both the paper and nonwoven media allow for the efficient collection of submicron PM (Gaddish, 1989). The waste gas stream is passed through the fibrous filter media causing PM in the gas stream to be collected on the media by sieving and other mechanisms, as mentioned below. The dust cake that forms on the filter media from the collected PM can increase collection efficiency (EPA, 1998a).

The filter media is pleated to provide a larger surface area to volume flow rate. For this reason, HEPA and ULPA filters are often referred to as extended media filters. Close pleating, however, can cause the PM to bridge the pleat bottom, reducing the surface area (EPA, 1998a). Corrugated aluminium separators are often employed to prevent the media from collapsing (Heumann, 1997). The pleat depth can vary from 2.5 centimetres (cc) (1 in.) up to 40 cm (16 in.). Pleat spacing is generally between 12 to 16 pleats per in., with certain conditions requiring fewer pleats, 4 to 8 pleats per in. (EPA, 1998a).

The most common designs are a box filter cell and a cylindrical filter cell. In a box cell the pleated media is placed in a rigid, square frame constructed of wood or metal. The air flows from the front to the back of the filter. Box packs are approximately 60 cm (24 in.) in height and width and 6 to 30 cm (3 to 12 in.) in length (EPA, 1991). The media in a cylindrical filter cell is supported by inner and outer wire frameworks. A metal cap seals the media at one end. Air flows from the outside to the inside of the filter. This allows a higher air flow rate than a box cell since more surface area is exposed (Vokes, 1999). Typical cylindrical packs are 50 centimetres (cm) (20 in.) in diameter and 35 to 60 cm (14 to 24 in,) in length (Vokes, 1999).

Both the box and cylindrical cells seal the media to the frame or cap using polyurethane, epoxy, or other commercially available adhesive. A metal grill protects the media face from damage. The filter cell is mounted to a holding frame using a gasket or fluid seal. The filter is generally mounted on the clean air plenum (EPA, 1991). The filter can be mounted directly in the duct or in a separate housing. HEPA and ULPA filter systems require pre-filtering for large diameter PM. HEPA and ULPA filter systems are generally the final component in a PM removal system (Heumann, 1997).

The HEPA and ULPA filter cells are generally utilized as a disposable-type filter. As discussed previously, when the filter cake build-up results in unacceptable air flow rates, the filters are replaced. In most designs, replacement of the filter cell takes place at the clean air plenum and outside of the housing unit. This reduces the risk of exposure to PM by the maintenance workers. This feature is especially important. HEPA filters differ in terms of filtration efficiency, configuration (size and shape), materials of construction, and fire resistance.

> Advanced Air Systems

Advanced Air Systems

Terminal Filter

Clean environments often require terminal filters that can be connected directly to the air supply or the planum.

Clean areas such as cleanrooms face a range of filter challenges, including lack of ceiling space, filter maintenance, and filter replacement. Yet with our terminal filters, you need not worry.

Over the past two decades, Filt-Air has delivered large quantities of terminal filters to a range of facilities and industries, including pharma, security, and microelectronics.

The Filt-Air terminal filters provide a range of unique advantages, including:

  • Innovative designs
  • Flexible filter housing sizes
  • Simple-to-replace filters – and simple to access

Fan Filter Unit

Fan Filter Units (FFU) are most frequently seen in cleanrooms, which are actively cleansed, well isolated, and have low concentrations of airborne particles.

The FFU is an essential element in cleanrooms in semiconductor manufacturing, the pharmaceutical industry, scientific research laboratories, and other facilities that require a controlled environment.

The Filt-Air FFU is a combined device within a special housing, which includes a high efficiency filter and a blower, and can also include an electronic controlling system. Multiple FFU devices can be installed on the cleanroom ceiling, in line with the specific requirements of each cleanroom and classification.

When choosing an FFU, it is important to check the following information:

  1. Power consumption and control system
  2. Noise level
  3. Unit heights (especially in low ceiling facilities)
  4. Airflow vs. pressure drop

Fan Filter Unit

Certain extra-precise measuring devices, special engineering machinery, and semiconductor manufacturing areas require the highest level of classification.

Class 1 is considered the cleanest cleanroom, with more than 500 air changes per hour and a ceiling coverage of up to 100%.

For the past two decades, Filt-Air has specialized in developing and manufacturing high-end equipment for Class 1 cleanrooms, for semiconductor industries around the globe, including military systems, measuring equipment, and many other high technology industries.

The Filt-Air FFU for Class 1 cleanrooms is a cutting edge, high technology device, capable of supplying large amounts of filtered air into the required space.

Working Stations

Safe Change Housing (BIBO)

Facilities for dealing with biological, chemical, and radioactive hazardous materials are required to have a safe change housing for the contaminated filters. Such systems are also known as Bag in Bag out (BIBO).

The advantage of the Filt-Air safe change housing system is its proven isolation capabilities during the casual operation and the replacing of decontaminated filters.

Over the years, we have supplied hundreds of BIBO systems for laboratories, BIBO units for nuclear research centers, safe change housing systems for hospitals, and so much more.

Filt-Air provides its customers with customized solutions for varied environments and conditions, using a range of materials (e.g. coated steel, stainless steel 304 or 316), and adapted to any airflow and conditions.

Clean Tent

In some cases, a cleanroom may be required for achieving higher classification of a specific area. Yet building a cleanroom may not always possible (due to lack of space, for example); moreover, specifications may require the installation of a higher classification room within an existing cleanroom. One optimal solution is the building of a Filt-Air clean tent.

This solution includes an FFU system that covers a specific area and has a variety of options for side coverings.

Filt-Air has produced numerous clean tents for the pharma industry, mini-clean environments for the food industry, and even small clean areas for mechanic or electronic assembly. These solutions are tailored to our customers’ specific needs, and can be operated and controlled with the greatest of ease.

Oil Mist Collector

Some CNC machines use oil for cooling and other processes the worked-on surface (such as when milling or drilling). Yet this results in the hazardous dispersion of oil mist into the air – which may then be inhaled by humans nearby. As this poses a serious health hazard, health authorities around the globe have begun to enforce the use of oil mist collectors, to prevent such inhalation.

The innovative Filt-Air oil mist collector has a unique geometric design, to provide excellent separation capabilities and protect CNC operators and other workers in the vicinity – and ensure a safe and healthy workspace.

Panel / Compact Filters

One of the most common air filtration products (high efficiency filtration) are panel filters and compact filters, applied in a variety of industries. These include filters for HVAC, cleanrooms, clean environments, healthcare facilities, laboratories, and more.

Both the panel filter and the compact filter (also known as v-shape or v-bank filter) are based on a pleated structure. It is this structure that allows greater quantities of air to pass through the filter, while reducing pressure and accumulating more dust and particles within the filter due to increase of the filtration area.

The Filt-Air panel filters and compact filters offer customers advantages:

  • Special sizes tailored to your needs. In addition to standard filter sizes, we are able to deliver almost any size required.
  • Precise pleating technology. This unique capability ensures greater efficiency and durability over time.
  • Customized production of filter frames using a variety of materials (including. ABS, coated steel, and stainless steel), latches and handles, to meet specific standards and regulations.

Terminal Filter

Clean environments often require terminal filters that can be connected directly to the air supply or the planum.

Clean areas such as cleanrooms face a range of filter challenges, including lack of ceiling space, filter maintenance, and filter replacement. Yet with our terminal filters, you need not worry.

Over the past two decades, Filt-Air has delivered large quantities of terminal filters to a range of facilities and industries, including pharma, security, and microelectronics.

The Filt-Air terminal filters provide a range of unique advantages, including:

  • Innovative designs
  • Flexible filter housing sizes
  • Simple-to-replace filters – and simple to access

Also referred to as carbon filters, the Filt-Air gas absorption filters prevent penetration of gases into a given space. These gas absorption filters differ from partial filtration solutions (such as Fine Dust, HEPA, and ULPA), as they contain active carbon that can absorb a variety of gases. The filters may contain either granules of active carbon or a combined particle filtration media that is soaked with carbon – to ensure optimal outcomes.

The use of carbon filters is of the utmost importance for industries who deal with harmful gases, including biological institutes, chemistry manufacturers, radioactive research centers, and semiconductor manufacturers. In addition, these are widely used by defense authorities for protection against CBRN threats.

Our main advantage in the field of gas absorption filters is that we are a member of the BE Group, who began their activity in this field more than 50 years ago.

Join our long list of customers around the world who already benefit from Filt-Air products.

Power Stations / Gas Turbines

In today’s world, gas turbines are one of the most widely used power generating technologies. Gas turbines are a type of internal combustion engine, in which the burning of an air-fuel mixture produces hot gases that spin turbines, converting them into power.

As this process consumes huge quantities of air, it needs to be treated properly. Air contains a variety of elements, especially different sized particles – which could affect the efficiency of such power stations or even seriously damage them.

By employing innovative engineering capabilities, Filt-Air’s gas turbine filters enable increased air quantities combined with decreased pressure drops. This is especially important as poor inlet filtration could lead to significant erosion of surfaces (by approx. 10-micron particles), fouling of compressor blades (by 2–10-micron particles), and corrosion due to salts and acids. As such degradation processes are irreversible, they could result in serious damage to extremely costly turbines, while decreasing power generation.

> Filtration Products

Filtration Products

Panel / Compact Filters

One of the most common air filtration products (high efficiency filtration) are panel filters and compact filters, applied in a variety of industries. These include filters for HVAC, cleanrooms, clean environments, healthcare facilities, laboratories, and more.

Both the panel filter and the compact filter (also known as v-shape or v-bank filter) are based on a pleated structure. It is this structure that allows greater quantities of air to pass through the filter, while reducing pressure and accumulating more dust and particles within the filter due to increase of the filtration area.

The Filt-Air panel filters and compact filters offer customers advantages:

  • Special sizes tailored to your needs. In addition to standard filter sizes, we are able to deliver almost any size required.
  • Precise pleating technology. This unique capability ensures greater efficiency and durability over time.
  • Customized production of filter frames using a variety of materials (including. ABS, coated steel, and stainless steel), latches and handles, to meet specific standards and regulations.

Terminal Filter

Clean environments often require terminal filters that can be connected directly to the air supply or the planum.

Clean areas such as cleanrooms face a range of filter challenges, including lack of ceiling space, filter maintenance, and filter replacement. Yet with our terminal filters, you need not worry.

Over the past two decades, Filt-Air has delivered large quantities of terminal filters to a range of facilities and industries, including pharma, security, and microelectronics.

The Filt-Air terminal filters provide a range of unique advantages, including:

  • Innovative designs
  • Flexible filter housing sizes
  • Simple-to-replace filters – and simple to access

Also referred to as carbon filters, the Filt-Air gas absorption filters prevent penetration of gases into a given space. These gas absorption filters differ from partial filtration solutions (such as Fine Dust, HEPA, and ULPA), as they contain active carbon that can absorb a variety of gases. The filters may contain either granules of active carbon or a combined particle filtration media that is soaked with carbon – to ensure optimal outcomes.

The use of carbon filters is of the utmost importance for industries who deal with harmful gases, including biological institutes, chemistry manufacturers, radioactive research centers, and semiconductor manufacturers. In addition, these are widely used by defense authorities for protection against CBRN threats.

Our main advantage in the field of gas absorption filters is that we are a member of the BE Group, who began their activity in this field more than 50 years ago.

Join our long list of customers around the world who already benefit from Filt-Air products.

Power Stations / Gas Turbines

In today’s world, gas turbines are one of the most widely used power generating technologies. Gas turbines are a type of internal combustion engine, in which the burning of an air-fuel mixture produces hot gases that spin turbines, converting them into power.

As this process consumes huge quantities of air, it needs to be treated properly. Air contains a variety of elements, especially different sized particles – which could affect the efficiency of such power stations or even seriously damage them.

By employing innovative engineering capabilities, Filt-Air’s gas turbine filters enable increased air quantities combined with decreased pressure drops. This is especially important as poor inlet filtration could lead to significant erosion of surfaces (by approx. 10-micron particles), fouling of compressor blades (by 2–10-micron particles), and corrosion due to salts and acids. As such degradation processes are irreversible, they could result in serious damage to extremely costly turbines, while decreasing power generation.

Panel / Compact Filters

One of the most common air filtration products (high efficiency filtration) are panel filters and compact filters, applied in a variety of industries. These include filters for HVAC, cleanrooms, clean environments, healthcare facilities, laboratories, and more.

Both the panel filter and the compact filter (also known as v-shape or v-bank filter) are based on a pleated structure. It is this structure that allows greater quantities of air to pass through the filter, while reducing pressure and accumulating more dust and particles within the filter due to increase of the filtration area.

The Filt-Air panel filters and compact filters offer customers advantages:

  • Special sizes tailored to your needs. In addition to standard filter sizes, we are able to deliver almost any size required.
  • Precise pleating technology. This unique capability ensures greater efficiency and durability over time.
  • Customized production of filter frames using a variety of materials (including. ABS, coated steel, and stainless steel), latches and handles, to meet specific standards and regulations.

Terminal Filter

Clean environments often require terminal filters that can be connected directly to the air supply or the planum.

Clean areas such as cleanrooms face a range of filter challenges, including lack of ceiling space, filter maintenance, and filter replacement. Yet with our terminal filters, you need not worry.

Over the past two decades, Filt-Air has delivered large quantities of terminal filters to a range of facilities and industries, including pharma, security, and microelectronics.

The Filt-Air terminal filters provide a range of unique advantages, including:

  • Innovative designs
  • Flexible filter housing sizes
  • Simple-to-replace filters – and simple to access

Also referred to as carbon filters, the Filt-Air gas absorption filters prevent penetration of gases into a given space. These gas absorption filters differ from partial filtration solutions (such as Fine Dust, HEPA, and ULPA), as they contain active carbon that can absorb a variety of gases. The filters may contain either granules of active carbon or a combined particle filtration media that is soaked with carbon – to ensure optimal outcomes.

The use of carbon filters is of the utmost importance for industries who deal with harmful gases, including biological institutes, chemistry manufacturers, radioactive research centers, and semiconductor manufacturers. In addition, these are widely used by defense authorities for protection against CBRN threats.

Our main advantage in the field of gas absorption filters is that we are a member of the BE Group, who began their activity in this field more than 50 years ago.

Join our long list of customers around the world who already benefit from Filt-Air products.

Power Stations / Gas Turbines

In today’s world, gas turbines are one of the most widely used power generating technologies. Gas turbines are a type of internal combustion engine, in which the burning of an air-fuel mixture produces hot gases that spin turbines, converting them into power.

As this process consumes huge quantities of air, it needs to be treated properly. Air contains a variety of elements, especially different sized particles – which could affect the efficiency of such power stations or even seriously damage them.

By employing innovative engineering capabilities, Filt-Air’s gas turbine filters enable increased air quantities combined with decreased pressure drops. This is especially important as poor inlet filtration could lead to significant erosion of surfaces (by approx. 10-micron particles), fouling of compressor blades (by 2–10-micron particles), and corrosion due to salts and acids. As such degradation processes are irreversible, they could result in serious damage to extremely costly turbines, while decreasing power generation.

Thank you for your interest

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