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Selection of HEPA, Medium Efficiency Filter & Pre Filter for Air Purification Equipment

Author: Shenzhen ZhongJian South Environment CO., LTDissuing time:2021-12-29 17:11:14Pageviews:154smallinBig

How to choose the suitable air filter for purification equipment? What is the difference between pre filter, medium efficiency filter and HEPA filters? How to distinguish?
Text label:HEPA, Selection of air filter, Pre Filter, Air filter

1. Pre Filter

      There are four styles of pre filter: panel filter, pleated filter, bag filter and box type filter. The outer frame materials include paper frame, aluminum alloy frame, galvanized iron frame, stainless steel frame, and the filter material includes non-woven fabric, nylon mesh, and activated carbon filter, metal mesh, etc., the protective net has double-sided plastic-sprayed wire mesh and double-sided galvanized wire mesh. Low price, light weight, good versatility and compact structure.

  1.1 The application of pre filter:

      The pre filter is suitable for central air conditioning and centralized ventilation system filtration; large-scale air compressor filtration; clean return air system; the pre-filter system of medium-efficiency and high-efficiency filtration device, AHU, etc.


2. Medium Efficiency Filter

  2.1 Key of medium-efficiency filter selection

      2.1.1 The main control parameters selected medium-efficiency air filter are filtration efficiency, initial resistance, dust holding capacity and overall dimensions under rated air volume., etc.

      2.1.2. In accordance with the method specified in JG/T22-1999 "General Ventilation Air Filter Performance Test Method", the air dust counting efficiency for particles with a particle size of ≥1.0μm is ≥20% and filters with <70% are medium-efficiency air filter.

      2.1.3. Commonly used filter materials for medium-efficiency air filters include glass fiber and non-woven fabrics.

      2.1.4. The manufacturer shall provide the dust holding capacity of the filter.

      2.1.5 The initial resistance of the medium-efficiency air filter should be ≤80Pa. When designing, the resistance of the filter can be calculated based on twice the initial resistance as the final resistance.  

      2.1.6 The initial resistance of the filter shall not exceed 10% of the resistance of the product sample. After regenerating and cleaning the renewable or washable filter media, the efficiency should not be lower than 85% of the original index, and the resistance should not be higher than 115% of the original index.

      2.1.7 The air filter should meet the fire protection requirements, and the flash point of the paint of the air filter should not be lower than 163°C.

      2.1.8 The medium-efficiency air filter should not be used independently, but should be used in combination with the pre filter.


  2.2 The key to construction and installation

      The air filter should not be installed directly on the downwind side of the shower room or humidifier. Effective measures should be taken when it is really impossible to avoid it.

  2.3 Related standard

      07K505 "Design and Installation of Clean Operation Department and Medical Gas".


  2.4 Implementation standards

      Product standard: GB/T14295-93 “Air Filter"; JG/T22-1999 "General Ventilation Air Filter Performance Test Method"

  Engineering standards: GB50073-2001 "Clean Workshop Design Standard"; GB50333-2002 "Hospital Clean Operating Department Building Technical Standard".


3. HEPA

  3.1 Introduction of HEPA filter


      3.1.1 The main parameters selected for HEPA filters are filtration efficiency, rated air volume, initial resistance under rated air volume, dust holding capacity, etc.

      3.1.2 According to the method specified in GB/T6165-1985 "HEPA filter performance test method Transmittance and resistance", the transmittance is ≤0.1% (that is, the efficiency is ≥99.9%) or for particles with a particle size of ≥0.1μm, the filter with the counting transmission rate ≤ 0.001% (ie, the filtration efficiency ≥ 99.999%) is a HEPA filter.

      3.1.3 The commonly used filter materials for high-efficiency air filters are ultra-fine glass fibers.

      3.1.4 The air filter should meet the fire protection requirements. The high-efficiency air filter is divided into three levels according to the degree of fire resistance: level 1 filter, all materials of the filter are non-combustible, and non-combustible materials should comply with GB8624-1997 Class A; for level 2 filters, the filter material should be a non-flammable material that meets GB8624-1997 Class A, and the partition and frame can be made of a flammable material that meets GB8624-1997 Class B2; the 3-level filter, all materials of the filter are available in accordance with GB8624-1997 level B3.

      3.1.5 When designing, the resistance of the filter can be calculated by twice the initial resistance as the final resistance.

      3.1.6 The initial resistance of the HEPA shall not exceed 10% of the resistance of the product sample.

      3.1.7 The high efficiency air filter should not be used alone, and the HEPA should be installed at the end of the purification air conditioning system.

      3.1.8 The supplier shall provide the dust holding capacity. ZhongJian South’s  high-efficiency filters should be leak-tested when they leave the factory. Other requirements are determined according to user needs.

      3.1.9 In general non-parallel flow clean air conditioning systems, combined filter vents are often used.

Second, the key of construction and installation

  3.2 The key to construction and installation

      Attention should be paid to the installation and sealing of HEPA. The sealing methods include contact packing sealing, liquid groove knife-edge sealing and negative pressure leakage sealing.

  3.3 Related standards

      07K505 "Clean Operation Department and Medical Gas Design and Installation"

  3.4 The implementation of standards

   Product standard: GB13554-92 "High efficiency air filter"; GB/T6165-1985 "High efficiency air filter performance test method-Transmittance and resistance"

  Engineering standards: GB50073-2001 "Clean Workshop Design standard"; GB50333-2002 "Hospital Clean Operating Department Building Technical Standard

Table of filtration efficiency and resistance of HEPA

   Classification Filtration efficiency under rated air volume (%) Filtration efficiency under 20% rated air volume (%) Initial resistance under rated air volume (Pa) Remarks

Class A particle size ≥0.5μm, ≥99.9 — ≤190 Class A, B, and C efficiency are sodium flame method efficiency; Class D efficiency is counting efficiency;

Class B particle size ≥0.5μm, ≥99.99 ≥99.99 ≤220;

Class C particle size ≥0.5μm, ≥99.999 ≥99.99 ≤250;

Class D particle size ≥0.1μm, ≥99.999 particle size ≥0.1μm, ≥99.999 ≤280;






2021-12-29 154People browsing Back

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