Particulate Filtration

The advances in technology are placing ever-increasing requirements on the need for creating and maintaining gas purity in glove boxes. Particle count and particulate removal feature increasingly in the requirements for environmental health and safety, process protection and equipment performance.


Environmental protection from the release of harmful particulates when accessing or venting a glove box, process protection from the particles that may be released from the gas purifier into the glove box, and gas purifier protection from the process materials in the glove box. All require consideration and selection of particulate filters to suit the needs of the protection.


The designer has commercially available filters in the HEPA or ULPA range, with popular filters rated 99.99% efficient at removing particles down to 0.3 micron in the former and 99.999% efficient at removing particles down to 0.12 micron in the latter.


However, filters need to be selected which are compatible with their environment, as incorrectly selected they can be affected by and/or have an affect on the process conditions. Additionally, filters have to operate for extended periods (often in critical applications) and it is important to understand how they will perform.


European Standards adopted for assessing and classifying the performance of filters provide an excellent basis upon which quality can be assured.


New EN Filter Classification Chart


EN 779 Class
Method for assessing and classifying the performance of particulate filters.
G1 Am < 65
G2 65 = Am < 80
G3 80 Am < 90
G4 90 Am
F5 40 Em < 60
F6 60 Em < 80
F7 80 Em < 90
F8 90 Em < 95
F9 95 Em
   
Am = Average arrestance for Course Filters in the classification range G1-G4
Em = Average efficiency for Fine Filters in the classification range F5-F9

EN 1822 Class
Performance assessment of HEPA and ULPA filters.
 
E % @ 0.3 µm   E % @ MPPS
95 H10 85
98 H11 95
99.99 H12 99.5
99.997 H13 99.95
99.999 H14 99.995
     
E % @ 0.12µm   E % @ MPPS
99.9995 U15 99.995
99.99995 U16 99.99995
99.999995 U17 99.999995
     
E % = Mean fractional efficiency for HEPA & ULPA filters in the classification range H10 - U17.
MPPS = Most penetrating particle size.

 

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