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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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