Despatch LCC/LCD2-14-3 Non Pass Through Series - Manual (Page 28)

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Validation Testing
Based on the issues discussed in this section, Despatch recommends the following test
sequence for pharmaceutical Class 100 ovens.
1.
Proper installation of the HEPA filters.
2.
Ambient air challenge to determine integrity of oven chamber and filter gaskets.
3.
Proper filter burn-off procedure.
4.
Class 100 testing inside the work chamber.
The Necessity of the Burn-off Process
HEPA filters contain a binder material, which protects the filter media during production
and shipping. This smoke is typically not desirable during normal operation of the oven.
Burning off the binder will ensure a clean process at elevated temperatures.
When the binder is burned off of the filter media, the filter becomes very fragile, too
fragile to withstand normal shipping and handling. For this reason, Despatch does not
perform the burn-off procedure. The burn-off process is not necessary at process
temperatures consistently under 180°C.
Filter Unit Replacement
Replacement of the filter unit is necessary for these reasons:
Resistance, or pressure drop, across the filter unit. Maximum level of resistance
in inches (water gauge) will vary depending upon the operation of the filter and
the available fan capacity. Adequate fan capacity must be available.
Loss of efficiency (leakage), determined from air-sampling measurements made
downstream of the filter unit.
Visible damage or rupture of the filter media in a unit.
Change in process application.
Excessive build-up of lint or combustible particulate matter on the filter unit.
Water droplets in airstream through filter, free water (RH = 100%), will saturate
filter very quickly and may cause burnout or holes in burned off filter media.