Know how


Clean room classes:

Clean rooms offer working conditions and air conditioning on especially high purity standard. Clean rooms are used in particularly in the chemical industry, pharmaceutical industry, semiconductor electronic industry and many special industries.  

Different standards/norms were developed from this application fields.
The table shows and compares different actual international classification.


  • Comparison of international standards:

    The table shows a comparison of different international classification standards.

    In the pharmaceutical industry and for medical facilities the rooms are mostly classed to GMP.  Attached table shows a comparison to the ISO to clean room classes.

    Filter stages to reach the correct clean room class:

    To reach the aimed clean room class, diverse filter stages are necessary. It is also of big importance, where to situate the filter stages. (air ventilation unit, cannel system, room inlet…)

    The attached overview is an important guideline for the planner.
    It shows applicable filter combinations in order to reach the accordant clean room class.  

    1st and 2nd filter stage:

    This is the prefiltering before the HEPA (3rd filter stage)/ULPA (4th filter stage) filter. The mostly used filtertype is the pocket filter.
    The quality of the prefiltering has big influence on the dust loading and life time of the following filter stages. We recommend pocket filters of product line "durotex" in high flow execution.

    To gain long life time and best Energy-efficiency  it is necessary to use an excellent pre-filter. Such as pocket filters product line filtex®durotex, filtex®durotec oder filtex®glass. For teh final pre-filter stage we recommend compact filters  filtex®ripac . In case of increased process risk or if there are extremely high air flow rates,  for the 2nd filter stage a rigid filter, product line “ripac” should be used instead of pocket filters.

  • 3rd and 4th filter layer:

    Mostly the 3rd filter stage is a HEPA filters of class E10 to H1. (=HEPA filter = High Efficiency Particulate Air filter)
    The 4th filter stage is an ULPA filter (=Ultra Low Penetration Air filter) of class U15 to U17.

    HEPA an ULPA filters have a consistently high filtration efficiency from the beginning to the end of life time. The final pressure drop reaches up to 600 Pa.

    By use of high-quality filtex® filters, the pressure drop and resultant the energy waste can be lowered significantly. The additional effect is a rise in the filter absorbance quality and higher process reliability.



    To minimise the process risk, filters and frames can be supplied with option "sealing-test-prove".
    So, after every filter change,  the correct fitting up of the filter into the frame can be tested.

    Filtertest and Reporting System:

    The EN1822 standard must show average and local efficiency a stated air flow rate. It mus also show initial pressure drop and reached filter class.

    filtex® EPA/HEPA/ULPA filters are subject to highest quality control standards. Single test for each filter.

    Clean Room - validations:

    Clean rooms are subject to strict safety regulations in order to minimise the process risk. In particular for pharmaceutical industry, food industry, medical technology, research, semiconductor technology, coatings...

    To guarantee the clean room class, the rooms must be validated by external specialists periodically.