Cleanroom Pressure Control: Where should the 0 Reference be measured?

The protection concept in pharmaceutical cleanrooms is realised by the different cleanroom classes, zones and their separation by pressure levels. Pressures are assigned to the various cleanliness zones. According to Annex 1, pressure differences of at least 10 pascals are defined between the cleanroom classes. A frequently asked question at this point: Where and how should the reference, i.e. the 0 value, be measured? This refers to the value to which the 0 Pa level is assigned.

It is important that the location of the reference measurement is as well protected as possible from external pressure fluctuations. Pressure surges, e.g. caused by opening doors or wind on the external facade, should not affect the measurement. The pressure measurement probe is usually installed in an empty pipe of DN 250, for example. This can be placed in the technical centre, in the cellar, in the supply shaft or, as already mentioned, in other locations with the greatest possible protection against external pressure influences. An alternative is to mount the pressure sensor on a top-hat rail in the false ceiling area. The -connection remains open. The +connection is connected via a pneumatic hose in the ceiling profile to the measuring nozzle in the cleanroom ceiling.