Environmental Monitoring - II
The ventilation systems used to supply air to clean rooms have already been referred to. We shall now look at the physical monitoring that is carried out on these systems. Particulate matter counts are carried out with a particle counter that measures the number of particles in a given quantity of air. They should be carried out during validation and at regular intervals thereafter. You can consult ISO 14644 for more details on the methods and locations for monitoring particles.
The differential pressures between rooms are measured by means of manometers. The manometers should be calibrated and should provide continuous monitoring. Values should be recorded regularly.
The number of air changes within a room is calculated from the air volumes supplied to the room. The calculation should be made during validation and regularly thereafter.
The HEPA filter integrity is tested by a number of means. An aerosol generator can be used to send an aerosol across the filter and a photometer used to view it. This will show whether there is any damage to the filter. Additionally, a manometer can be used to measure the pressure differential across the filter. These tests should be carried out when filters are installed and repeated at regular intervals (at least annually). Again, you should verify compliance with this by reviewing the SOP and records to assess compliance with the SOP.
The temperature and humidity can be measured by a variety of instruments from the very simple to the very complex.
Several of the above parameters can be monitored automatically, and new factories often have sophisticated building management systems (BMS) that not only monitor, but also make adjustments if required. If you are inspecting a factory with such a system, it is worth spending some time checking on the understanding of the personnel regarding this system. It can be all too easy to assume that everything is under control and not notice when something goes wrong. Establish whether any validation had been done to ensure that all the controls and monitors are working as intended?