As normative fundament for the monitoring of cleanroom systems the Draft International Standard ISO/DIS 14644-2.2 “Monitoring to provide evidence of cleanroom performance to air cleanliness by particle concentration” published in September 2014 is recommended above all, as it reflects the present state-of the-art comprehensively. In addition, the German guideline VDI 2083 Part 3.1 “Cleanroom technology – Metrology in cleanroom air – Monitoring” (www.beuth.de) is also appropriate for being used for this purpose. Only parameters which are of general relevance in the context of pharma monitoring of HVAC systems will be discussed below. There are two types of data to be distinguished (see Figure 1). It makes sense to incorporate into the pharma monitoring system also the functional control of air lock doors and their alarms.
Figure 1: Data types for pharma monitoring
In order to ensure early warning against any problems developing during the operation of the HVAC systems, other utilities and the processing equipment, alert and action limits (see Figure 2) should be determined for the key physical parameters requiring monitoring. By means of a two-step approach to developing excursions of monitoring data, alerting thus also provides a sound and objective input for trend analyses of process and cleanroom performance.
Figure 2: Two-step approach alterting to excursions of monitoring data
How to establish alert and action limits? Taking the pressure difference between rooms as example, the limits shown in Figure 3 will assure that even in the worst case no flow reversal will occur at the action limit: there is still a pressure difference of 3 Pa available for ensuring that. If the 30 Pa Δp value falls to its lower action limit, i.e. to 24 Pa and the 15 Pa Δp value rises to its upper action limit, i.e. to 21 Pa, there is still a pressure difference of 3 Pa available for assuring that.
Figure 3: Proposal for alarm and action limits for pressure differentials
Alarms due to exceeding the alarm and action limits of control parameters should be transmitted to the computerized pharma monitoring system and registered there inextinguishably. Alarms should be triggered individually when alert or action limits are exceeded and should be recorded indelibly in electronic form.
In addition to these alarms alerting to serious excursions of control parameters also alarms triggered by incidents like airlock doors being kept open for too long should be incorporated into the automatic alarm module of the pharma monitoring system.
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Monitoring of HVAC Systems in GMP Environments
Dr. Hans H. Schicht