What the Regulations say about Redundant Sensors in GxP Environments
Do I need separate instruments for monitoring and controlling critical parameters in a WFI system.
If YES where can I find that in FDA CFR or Eudralex?
If NO where can I find that in FDA CFR or Eudralex?
Vaisala Life Science Industry Expert Piritta Maunu wrote in reply:
This is an excellent question and you are not alone in having asked.
In practice, Eudralex EU GMP Volume 4 or FDA Code of Federal Regulations Title 21 regulations rarely give exact rules for questions relating to parameters or specific technologies. So the short answer is – no, you probably won’t find a specific regulation regarding adding separate, autonomous instruments.
However, if we can’t find clear guidance in the regulations, we should evaluate the issue based on the risk management principles that both EU GMP and cGMP strongly advocate. In the case of instrumentation for a WFI (water for injection) system, we can conclude that this is a critical system because it’s key to a process that will be focused on during an inspection.
There are two other criteria that help define us this system as critical:
• Issues with this system might impact patient safety.
• Issues with this system could harm your company’s reputation, or cause extra work if the system is cited as problematic during an inspection.
In both scenarios, the risk is unacceptably high.
So best practice is to evaluate the risks related to system malfunction according to risk management principles.
Probability x Severity of Impact = Level of Risk
And the more risk inherent to a system, the more attention we pay to the system in terms of preventive maintenance, planning, validation and documentation.
This leads us to risk mitigation actions for any systems we evaluate as critical.
One fairly simple solution to mitigate risks like this is to add redundant sensors. Two separate sensors rarely fail or drift exactly the same way at the same time. Specific to WFI systems,one approach to is use a separate controlling and monitoring sensor. This simple redundant sensor approach gives us ability to compare sensor results and to react earlier to possible problems.
However, in my opinion this is why we often get different answers (yes and no) to this type of question. Some companies mitigate risks by using redundant sensors. Some companies mitigate risks with other solutions like following other internal procedures such as daily or weekly equipment/sensor checking activities.
Whatever you do, your decisions should be based on the principles of risk assessment.
Interestingly, I had the same discussion in R3 Nordic Symposium and Exhibition, in Naatali, Finland in May 2018. In that conference several different cleanroom area manufacturers and validation experts agreed that it's a current good practice in cleanrooms and with critical equipment (like sterilizers, autoclaves, depyrogenation equipment, etc.) to use redundant sensors. You can also use handhelds for scheduled spot checking sensors that are integrated to equipment, or a secondary fixed sensor that is calibrated regularly; that will serve as your redundant sensor and ensure that any associated problem is immediately identified before quality is at risk.
While there is no regulatory guidance recommending redundant sensors, this is a common practice derived of quality risk management principles for critical processes and equipment. From our industry contacts we’ve seen that the practice is becoming more common in many GxP-regulated applications.
I hope you find this answer useful. Please find some links below to more training materials on Risk Assessment for GxP environmental management. A useful document is the ISPE’s GAMP 5 “A Risk-based Approach to Compliant GxP Computerized Systems.”
Vaisala Industrial Measurements, Products and Systems (R&D and technology development)
More Information on Performing Risk Assessments:
Calibration Risk Assessment
ISO/IEC 17025:2017: New definitions for specifications, decision rules, & risk assessments for calibrations
Calibration Risk Assessment: Where to Start (includes Vaisala's Calibration Guide)
More reading on GxP Environmental Management Best Practices:
- Using the ISPE’s GAMP Methodology to Validate Environmental Monitoring System Software
- Metrology in Life Science Environments
- 10 Articles on Quality, Metrology, and cGMP/FDA Regulations