Selecting Data Loggers for Validation Applications

Under AS/NZS 5369:2023, the measurement equipment used during validation needs to support the requirements of the applicable process standard. For steam sterilization this includes ISO 17665, while washer-disinfector validation is supported by the ISO 15883 series.

The appropriate measurement system therefore depends on what needs to be measured, where it needs to be measured and the process conditions under which the measurement is made.

Data logging systems used for steam sterilization should therefore be selected with consideration of:

• suitability for saturated steam, sterilization temperature and pressure
• sensor dimensions and thermal mass
• ability to position the sensor at the required measurement location
• temperature accuracy and response time
• sampling interval
• relevant pressure measurement where required
• appropriate calibration and verification.

Washer-disinfector validation presents a different measurement environment.

The ISO 15883 series requires assessment of defined process conditions during cleaning and thermal disinfection. Unlike steam sterilizer PQ, measurements may therefore be important across several stages of a changing process:

pre-rinse → cleaning → rinsing → thermal disinfection → final rinse → drying

This means the logger needs to perform reliably across the relevant temperature range, including the lower temperatures associated with cleaning as well as the higher temperatures used for thermal disinfection.

Instrumentation also needs to withstand exposure to:

• water and direct spray action
• detergents and process chemistry
• repeated heating and cooling
• thermal disinfection conditions
• mechanical movement within the load.

A current calibration certificate is important, but calibration alone does not demonstrate that a logger is suitable for a particular validation test.

The calibration should be relevant to the temperature range over which the measurements will be relied upon, with appropriate consideration of:

• calibration points and range
• measurement accuracy and uncertainty
• sensor identification
• reference traceability
• verification required by the applicable test standard.

Both wired systems and self-contained wireless loggers can provide valid measurement evidence. Neither is inherently suitable for every application and in some instances, both may be required.  Eg:  to conduct Chamber Wall Temperature Tests, attaching sensors to a chamber wall of a washer-disinfector may not able to be achieved using wireless loggers, therefore compliant testing of a washer-disinfector would require both wired and wireless loggers.

Wireless loggers can simplify placement throughout equipment chambers and loads, but their physical dimensions and thermal mass may limit their suitability where measurements are required within small or complex RMDs.

Wired or remote-probe systems can allow much smaller sensors to be positioned within restricted locations, although cable routing and installation introduce different considerations.

Selection should therefore follow the measurement requirement, rather than a preference for a particular logger technology.

Selecting the logger for the test – before selecting data logging equipment, consider:

1. Is the logger compliant with the test equipment specifications of the respective Standard?
2. What must be measured?
3. Where must it be measured?
4. Can the sensor reach that location without influencing the process?
5. Is its accuracy and response appropriate for the acceptance criteria?
6. Is its calibration relevant to the temperatures being assessed?
7. Can it withstand the process environment?
8. Does it satisfy the applicable validation test requirements?
9. Can the resulting measurement be clearly traced to the logger, calibration record, test location and PQ result?

SVA understands that reliable validation depends on more than selecting and positioning data loggers. The instrumentation itself must be fit for purpose, with appropriate specifications, accuracy, resolution, calibration and traceability for the process and conditions being assessed.

Drawing on specialist validation knowledge and practical experience, SVA selects and applies instrumentation appropriate to each application, including the required operating range, response characteristics, sampling requirements, sensor placement and acceptance criteria. This ensures the resulting data provides reliable and technically relevant evidence of process performance.