How many data loggers do you need for temperature mapping in GxP?

The World Health Organization (WHO) guidelines for temperature mapping suggest placing a data logger every 5–10 meters, with a minimum of 3 loggers in each dimension. For large facilities, this spacing may increase to every 20–30 meters.

The guidelines also state that you need to account for risk zones, such as doors, gates, windows, air outlets, and heat-generating zones, and strategically place data loggers accordingly.

Key factors influencing the number and placement of data loggers mapping

• Facility size and layout: Larger and more complex facilities require more loggers to ensure even coverage.
• Risk zones: Areas prone to temperature fluctuations, such as doors, windows, air outlets, and forklift charging stations, require additional monitoring.
• Storage conditions: The presence of high-density shelving, refrigeration units, or other obstructions can impact airflow and necessitate more data loggers.

With the WHO guidelines, you might end up with a large amount of data loggers needed for your mapping. However, if you apply a risk-based approach, it will often allow you to reduce the number of loggers significantly – typically by around 25% – reducing both the cost and complexity of the mapping process while maintaining compliance and accuracy.

A risk-based approach ensures that data loggers are placed efficiently while still capturing all necessary temperature variations. This is achieved by strategically placing loggers in a less dense pattern while accounting for risk zones. In other words, instead of evenly distributing loggers, they should be positioned strategically based on your risk assessment to monitor the high-risk areas in your operation.

Critical placement locations

• Doors and gates: These areas are prone to fluctuations due to frequent opening and closing. Place additional loggers near entry points to monitor temperature shifts.
• Windows: Direct sunlight and external weather conditions can cause localized temperature variations. Additional sensors may be necessary if windows are not already covered within the sensor grid.
• HVAC and air outlets: Cold air from HVAC systems can create microclimates that affect product stability. Loggers should be placed near vents to track temperature distribution.
• Control sensors: Positioning a logger near the temperature control sensor helps verify the accuracy of the system’s readings.
• Hot and cold generation zones: Areas with equipment that generates heat, such as forklift chargers or zones near refrigeration units, require additional loggers to monitor potential temperature deviations.

Also read: How to choose temperature mapping data loggers and equipment