A thermal bag is for short routes measured in hours: light, suited to a motorcycle courier, but with lower thermal performance than a rigid box. If the route is long or waiting is likely, a rigid box and a higher-capacity cold source are needed. Because closure, seams and handling change the result, a catalogue's insulation thickness cannot predict a safe duration.
- Closure and zip: must shut firmly; an open lid wastes the insulation.
- Lining: wipeable, with seams that do not trap dirt; in a fabric bag the cleaning instruction matters more than with a rigid box.
- Divider: the product never touches the coolant pack directly.
- Logger: the sensor sits beside the product, away from the pack.
The EU GDP Guidelines tie container selection to the product's storage conditions, the expected external temperature extremes, the longest transport time and the qualification status of the packaging (Article 9.3), and ask for temperature mapping that covers seasonal variation for temperature-sensitive products (Article 9.4). For a bag, that means repeat trials with a representative load. Do not rely on start and end readings; review the temperature profile along the journey and the extremes near the product.
Record results against the bag ID and loading method, and repeat the test after cleaning or wear. If the trial does not hold the condition all the way, the route, packout or container changes.