While average box temperature looks acceptable, product can freeze locally at the point where the gel pack touches it. In vaccine transport, standard cold boxes and carriers rely on conditioned, partly thawed ice packs; an unconditioned pack risks freezing the vaccine, and the conditioning recommended by the World Health Organization is not always followed in the field.
If the product is freeze-sensitive, a thin board, a divider or the product's own carton goes between it and the pack. The separator must not block airflow or lid closure and must hold together when damp; condensation on the pack surface can also collect around the packaging.
