You guys may have noticed but, most of the Birds Eye trailers are just insulated reefers with no refrigeration plant fitted.
Birds eye were quite unusual by using a system which maintained the sub zero load temperature using ICI ‘Drycold’ (solid CO2) dry ice blocks laid on top of the pallets. I assume the blocks kept the load frozen for the duration of the journey. I’m sure someone will know!
On the loading dock at Great Yarmouth, you would always see blocks lying on the floor festering after being chucked off the trailer after the journey.
I’m sure no one uses this method nowadays but, Birds Eye obviously thought this was more cost effective and reliable at the time.
Regards.
Stirling.