10 April 1998

Letter box is too expensive

LETTER box ventilation is an impractical and unnecessarily expensive way of applying positive ventilation to pallet box storage, says Scottish engineer Frank Pirie.

Mr Pirie, who makes refrigerated ventilation equipment, developed the suction wall system as an alternative. It costs £47/t in a 1000t store, thanks to a much cheaper £2000 main duct and slatted boxes costing £45/t, compared with £70 boxes used in the letter-box system.

A duct with one vertical slot on each section along one wall of the building is used. Slatted, or even close-boarded boxes are placed on either side and the gap between the rows sealed with a plastic cover. An extractor fan sucks air into the duct.

"It is suitable for ambient, air cooling, air mixing or refrigerated air installations. I suggest the system is well enough proven to merit serious consideration," he says.