Often seen these ,but what are they for ?when would you use it ?
They’re for chilled loads of veg that need a bit of fresh air to reduce sweating/condensation.
Ah thought it was something like that,probably the reason nearly all Spanish fridge operators have them.
and it also lets some air in for the illegals.
Deeireland:
‘… Small flap door in the door of a fridge door … what are they for?..’
The maximum repeat of one word in a thread title 
Its called a probe appature.If a vehicle arrives at a cold store they open the flap and put in a temperature probe to check the box temperature before accepting delivery.If they opened the barn doors the “cold” would drop out the box and give a false reading as ambient air would flow in from the top of the door.
Also used for the drivers sandwiches 
truckyboy:
Also used for the drivers sandwiches
…or any freebies that need chilling 
On P&O Ferrymasters I used to tip soap powder and reload cheese regular, they wouldn’t load the cheese until the smell of soap was totally gone so I used them to air the fridge out on way to collect cheese . They had one on front and one on back doors . Worked a treat
newmercman:
They’re for chilled loads of veg that need a bit of fresh air to reduce sweating/condensation.
They’re obviously tried and tested for that purpose,but why doesn’t all the dirt that always coats the rear doors get sucked in and contaminate the load?
Happy Keith:
Deeireland:
‘… Small flap door in the door of a fridge door … what are they for?..’The maximum repeat of one word in a thread title
Nice constructive post as ever there Keith, well done.
newmercman:
They’re for chilled loads of veg that need a bit of fresh air to reduce sweating/condensation.
that’s what the defrost system does … other wise every trailer that’s a chiller would have one in…
I was always told how ever it was for venting the trailer after carrying a load that left a taint in it ie Fish … open vent bang fridge on constant and let it vent whilst driving to next collection … we use to spread a cheap coffee on the floor and sweep out before collecting
Good luck trying to get fish odour out of a trailer by opening a little door 
I reckon they are for ventilation ,I’m sure someone will know exactly.
A tempeture probe maybe ,it must be a big probe would a small rubber sealed hole not be easier.maybe they are for if some git locks you in you can stick your arm out and open the door.
Remember the dutch driver found with a load of dead chinese in it hadnt he shut them vents up and suffocated them.
kr79:
Remember the dutch driver found with a load of dead chinese in it hadnt he shut them vents up and suffocated them.
He had already got his money, if he hadn’t got stopped in Dover he would have continued up to Morecambe Bay to tip them on the beach. 
newmercman:
Good luck trying to get fish odour out of a trailer by opening a little door
Do I detect a hint of cynicism there Mr Lee? (know that stench well after moving pallets for Tradimar recently)
As for using the flap for a temperature probe, isn’t it more pertinent to take the temperature of the goods rather than the box temp?
~ Craig
Over here in North America, a lot of dry vans have them too. Probably just for ventilation as Newmercman says. When I used to carry seed potatoes down to Florida during the winter months, when we got to the Carolina’s and the temp got to a certain warmth we where instructed to open the flap because of the humidity.
Never had any dirt get sucked in to the back and contaminate the load though. Seed potatoes wouldn’t matter any way, they’re going straight back in to the ground and they often unload them with a bobcat, cleanliness isn’t a priority.
Craig 111:
newmercman:
Good luck trying to get fish odour out of a trailer by opening a little doorDo I detect a hint of cynicism there Mr Lee?
As for using the flap for a temperature probe, isn’t it more pertinent to take the temperature of the goods rather than the box temp?
~ Craig
Cynical? Moi?
Ventilation ■■? The fridge ■■■■■ in fresh air through the condensor then blows it through the evap unit to cool it.Then it ■■■■■ it out the front bulkhead vents.How much ventilaton do you want?
Thats why they tell you not to load above the red line so cold air can circulate.