Failed a bay appointment at a major supermarket DC about eighteen months ago. Not the fridge unit — that was fine, Carrier unit on a Montracon tri-axle, never gave me trouble. Not the load — sealed, palletised, collected in good condition from a cold store outside Bristol. The problem was the temperature probe log, which showed a two-degree excursion during a two-hour crawl on the M5 near Cheltenham. The bay rejected the load. Three hours of waiting for re-inspection. An earful from the planner.
I hadn't done anything wrong. But the log told a story and the supermarket's quality team weren't prepared to wave it through on the basis of my explanation. That's temperature-controlled work. The paperwork matters as much as the actual condition of the goods.
If you're moving into fridge work — or if you've been doing it for years without thinking too hard about the compliance side — this is what the job actually requires beyond knowing how to set the thermostat.
What the ATP certificate covers
ATP stands for Accord relatif aux Transports Internationaux de denrées Périssables — the international agreement on the carriage of perishable foodstuffs. Despite the French name, it applies to UK domestic work too, and it's the standard most food retailers and distributors require regardless of whether your load is crossing a border.
The ATP certificate is issued to the refrigerated unit (the trailer or body) and confirms that it can maintain the required temperature range. A unit certified for frozen work (typically -20°C or colder) is different from one certified for chilled work (typically around 0-6°C, depending on the goods). You can't use a chilled-only unit for frozen work and expect it to pass an ATP inspection — the insulation and the refrigeration capacity are different specifications.
Certificates are issued by DVSA-approved inspection stations in the UK. The validity period depends on the age and type of the unit — check the certificate itself for the expiry date. When it expires, the unit needs re-testing to maintain the certification. Keep the certificate in the cab. Not in the office. In the cab.
Most retail customers — particularly the major supermarket chains and food service companies — will check ATP certification at the point of booking. If your unit isn't ATP-certified for the temperature class they need, you won't get the work. For smaller operators moving into refrigerated distribution, ATP certification of the trailer is an entry requirement, not something you sort later.
What temperature the goods actually need
There isn't one temperature for "cold" work. The goods dictate the requirement.
Fresh produce — salad, mushrooms, some baked goods — might need 8°C or above (chilled, not cold enough to damage the product). Dairy typically runs at 4-6°C. Chilled ready meals: often 0-4°C. Frozen goods: -18°C or below is the standard requirement under UK food safety regulations. Some frozen goods — particularly ice cream — need -20°C or colder throughout transit.
The carrier (the refrigeration unit) needs to be set for the goods, not for what the last driver had it at. Taking over a trailer that was running at 4°C for fresh produce and loading frozen goods without pre-cooling to -18°C first is a problem that'll show up in the temperature log at the delivery bay. Allow pre-cooling time before you load. It's in the job — budget for it.
Multi-temperature trailers exist. They have a bulkhead divider that separates a frozen section from a chilled section. Each zone has its own thermostat. Managing the zones correctly — particularly making sure the bulkhead seal is intact and that the fresh section isn't being pulled below temperature by the frozen section — is something to check at loading, not at the bay.
The temperature log and why it matters more than you think
Most refrigerated trailers have continuous temperature logging — a probe in the cargo space recording temperature at regular intervals throughout the journey. The log prints or uploads at the delivery point. Some retailers download it directly from a port on the unit without asking you.
The log tells a story about what happened to the load from the moment it was loaded to the moment it arrived. If there was a door opening in transit — say, during a multi-drop where you opened the rear for one delivery — it shows. If the unit struggled during a long idle in traffic on a hot day, it shows. If someone loaded the goods without proper pre-cooling and the temperature was high for the first two hours, it shows.
From the driver's side, the practical implication is: document anything unusual. If you had to wait two hours outside a gate in summer heat with the unit running at maximum, note it. If the goods were warmer than they should have been at loading, note it. A temperature excursion you can explain is better than one that arrives unexplained at the delivery bay.
Some operators use temperature logger printouts as part of their proof of delivery documentation. That means the driver needs to understand how to print or download the log from the unit. If you've never done it — ask the fitter who signs off the vehicle at the yard. Every brand has a slightly different interface. Don't find out you don't know how to do it at the bay gate when the quality team's waiting.
What to do when the fridge unit fails on the road
It happens. Carrier units, Thermo King, Zanotti — they all fail eventually. Usually at the worst possible time, which is always a hot day on the M6 with four hours of driving left and a time-critical load in the back.
First call is the operator. Not the customer — the operator, who can advise on whether to continue (if the goods have sufficient temperature margin), divert to a cold store, or return. The decision about whether the goods are still within specification after a unit failure is the operator's and the customer's call, not yours. Your call is to report it immediately and stop the temperature from going further.
Keep the doors shut. Opening the back to check the goods when the fridge is down accelerates the temperature rise. Leave them sealed unless you're at a cold store with proper facilities.
If you have a breakdown service for the refrigeration unit — most operators with refrigerated fleets do — call them. Unit repair in transit is sometimes possible. If not, the question is whether the goods can make it to the delivery point within safe temperature limits with the unit off. That depends on the goods, the ambient temperature, and the remaining transit time. It's not a decision to make unilaterally.
What happens at the bay if the load's rejected
Rejection is the delivery site's right if the goods don't meet the temperature specification. From the driver's perspective, that means: don't load it back in anger, don't argue with the bay staff about the temperature logs, and get your operator on the phone before you do anything else.
Rejected loads go back to whoever owns them — which might be the operator or might be the customer, depending on the contract. The driver is usually not the person who decides what happens next. What the driver does need to do is complete proper paperwork: note the reason for rejection, get a signature from the bay staff if they'll give one, photograph the temperature log readout and any documentation they've issued. That evidence matters for the operator's claim against the customer or carrier, if it comes to that.
The liability question — whose fault is a temperature excursion — depends on where the chain broke down. If the goods were loaded warm, that's the shipper's problem. If the unit failed, that's the operator's. If the driver opened the doors at a motorway services and left them open while he had a sandwich, that's the driver's. Temperature logs are quite good at showing which of these happened.
The pre-drive fridge check
Before you pull out of the yard:
- ATP certificate — check it's valid and in the cab
- Unit temperature setpoint — correct for the goods you're carrying
- Pre-cooling — has the cargo area been pre-cooled to the target temperature before loading?
- Fuel for the unit — most trailer units run on diesel from a separate tank, not the tractor. Check it
- Door seals — any visible damage to the trailer door seals lets warm air in and cold air out
- Temperature probe — is the logging system powered and recording?
Takes three minutes. Saves the kind of afternoon I had on the M5.
Tracking your hours on refrigerated routes is the same 561/WTD framework as any other HGV work. ShiftOwt handles the compliance side — from £5.99/month for drivers, which adds up to less than a rejected load investigation does.