Definition
Cold-chain logistics keeps temperature-controlled goods, such as food, medicines, and fresh products, inside a specified range through production, storage, transport, and delivery. Temperature and humidity sensors, temperature sensors, and GPS provide monitoring and a record that can be traced, so quality and safety can be checked. The chain has to meet HACCP, GSP, and FDA rules, and it works with bonded warehouses, overseas warehouses, and last-mile delivery.
The main stages
The chain covers cold storage (the refrigerated area of a bonded warehouse or an overseas warehouse), refrigerated transport (reefers and refrigerated containers), and final delivery (insulated packs and immediate delivery on the last mile). The band depends on the product: frozen at −18°C or below, chilled at 0°C to 4°C, and cool at 15°C to 25°C. Temperature and humidity sensors and temperature sensors read continuously and alarm when a limit is crossed.
IoT in cold-chain logistics
IoT makes the chain visible and traceable. Temperature and humidity sensors and temperature sensors send readings over 4G, WiFi, or Bluetooth to the cloud platform. GPS tracks the route. Blockchain can make the record harder to alter unnoticed. The data supports compliance audits, HACCP and GSP certification, and assigning responsibility in reverse logistics. SimtoLink can connect sensors, track the route, and integrate through APIs.
Implementation Guidance
Putting a cold chain in place means installing temperature and humidity and temperature sensors, connecting them to the cloud platform, writing the temperature procedure and the response to an excursion, and meeting HACCP, GSP, and FDA. With electronic customs declaration, multimodal transport, and last-mile delivery, temperature can be followed across a cross-border chain.
Temperature band, probe location, and breaks in the chain
A cold chain has to record the time goods spend inside a required temperature band, and whether that time was measured without a break. Frozen, chilled, and cool each have an upper and a lower limit. The limits come from the stability requirement of the goods, not from the setpoint on the vehicle panel. The record must be matchable to a specific case or pallet, a vehicle, and a handover time. A probe measures the air or medium around it. Placed at the return air, at the door, or in the core of the load, it draws a different curve. Only read together with how the load was stacked does it come close to the goods temperature.
Before use, packaging and precooling should already have brought the goods into the target band, and refrigeration capacity should cover door openings, sun, and the actual load. Both sides of a handover should record, on the same time base, when monitoring stopped and when it was connected again. Across carriers, each segment of the record must join the next. Sorting on a dock with nobody monitoring leaves a gap that cannot be explained. Drugs and food differ in shelf life, calibration, and what to do after a limit is crossed. A single-use recorder on a food case cannot be used directly as the basis for releasing a drug. On a short run that uses passive cooling, record the coolant type and its starting state at packing, not only the air temperature at departure.
Treating the setpoint as the goods temperature is a common error. The cabin display can sit in the chilled range while the stack by the door is warmer. A recorder at the return air can draw a tidy curve while the core of the load has already drifted. Turning the recorder off at handover and on again for the next leg leaves several hours with no data, then joins the two curves into one continuous line afterward. An alarm that reaches only the driver's personal phone, with no disposition record on the company side, cannot show an auditor whether the goods were isolated or stopped. A probe past its calibration date can keep uploading. The numbers look complete, and the bias is unknown.
Filing by vehicle rather than by shipment also fails. When one vehicle mixes different temperature bands, one cabin curve cannot prove every shipment was compliant. Pull one complete waybill and check that precooling, loading, transit, and unloading all have overlapping records, and that someone confirmed each point over the limit. If probe location, calibration date, or shipment number is missing, that curve cannot stand alone as a release basis. Records tied to GSP or HACCP must also be exportable by shipment, not by vehicle.
Check door openings as well. How long the door was open, how many times, and whether the stack then left the probe's coverage, should all be written on the same shipment. Keeping only the cabin average will average away the short rise caused by loading and unloading. The curve can look compliant for the whole trip while the core temperature has already left the target band.
Goods that were not precooled enough should have their starting deviation written separately, even if the in-transit curve looks compliant. Do not use the average temperature while the vehicle is moving to hide the time, before loading, when the goods were already outside the band.