A reefer Pre-Trip Inspection, PTI, is a mechanical pass or fail on an empty refrigerated container before it goes anywhere near your cargo. It tells you the unit can reach and hold its set point, defrost correctly and circulate air, on the day it was tested, in an empty box. It does not tell you anything about the box three weeks later, mid-ocean, with a full load inside it. Shippers of perishable or temperature-sensitive freight who treat a PTI decal as a guarantee, or who load a warm container because the PTI passed, are the two most common ways this goes wrong.
This guide covers what a PTI actually tests, the numbered test tiers you will see on some containers and why they are not a single industry-wide scale, who is meant to request and pay for it, pre-cooling before stuffing, what temperature-recording rules actually apply to certain perishables under U.S. law, the three broad types of reefer data logger and what a claim needs from one, ventilation settings for cargo that respires, and where PTI stops and ongoing in-transit monitoring starts.
What a Reefer PTI Actually Tests
A full functional PTI runs on the empty unit before it is released for loading, in roughly three phases. First, a power-off visual inspection: door seals, drain lines, interior cleanliness and structural condition. Second, a power-on functional phase, typically three to four hours: the controller runs its own automated self-test of components, and a manual check covers the refrigeration and ventilation hardware, the compressor, the fans, the sensors and the alarms, ending with a functional pull-down run to the required set point that includes a defrost cycle and a check that the temperature recording device is logging correctly. Third, documentation: the result is recorded pass or fail, with a physical decal and a digital record in the carrier's system.
The self-test a controller runs at component level is manufacturer-specific. A published breakdown of one common controller's automated pre-trip codes shows the shape of it: heater activation and deactivation, condenser fan start and stop, low- and high-speed evaporator fan checks, a comparison of supply and return temperature probes during an eight-minute high-speed fan run, compressor and valve tests, a high-pressure switch check, a perishable-mode pull-down and hold test, and finally defrost and frozen-mode checks. That is what "PTI tests the set point, the defrost cycle, airflow and the data logger" looks like once you break it down.
Is There a Universal "PTI 1 Through PTI 7" Scale? Not Quite
You will see numbered PTI designations in the trade, and it is worth being precise about what they mean, because they are not a single graded certification scale that every carrier and depot uses the same way. What is verifiable is that Carrier Transicold, a reefer machinery manufacturer, defines automated test tiers on its controllers: a short "Auto PTI 1" of roughly 20 minutes for basic functional checks, a long "Auto PTI 2" of more than three hours that adds a full temperature pull-down test, and a newer "Auto PTI 3" of about two hours that runs the same sequence as Auto PTI 2 but stops before the frozen-cargo tests, intended for perishable cargo that cannot tolerate an extended cooling interruption on the test bench. Depot and container-service operators separately describe their own commercial tiers, such as a quick "short" test for chilled goods and a "full" test with extended temperature simulation, and some carriers have started layering in condition-based "smart" tests that skip a full physical teardown for units with a clean, recently monitored history.
None of that adds up to one "PTI 1 to PTI 7" scale that means the same thing at every terminal. If a carrier, depot or booking form quotes you a numbered PTI level, ask what that specific number covers rather than assuming it maps to a scheme you have seen elsewhere. Two different operators using "PTI 2" can mean two different test depths.
Who Requests PTI, and Who Pays for It
The container and its refrigeration unit belong to the carrier, and a standard PTI before an empty reefer is released for loading is bundled into normal equipment handling, so the cost of the routine test sits with the carrier as equipment owner rather than being itemised back to the shipper. What the shipper, or the forwarder booking on their behalf, is responsible for is telling the carrier what to test against. Maersk's own reefer booking documentation for export shipments asks the booking party to specify the required carrying temperature, the ventilation rate in cubic metres per hour if needed, humidity control, and the voltage, ampere and frequency details, so the depot tests the unit to the cargo's actual requirements rather than a default, and notes the PTI process itself is estimated to take around six working hours once the request is in.
Lead time varies by carrier and terminal and can be tighter than shippers expect. Maersk's published booking guidance for its reefer export corridor through Busan, South Korea, requires the PTI request, with exact temperature, humidity and ventilation figures, submitted at least 48 hours before container pickup, with no exceptions once inside that window, and separately exempts non-operating reefers moved dry from needing a PTI at all. Treat that as an example of how tight this can run rather than a universal rule, and confirm your own carrier's and terminal's lead time before booking.
Whether a shipper can request, and pay for, a more thorough test than the carrier's standard PTI depends on the operator. Carriers commonly offer an extended or repeat test on request, sometimes under a name like the "Auto PTI 2" long test described above, for cargo where the shipper wants documented assurance beyond a routine pass or fail. Whether that carries an extra fee is carrier and depot specific: we could not verify a fixed industry rate for it, so ask directly if your cargo is valuable or sensitive enough to justify one.
Pre-Cooling Before Stuffing: Why a Warm Box Defeats the PTI
A PTI that passes on an empty, ambient-temperature box proves the machinery works. It does not pre-cool the box. Stuffing a container the unit has just proven it can cool, while the box and the air inside it are still at ambient temperature, forces the refrigeration unit to pull down a fully loaded container from a warm start, which takes far longer than cooling empty air and can leave the cargo above its safe range for hours while the unit catches up. That is a separate step from the PTI, and the one most often skipped under loading-schedule pressure.
This is not just operational best practice. For domestic transportation by motor or rail vehicle within the United States, the FDA's Sanitary Transportation of Human and Animal Food rule, in force under 21 CFR Part 1, Subpart O since June 2016, puts pre-cooling into the regulatory chain explicitly. A shipper of food that requires temperature control for safety must specify an operating temperature to the carrier in writing, including the pre-cooling phase if needed, under 21 CFR 1.908(b)(2). A loader must then verify, before loading, that the compartment has been properly pre-cooled as specified, under 21 CFR 1.908(c)(2). A carrier offering equipment with an auxiliary refrigeration unit must pre-cool it as the shipper specified before offering it for loading, under 21 CFR 1.908(e)(3), and records of this have to be kept for 12 months. For the pre-cooling step itself, including how long it typically takes and how to check it before stuffing, see pre-cooling and loading a reefer without breaking the chain.
Temperature-Recording Rules for Certain Perishables
Beyond that general FDA rule, one specific and verifiable U.S. requirement applies to certain imported fruits treated for pest control in transit: USDA's Animal and Plant Health Inspection Service regulates in-transit and in-port cold treatment under 7 CFR 305.6. Where cold treatment is the approved method for a given fruit and origin, the recording devices used must automatically and continuously record temperature, date, time and sensor number through every calibration and the treatment itself, produce a temperature chart an inspector can verify, and be approved and operationally checked by an inspector before use, with sensors calibrated. If calibration or treatment records are found to have been manipulated, APHIS can suspend that vessel or container from further cold treatments until compliant equipment is installed. This is a narrower, higher-bar rule than a routine PTI or an ordinary voyage logger, and it applies specifically to cargo moving under an approved cold-treatment protocol, not to reefer cargo generally. As of this writing the recording-device text has not changed; confirm eligibility and schedule for a specific commodity and origin with APHIS or your customs broker, since these are set separately by species and country.
Reefer Data Loggers and What a Claim Needs
Three broad types of temperature-recording device turn up on reefer shipments. A chart recorder is the older mechanical style, a physical strip that traces temperature over time and has to be retrieved and read by hand. A single-use electronic logger is a small disposable unit placed in the load, stored internally and downloaded once, usually by the receiver or a surveyor, at destination. A reusable Bluetooth or cellular logger sits in the container permanently and, on the cellular versions, can push readings out during the voyage rather than waiting for arrival, which is the technology behind the fleet-wide monitoring programs described below.
Whichever type is used, an insurer or surveyor assessing a temperature claim needs the full logger download for the entire transit, not just an excursion alert, together with the container's PTI record and set point instructions, so a genuine equipment or handling failure can be told apart from a normal, brief defrost-cycle fluctuation that never reached the cargo. Our guide to cold chain data loggers and temperature excursions covers logger placement and reading an excursion report, and our guide to why cargo insurance is worth carrying beyond carrier liability covers what a reefer claim needs once you have that data.
Ventilation: Produce Breathes, Frozen Cargo Does Not
Fresh fruit and vegetables are still alive in the box. They respire, consuming oxygen and giving off carbon dioxide, heat and moisture as they ripen, so produce is typically carried with vents open to a specified airflow rate, exchanging air with the outside to clear carbon dioxide and ripening-related ethylene before it builds up around the cargo. Frozen cargo does the opposite: it is biologically inert, generates no respiration heat, and an open vent simply lets warm, moist outside air into the box, working against the unit and risking ice crystal formation and freezer burn. Getting this backwards, closed vents on produce or open vents on a frozen load, is a real and avoidable cause of damage that has nothing to do with whether the machinery passed its PTI. Our guide to reefer set points, ventilation and humidity covers what to specify by commodity.
PTI Versus Ongoing In-Transit Monitoring
PTI and in-transit monitoring answer different questions. PTI is a one-time, pre-shipment mechanical check on an empty box, confirming the unit can do its job on the day it was tested. In-transit monitoring is what happens after the doors close: a passive logger recorded and read at destination, or an active telemetry feed reporting back during the voyage. Carrier-run examples of the latter are real: as trade press has reported, Hapag-Lloyd began fitting reefer containers with cellular monitoring devices in 2020, installed either at the factory on new containers or during the regular PTI process at depots for existing fleet, targeting roughly 90 percent fleet coverage by August 2023 and the remainder by year end, to flag events such as an incorrect set point or a technical alert while the container is still moving.
A passed PTI and an active monitoring feed are complementary, not interchangeable. A unit can pass its PTI and still develop a fault, a compressor failure or a lost set point, days into a voyage that nothing catches until someone is watching the telemetry or reads the logger at destination. Treat the PTI as the entry ticket and the monitoring as what actually tells you whether the cargo stayed in range.
Before You Book: A Short Checklist
- Specify, in writing, the exact carrying temperature, ventilation rate and humidity your commodity needs, not a generic "keep it cold" instruction, and confirm the carrier's PTI lead time before you book.
- Ask what test the quoted PTI level actually covers if a carrier or depot names a numbered tier; do not assume it matches a scale you have seen elsewhere.
- Confirm the container was pre-cooled to set point before stuffing, not just that it passed its PTI empty.
- Check the type and placement of the data logger before the doors close, and know who is responsible for retrieving and downloading it at destination.
- Set ventilation correctly for what is actually inside the box: open airflow for respiring produce, closed for frozen cargo.
A forwarder who books reefer containers regularly will already have working relationships with depots and know which carriers run a tighter PTI process on your specific trade lane. You can search more than 29,300 logistics companies by country and service in the CargoLinked directory, or browse live freight requests on the public requests board and find forwarders already quoting on reefer lanes.
PTI procedures, numbered test tiers and lead-time requirements vary by carrier, depot and container controller manufacturer, and can change. Confirm the current process, cost and lead time directly with your carrier or depot before booking a reefer shipment, and confirm any USDA or FDA requirement that applies to your specific commodity and origin with the relevant agency or your customs broker.
