Hauling reefer loads in summer heat

The FDA sanitary transportation rule, in plain terms

This page is general information, not legal advice.

The FDA's Sanitary Transportation of Human and Animal Food rule is in 21 CFR Part 1, Subpart O. It covers shippers, loaders, carriers and receivers that move food by truck or rail in the U.S., whether or not the food crosses state lines. A carrier is whoever physically moves the food (parcel delivery services are left out).

What a carrier must do. These duties apply when the carrier and shipper have a written agreement that makes the carrier responsible, in whole or in part, for sanitary conditions:

The FDA offers a free, one-hour online training module for carriers, with a certificate you can print. It's an easy way to cover the training record.

Who is not covered. Businesses with less than $500,000 (adjusted for inflation) in average annual revenue, averaged over 3 years, are not covered businesses. The rule also leaves out farm transportation, food fully enclosed in a container that doesn't need temperature control for safety, live food animals (except molluscan shellfish), compressed food gases, food contact substances, and food only passing through the U.S. to another country. FDA has also issued waivers for Grade "A" milk haulers under the national milk program, permitted restaurants and retail food stores, and certified shellfish shippers. Even if your revenue is under the line, a broker-carrier agreement can still make these steps part of your contract, so read it.

Pre-cool the trailer the right way

Pre-cooling means running the empty trailer down to temperature before loading, so hot walls and floor don't warm the product. USDA's Handbook 669 says to set the thermostat, close the doors and run the unit until the trailer body stabilizes at the setpoint. In hot summer weather that may take 2 or more hours, so plan it into your arrival time.

The 2019 university revision of that handbook (UF/IFAS) gives this rule of thumb, unless the shipper tells you something else:

• Pre-cool with the doors closed. A trailer with open doors on a hot day just pulls in hot, wet air.
• Shut the unit off while loading at an open dock. Both handbooks warn that running it with doors open can ice the coil and block airflow later in the trip.
• The shipper's written instructions win. Under the FDA rule, the shipper sets the operating temperature, including pre-cooling if needed.

Check product temperature and setpoint before you sign

The UF/IFAS handbook is blunt: transport units are not designed to precool chilled or frozen cargo. Product should already be at or near its carrying temperature when it goes on. If it's warm, your unit can't fix it, and the claim may land on you.

1. Match three numbers: the temperature on the rate con, on the BOL, and the setpoint on the unit. Check °F versus °C on the display. If they don't match, call the broker or shipper before you leave and get the correction in writing. Our rate confirmation guide shows where the temperature terms usually sit.
2. Take pulp temperatures (the temperature inside the product, not the air). The handbook's method: probe one item first so the thermometer settles, then probe a second item about one-third of the way to its center, and wait at least 15 seconds before you read it. Check a few spots: front, middle, back, top.
3. Write it down. If the product is warmer than the shipper's temperature, note the readings on the BOL before you sign, and take photos of the thermometer and the unit display.
4. Set the mode the shipper specifies (next section) and confirm the unit shows the right setpoint before you pull out.

Continuous vs cycle mode, and keeping air moving

Cold air has to travel over, around and under the load and get back to the unit. Block that path and the unit keeps running while parts of the load warm up. From the USDA and UF/IFAS checklists:

• Keep cargo off the air chute (the fabric duct on the ceiling) and below the load line.
• Leave at least 4 inches between the end of the load and the rear doors for return air.
• Keep the front bulkhead clear so air can return freely to the unit.
• Use pallets if the floor channels are less than 2 1/4 inches deep, and keep loads off flat walls (center-load pallets).
• Don't let slip sheets, plastic wrap or dunnage block airflow. Brace the load so it can't shift into the gaps.

New to reefers? Start with reefer trucking basics.

Reefer fuel, pre-trip and door openings

Pre-trip the unit, not just the truck. Run the unit's own pre-trip test and note the date and time. The UF/IFAS handbook calls a documented reefer pre-trip a key part of a sanitary transportation plan and of fighting claims. Also check door seals, the air chute, floor drains and that the trailer is clean, dry and odor free. Add it to your pre-trip inspection checklist.

Reefer fuel. In summer the unit works harder, so start every load with a full reefer tank and know where you'll fill next. IRS Publication 510 treats fuel burned in a separate motor that runs a refrigeration unit as an off-highway business use, which is why many reefer tanks run on dyed (off-road) diesel. Dyed fuel is for nontaxable uses only, so it never goes in the tractor's tank. Keep reefer fuel receipts apart from tractor fuel.

Door openings and multi-stop loads. Every door opening lets hot, humid air in. UF/IFAS notes that moisture condenses on cold cartons when doors open for delivery stops in warm weather, which can soak boxes. On multi-stop loads:

• Ask the shipper to load in stop order so you don't dig through the load.
• Back in and seal to the dock before you open the doors when you can.
• Open only as long as needed, then let the unit recover before the next stop.
• Take pulp temps on what's left on board after each stop and note them.

If the receiver rejects the load

Under the FDA rule, the receiver checks for temperature abuse by looking at the food's temperature, the trailer's air temperature and setting, and a sensory check such as off odors. If anyone sees signs of a possible temperature control failure, the food can't be sold unless a qualified person decides it is still safe.

The UF/IFAS handbook warns that rejections are often based on air temperatures recorded outside the cartons, not the product inside, which can lead to unwarranted rejections. So your evidence matters:

1. Stay calm and don't leave. Call your dispatcher and the broker right away.
2. Ask for pulp temperatures taken in front of you, at several spots, and write them down.
3. Download the unit's data: setpoint, return and discharge air, mode, alarms and door events. Under the FDA rule this is how a carrier shows it held temperature.
4. Gather your paper: BOL with your loading notes, pre-trip record, photos at pickup, seal number.
5. Get the rejection in writing with the reason, and follow the broker's instructions on where the load goes next.

Then notify your insurer quickly. Our cargo claims guide walks through the claim process step by step.

Summer heat and the driver

Your trailer is cold, but you aren't. Waiting at hot docks, checking pulp temps, fueling and climbing in and out add up. OSHA's heat guidance comes down to water, rest and shade, both to prevent heat illness and to treat it.

• Drink before you're thirsty. NIOSH recommends about 1 cup (8 oz) of water every 15 to 20 minutes during moderate activity in the heat, and generally no more than 6 cups an hour. If you sweat for hours, add drinks with electrolytes. Skip alcohol and drinks high in caffeine or sugar.
• Ease in. OSHA says people new to the heat, or back after time away, need time to build tolerance. The first hot days of the year are the riskiest.
• Check the heat index. The OSHA-NIOSH Heat App for phones calculates it. OSHA notes it gives heat index only, not a full heat measurement.

When the heavy produce season hits

USDA's Agricultural Refrigerated Truck Quarterly tracks fresh produce moved by truck. Its numbers show how volume and origins shift with the seasons:

What it means for a small reefer operation:

• In summer, more produce loads out of California and the West, and the loads that move most are the ones that need tight temperatures and continuous airflow.
• Summer volume and summer heat arrive together. That's when pre-cooling time, reefer fuel and pulp temp checks matter most.
• Plan your reloads before you head into produce country, so a good outbound load doesn't turn into a long empty return.

See the freight market calendar for the full year, or let our reefer dispatch team plan the lanes for you.

Questions carriers ask