Yes, the DOT has a regulation regarding air conditioning in tractor trailers. It is found in the Federal Motor Carrier Safety Regulations (FMCSRs) under Part 393.77. This regulation states that every truck manufactured on or after July 1, 1994, and used to transport property must be equipped with an air conditioning system that is capable of maintaining the driver's compartment at a temperature of 72 degrees Fahrenheit (22 degrees Celsius) or less when the outside temperature is 100 degrees Fahrenheit (38 degrees Celsius).
The regulation also specifies that the air conditioning system must be able to cool the driver's compartment to 72 degrees Fahrenheit within 15 minutes of the engine being started. If the air conditioning system fails to meet these requirements, the truck must be taken out of service until it is repaired.
