2010 California Code
Vehicle Code
Article 9. Refrigeration Equipment

28000.  Every refrigerator van equipped with one or more doors
designed to lock automatically upon closure shall have at least one
door which can be opened from inside the van as an emergency means of
exit.
   For the purposes of this article, "refrigerator van" means any
motor truck, semitrailer, or trailer, with a fully enclosed cargo
body having an enclosed volume of 15 cubic feet or more, which
utilizes a mechanical refrigeration system to reduce the temperature
within the enclosed portion of the vehicle to 32 degrees Fahrenheit
or less, or which provides refrigeration by the use of dry ice.