Final answer:
Cooking appliances with a fire box of 5 ft³ or less should have an efficient device to prevent heat from escaping through the chimney, thus improving heat retention and fuel efficiency.
Step-by-step explanation:
The question implies a regulation or standard pertaining to cooking appliances, specifically those with a fire box of 5 ft³ or less.
Such appliances should be equipped with an efficient device that prevents heat loss, typically by limiting the amount of heat escaping through the chimney.
This may be referring to a baffle, a heat exchanger, or some other form of technology designed to improve the efficiency of the appliance by retaining heat within the cooking area and reducing fuel consumption.