The number of dumbwaiters in a structure is the total number of small lifts installed in the structure, which are designed exclusively for cargo and are too small to hold human riders. These are usually used for normal circulation of goods like dishes, food, laundry, or papers within a building.

Each qualifying small cargo lift contributes one to the total. The distinction from a passenger or freight elevator is its exclusive goods function together with its size, which cannot accommodate a rider.

Food, dishes, laundry, and papers are common loads rather than an exhaustive list. A lift carrying other small goods can qualify on the same basis.