D.C. Mun. Regs. tit. 25, r. 25-A1524
In a mechanically refrigerated or hot food storage unit, the sensor of a temperature measuring device shall be located to measure the air temperature or a simulated product temperature in the warmest part of a mechanically refrigerated unit and in the coolest part of a hot food storage unit.
Cold or hot holding equipment used for potentially hazardous food (time/temperature control for safety food) shall be designed to include and shall be equipped with at least one (1) integral or permanently affixed temperature measuring device that is located to allow easy viewing of the device's temperature display, except as specified in § 1524.3.
Subsection 1524.2 does not apply to equipment for which the placement of a temperature measuring device is not a practical means for measuring the ambient air surrounding the food because of the design, type, and use of the equipment, such as calrod units, heat lamps, cold plates, bainmaries, steam tables, insulated food transport containers, and salad bars.
Temperature measuring devices shall be designed to be easily readable.
Food temperature measuring devices and water temperature measuring devices on warewashing machines shall have a numerical scale, printed record, or digital readout in increments no greater than one degree Celsius (1° C) (two degrees Fahrenheit (2° F)) in the intended range of use. Pf
D.C. Mun. Regs. tit. 25, r. 25-A1524