(a) Refrigeration units or effectively insulated units shall be provided in such number and of such capacity to assure the maintenance of potentially hazardous food at required temperatures during storage. Each mechanically refrigerated unit storing potentially hazardous food shall be provided with a numerically scaled indicating thermometer, accurate to plus or minus 3°F (congruent to plus or minus 1°C). The sensing element shall be located to measure the air temperature in the unit at a location that is representative of the air temperature in the unit. The thermometer scale shall be located to be easily readable. Recording thermometers, accurate to plus or minus 3°F (congruent to plus or minus 1°C) may be used in lieu of indicating thermometers. In lieu of a thermometer, portable refrigeration units which rely on contact with refrigerated surfaces rather than airflow shall have product temperature monitored at sufficient frequency to ensure proper temperature.

(b) Potentially hazardous frozen foods shall be kept frozen and shall be stored at an air temperature of 0°F (congruent to minus 18°C) or below except for defrost cycles and brief periods of loading or unloading.

(c) Ice used as a cooling medium for food storage shall not be used or sold for human consumption.