The danger zone for food is the temperature range between 40°F (4°C) and 140°F (60°C) . This range of temperatures is where bacteria grow most rapidly, doubling in number in as little as 20 minutes. It is important to keep perishable foods above 140°F or below 40°F (greater than 60°C or less than 4°C) to prevent the growth of harmful pathogens. Food should not be left out of refrigeration for more than 2 hours, or 1 hour if the temperature is above 90°F. Hot food should be kept at or above 140°F, while cold food should be kept at or below 40°F. It is recommended to use a thermometer to check the internal temperature of food to ensure it is safe to eat.