The USDA has a whole page dedicated to what they've called the "Danger Zone." Do you know what that is, and how it relates to food safety? It's worth knowing this important temperature zone and what happens when food is within this range.
Kitchen Fact: Bacteria grows most rapidly between 40°and 140°F, so food should be kept either above or below this temperature range.
We've talked about how long cooked foods can be left out unrefrigerated (two hours or just one if the temperature's above 90°F), and this is because the food is probably sitting in a temperature that's within what the USDA dubs the "Danger Zone." This zone, which is between 40° and 140°F, is where harmful bacteria grows rapidly and can even double in as little as 20 minutes.
How do you keep foods out of the danger zone? Keep cold foods refrigerated or on ice to stay below 40°F, or for hot foods, use appliances such as slow cookers or chafing dishes to keep them hot and above 140°F.
Kitchen Fact Source: "Danger Zone" (40 °F - 140 °F) at USDA.gov