If you're serving food in temperatures over 90 F, such as a picnic, limit the time in which food sits out to one hour or less. Don't hesitate, refrigerate . . . Perishable foods include meat, poultry, fish, dairy products, pasta, rice and cooked vegetables. Leave the covers off containers cracked open to help food cool faster. Cover tightly once the food is cooled.
Food cools more rapidly in shallow containers, limiting the growth of bacteria.
If you leave your pizza and other perishable foods at room temperature for more than a couple of hours, TOSS them out. Some types of bacteria can form a heat-resistant toxin that cooking can't destroy. Don't reheat take-out food in its original container in the microwave, unless the container is described as safe for microwave use. Chemicals from carryout containers can be absorbed into foods at high temperatures. Safe containers for microwave cooking include glass and glass ceramic cookware, and those labeled for microwave use.