What is the maximum amount of time allowed for safely reheating food

It really depends on what food you cook but then it's normally, 2 hours of cooking food  after it is removed from an appliance keeping it hot and warm, leftovers must be refrigerated.As well bacteria grow rapidly between the temperatures of 40°F and 140°F.

                                                        water

a colorless, transparent, odorless, tasteless liquid that forms the seas, lakes, rivers, and rain and is the basis of the fluids of living organisms.

                                                        halon  

any of a number of unreactive gaseous compounds of carbon with bromine and other halogens, used in fire extinguishers, but now known to damage the ozone layer.

                                                  dry chemical

extinguishing agent used on class a, class b, and class c fires.

                                                  carbon dioxide

a colorless, odorless gas produced by burning carbon and organic compounds and by respiration. it is naturally present in air (about 0.03 percent) and is absorbed by plants in photosynthesis.