How long can a hot-held TCS food remain in the "Temperature Danger Zone" before it must be served or thrown out?

The Temperature Danger Zone is the range of temperatures between 41°F and 135°F, in which bacteria can grow rapidly and cause food poisoning. It is important to keep hot-held TCS foods at a temperature of 135°F or higher to prevent the growth of bacteria. If the food drops below 135°F for more than 4 hours, it must be thrown out.