A wide variety of gas ovens are used in modern homes, including freestanding ranges and wall ovens. The preheating functions differ across the many brands and models. Most gas ovens are equipped to detect when the oven cavity reaches a specified temperature, and then to automatically adjust the combustion rate as needed to maintain that temperature. Some gas ovens may signal in a variety of ways that they have reached the desired temperature, while others may not signal at all.
Look for static symbols and indicators on the oven's LCD screen and control panel. Modern displays might show the full word as "Preheating" or abbreviate it down to "PrE." When these visual indicators disappear, that commonly means that the preheating cycle has reached the desired temperature.
Monitor the animated timers and symbols on the LCD display. The oven starts the preheating stage from room temperature, and preheating ends when the specified temperature is reached. Some LCD displays show a series of bars that light up in ascending order, like stairs, as the oven temperature rises. The screen might also display the oven temperature in degrees Fahrenheit or Celsius as it increases toward the goal.
Obtain an oven thermometer that stands or hangs inside the oven to check on the accuracy of the oven's temperature controls. You generally have to monitor the temperature arrow through the glass oven door. These are different from the temperature probes you can use to measure the internal temperature of meats and poultry to determine when they are properly cooked.
Listen for beeps or tones before, during or after the preheating cycle. Many modern gas ovens use electronic controls and push-button pads. Shorter beeps and tones occur when you press a number button. A longer tone may signal the end of a phase such as preheating.
Listen for the sound of internal fans in the gas oven, if the oven is so equipped. Such fans may be activated after sensors detect that the oven cavity has achieved the set temperature. Convection cooking uses fans to evenly disperse heat throughout the oven cavity. Some advanced gas convection ovens offer "full cavity" preheating that ensures the physical oven components, such as the racks and walls, all have reached the specified temperature.
Use the oven immediately upon turning it on, if the oven is designed for such use. Many modern gas ranges can rapidly preheat the oven cavity. Some high-tech models feature sensors that monitor temperatures in real time and can dedicate extra energy to quickly raising the temperature.