Which element is NOT a key element to starting a fire?

In the context of starting a fire, the key elements required are often referred to as the "fire triangle," which includes oxygen, fuel, and heat. Oxygen is necessary for combustion, as it supports the chemical reaction that produces fire. Fuel is the material that burns, which can be anything from wood and paper to gasoline. Heat is essential to raise the temperature of the fuel to its ignition point, allowing combustion to occur.

Water, on the other hand, is not a key element for starting a fire; in fact, it is commonly used to extinguish fires. When water is applied to a fire, it cools the flames and reduces the heat necessary for combustion, effectively removing one of the essential components of the fire triangle. Therefore, while oxygen, fuel, and heat are all critical for starting a fire, water does not contribute to this process and is thus not a key element in starting a fire.