The boiling point of water at sea level and atmospheric pressure is indeed 212°F (100°C). However, in an autoclave, or any other closed pressure vessel, the boiling point of water can be raised well above this temperature by increasing the pressure inside the vessel.

As the pressure increases, the boiling point of water also increases. This is because higher pressure prevents the water molecules from escaping into the air as steam, so they must reach a higher temperature in order to have enough energy to overcome the increased pressure.

For example, at a pressure of 15 pounds per square inch (psi), the boiling point of water is approximately 250°F (121°C). This is the standard pressure used in most autoclaves for sterilizing laboratory equipment and medical instruments. At a pressure of 30 psi, the boiling point of water is about 275°F (135°C).

Since water cannot change its state in a sealed environment until temperature is achieved to overcome existing pressure inside, temperature will continue to rise to satisfy energy required to change into gaseous state.