Types

Pressure steamers cook foods under a pressure of 15 pounds per square inch (1.05 kg/cm) in high-pressure steamers or 4–6 pounds per square inch (0.28–0.42 kg/cm) in low-pressure steamers. They are operated by a timer, which shuts the equipment off after a preset time. The door cannot be opened until the pressure returns to zero.

Pressureless or convection steamers do not operate under pressure. Jets of steam are directed at the food to speed the heat transfer, just as the fan in a convection oven speeds cooking. The door can be opened any time during cooking.