Fuel cell oxygen electrode and instant startup fuel cells employing such oxygen electrode. At least two moveable clamps are arranged peripherally in even spaced-apart relationship, for clamping the lid and the pouring rim, when the steam pressure cooker is closed, and clearing the pouring rim, when the steam pressure cooker is opened. Some of the image sensor pixels may form a calibration sensor and some of the image sensor pixels may form an imager. In the steam generation portion, the steam-generating composition is held or sandwiched in a support so as to inhibit the movement of the steam-generating composition inside the steam generation portion, and the steam generation portion itself is formed into a sheet. A pressure is exerted by the bladder onto the leg through the body weight applied to the base pad when the foot is loaded.