The indicator number of the barometer in Figure B is 1.2Mpa. When using, press the connecting rod A at the top of the valve with the handle, and the power arm is larger than the resistance arm, which is more labor-saving than pressing directly by hand. The handle is equivalent to a labor-saving lever.
If dry ice (solid carbon dioxide) powder is sprayed, it will sublimate into gas at room temperature, and the sublimation will absorb heat and have a cooling effect.
Therefore, the answer is:1.2mpa; ; Save effort; Sublimation; It sucks.