To provide a high safety equipment and its control method for directly controlling the flow of air in each chamber to keep the flow in one direction, by controlling the amount of exhaust air from each chamber, without controlling a chamber pressure difference among a front chamber, a working chamber, and an experimental cabinet of the high safety equipment.

A high degree safe equipment 1 comprises a front chamber 22, a working chamber 21 connected to the front chamber 22 through a door 23, and an experimental cabinet 24 that is located in the working chamber, and is communicated with the working chamber through a door, the opening of which is adjustable, and further involves a contaminant substance therein. There are provided fixed type dampers 2, 2' connected with the front chamber 22 and the working chamber 21, a predetermined air amount apparatus 3 connected with the front chamber, and variable air amount type predetermined air amount apparatuses 4, 5 connected with the experimental cabinet 24. A ratio of exhaust air amounts of the working chamber and the safe cabinet is controlled, interlocking the adjustment of the degree of the door of the experimental cabinet, while keeping the total exhaust air amount of the working chamber and the experimental cabinet.