This sterilisation method uses steam produced by an electric boiler with an air outlet at the bottom and a steam outlet at the top.

• A. Vertical downward displacement autoclave
• B. Horizontal autoclave
• C. Gravity displacement autoclave
• D. Pre-vacuum autoclave

Answer: (A)

The key idea is how air is removed so steam can contact every surface. In a vertical downward displacement autoclave, steam is produced by an electric boiler and the design directs air to be pushed downward and out through a bottom outlet, while steam rises and fills the chamber from the top. This arrangement achieves effective sterilization by gravity-driven displacement of air, without needing a vacuum system. The setup described—air outlet at the bottom and steam outlet at the top—fits this vertical downward displacement arrangement, which is why it’s the best match. The other designs either rely on vacuum to remove air or are simply different orientations, not the same downward-displacing mechanism.