What type of sterilisation used an electric boiler to create steam and has an air outlet at the bottom and steam outlet at the top?

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

Answer: (A)

Air is removed from the chamber by gravity rather than by a vacuum, with steam generation provided by an electric boiler. In a vertical downward displacement autoclave, steam is drawn in from the top and begins to push air downward; the displaced air exits through a bottom outlet while steam continues to fill the chamber and eventually vents as needed from the top. This arrangement—air outlet at the bottom and steam outlet at the top—fits the vertical downward displacement design, which relies on gravity to purge air and ensure steam contact with all surfaces.

Other designs differ: horizontal units can use the same gravity principle but aren’t defined by this bottom-versus-top outlet pattern, and pre-vacuum autoclaves remove air with a vacuum pump instead of gravity displacement, so their air and steam venting arrangement isn’t described this way.