Autoclave pound is a unit used to describe the amount of air that is removed from the autoclave during the vacuum cycle of the sterilization process. The negative pounds or vacuum level, is what is important to achieve steam sterilization. Most sterilizer chamber manufacturers use the term bar for vacuum reading to ensure it reaches its full rated vacuum requirement to enable full steam penetration.

This is achieved by utilizing a vacuum pump to extract the air from the chamber, which facilitates efficient steam sterilization. The autoclave pound denotes the amount of pressure, typically measured in pounds per square inch (psi) or bar, that the vacuum pump can generate.

The effectiveness of the sterilization process relies heavily on the ability to remove air from the autoclave chamber. Since steam at lower temperatures is less effective in killing microorganisms compared to higher temperatures, it's crucial to remove as much air as possible to ensure that steam can reach all the surfaces and penetrate any wrapped items or porous loads within the chamber.

The typical vacuum levels or negative pressure measured in autoclaves during the sterilization cycle range from -13 to -30 psi (-0.9 to -2.1 bar). By achieving adequate negative pressure levels, the steam can rapidly permeate and effectively sterilize the items inside the autoclave.