Question: what factors determine the time period necessary for steam-pressure sterilization?
Answer: Time. The exposure (sterilization) time is a critical factor simply because all the organisms do not die at the same time. ... 
Temperature. The second critical factor in steam sterilization is the temperature of the saturated steam controlled in the chamber of the sterilizer. ... 
Moisture. ... 
Direct Steam Contact. ... 
Air Removal. ... 
Drying.