Microbes Must Eat 73 



entire bulk to be in contact with 121° C. for at least the minimum 

 15-minute time period. In general, a liter flask of broth should be 

 kept for 30 minutes under 15 pounds steam pressure, while lesser 

 volumes require shorter sterilization times. Remember, it is not 

 the pressure that kills the organisms, it is the temperature created 



Flow Rcgulato 



Atmosphere 



Sofe»y Valve 



Chamber Gouge 

 Ex'housf Valve 



Chamber Droin 

 ShufOft Valve 



Fig. 16. Steam sterilizer (autoclave). (Courtesy of the American 

 Sterilizer Compamj, Erie, Pennsylvania.) 



by raising steam pressure to 15 pounds above normal atmospheric 

 pressure. To insure that the material in the autoclave is being 

 subjected to live steam under pressure, not merely to a mixture of 

 cold air and steam, rely more upon the reading of the temperature 

 gauge than upon the pressure indicator. After securely fastening 

 the door of the sterilizer, drive out the trapped cold air by allowing 



