Heat sterilization physical indicators

Each heat sterilization cycle should be recorded by appropriate equipment with suitable accuracy and predsion, e.g., on a time/temperature chart with a suitably large scale. The temperature should be recorded from a probe at the coolest part of the load or loaded chamber, this point having been determined during the validation the temperature should preferably be checked against a second independent temperature probe located at the same position. The chart, or a photocopy of it, should form part of the batch record. Chemical or biological indicators may also be used but should not take the place of physical controls. 

Each heat sterilization cycle should be recorded on a temperature-time chart or by other suitable automatic means. The time-temperature record should form part of the batch record. Chemical or biological indicators may be used in addition to but should not take the place of physical controls. 

The duration and temperature of heat sterilization must be recorded. The temperature must be determined at the coldest site in the lot or the chamber. The observations form a part of the Lot Production Record. Chemical or biological indicators may be used but not in place of physical controls. 

Hospital sterilizer loads vary in composition, thus the challenge presented to the test organism can vary considerably, depending on the type and contents of packages in which they are placed. The benefits of a standardized test-pack constmction and test protocol are obvious, and such recommendation is made by AAMI for steam and ethylene oxide sterilizers (11). More recentiy in European (CEN) and International (ISO) standards, biological indicators are considered as additional information supplemental to the measurement of physical parameters. Indeed, for sterilization using moist heat (steam), the biological indicator information is not considered to be relevant. 

Biological castles are employed during heat penetration situations in order to demonstrate the degree of process lethality provided by the sterilization cycle. Calibrated biological indicators utilized for this purpose function as bioburden models providing data that can be utilized to calculate Fq or substantiate and supplement physical temperature measurements obtained from thermocouples. 

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