Temperature records, heat sterilization

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. 

Dry-heat sterilization is generally conducted at 160—170°C for >2 h. Specific exposures are dictated by the bioburden concentration and the temperature tolerance of the products under sterilization. At considerably higher temperatures, the required exposure times are much shorter. The effectiveness of any cycle type must be tested. For dry-heat sterilization, forced-air-type ovens are usually specified for better temperature distribution. Temperature-recording devices are recommended. 

Dry heat sterilization is usually carried out in a hot air oven which comprises an insulated polished stainless steel chamber, with a usual capacity of up to 250 litres, surrounded by an outer case containing electric heaters located in positions to prevent cool spots developing inside the chamber. A fan is fitted to the rear of the oven to provide circulating air, thus ensuring more rapid equilibration of temperature. Shelves within the chamber are perforated to allow good air flow. Thermocouples can be used to monitor the temperature of both the oven air and articles contained within. A fixed temperature sensor connected to a chart recorder provides a permanent record of the sterilization cycle. Appropriate door-locking controls should be incorporated to prevent interruption of a sterilization cycle once begun. 

In heat sterilization processes, a temperature record chart is made of each sterilization cycle with both dry and moist heat (i.e. autoclave) sterilizers this chart forms part of the batch documentation and is compared against a master temperature record (MTR). It is recommended that the temperature be taken at the coolest part of the loaded sterilizer. Further information on heat distribution and penetra-... 

Chamber temperature should be controllable and monitored throughout all cycles. The temperature obtained in a load is a function of the initial product temperature and Its specific heat, the amount of steam injected, and the effectiveness of the insulation or the jacket at preventing heat loss. Temperature during the exposure phase of ethylene oxide sterilization cycles is not controlled by steam injection into the chamber as occurs in thermal sterilization. Loss of temperature may be compensated for by steam Injection into the jacket. The control probe is usually located within the chamber rather than within the jacket, and control of temperature is a good deal less fine than ini steam sterilizers because of the slower response through the jacket. Ethylene oxide sterilizers should be equipped with both jacket and chamber temperature indicators, and with chamber temperature recorders. Sterilizers should be specified with access... 

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. 

Sterilization by moist heat is suitable only for water-wettabie materials and aqueous solutions. Both temperature and pressure should be used to monitor the process. The temperature recorder should normally be independent of the controller, and there should be an independent temperature indicator, the reading from which is routinely checked against the chart recorder during the sterilization period. For sterilizers fitted with a drain at the bottom of the chamber, it may also be necessary to record the temperature at this position, throughout the sterilization period. There should be... 

Each heat sterilization cycle should be recorded on a time/temperature chart with a suitably large scale or by other appropriate equipment with suitable accuracy and precision. The position of the temperature probes used of controlling and/or recording should have been determined during the validation, and... 

Records of sterilization in case of parenteral preparations which are heat sterilized including particulars of time, temperature and pressure employed. Such records should be marked to relate to the batch sterilized. 

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. 

Each heat sterilization cycle should be recorded on a temperature-time chart or by other suitable automatic means. 

The relationship between temperature and pressure holds true only in the presence of pure steam adulteration with air contributes to a partial pressure but not to the temperature of the steam. Thus, in the presence of air the temperature achieved will reflect the contribution made by the steam and will be lower than that normally attributed to the total pressure recorded. Addition of further steam will raise the temperature but residual air surrounding articles may delay heat penetration or, if a large amount of air is present, it may collect at the bottom of the sterilizer, completely altering the temperature profile of the sterilizer chamber. It is for these reasons that efficient air removal is a major aim in the design and operation of a boiler-fed steam sterilizer. 

Again, bacterial spores are much more resistant than vegetative cells, and their recorded resistance varies markedly depending upon their degree of dryness. In many early studies on dry heat resistance of spores their water content was not adequately controlled, so conflicting data arose regarding the exposure conditions necessary to achieve effective sterilization. This was partly responsible for variatiorrs in recommended exposure temperatures and times in different pharmacopoeias. 

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