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Last Modified: Tuesday, July 06, 2021

Hot Air Tunnel Validation

Dry heat is sometimes used for sterilization instead of the much more efficient moist heat
because some materials are sensitive to moisture.

Dry heat is often used to ensure that glass and other laboratory equipment is free of pyrogenic material.

The process of sterilization within a hot air tunnel is a critical process and there is a regulatory requirement for validation of the process in most countries. Although validation requirements and quality assurance requirements vary in detail, the common theme is that it must be shown that sterilization has been achieved. Validation is defined as the documented procedure of obtaining, recording and interpreting results to ensure that the sterilization process has been and will be consistently effective.

Thermal validation consists of accurately measuring the temperature at critical points within the sterilization chamber throughout the process. Dry heat generally employs a temperature between 250°C and 400°C for varying time. The sterilizer is required to heat all parts of its load up to the specified temperature for a specified period long enough to achieve the desired sterility. The confidence of degree of sterility can then be expressed by a lethality formula or ‘thermal death time’. TQSoft™ thermal validation systems can automatically calculate and alert critical operational parameters with its Interval Calculations feature.

Problems with sterilization can occur with the spread of temperatures within the load. It is essential to identify the coolest and hottest part of the load and calculate deviations and fluctuations. Many companies have their own ideas on analysis, and TQSoft™ thermal validation systems can provide flexibility with its Interval Calculations feature.

The accuracy of the sensors and data acquisition hardware used to perform thermal validation is critical. Calibration and Calibration Check operating procedures are indispensable to normal acceptable validation practice, no matter what sensors are used (RTD’s, thermistors or thermocouples). The validation report must show that thermocouples, sensors, calibration and data acquisition equipment have been checked against a traceable standard at regular intervals. Thermocouples should be checked before and after a validation study. RTD’s and thermistors require less frequent checking, usually periodically every 6 months.

For dry heat, accuracy is generally required to be +/- 1.0°C.

TQSoft™ thermal validation software can help achieve these accuracies by providing simple to operate, automated calibration and calibration checking procedures and reports. TQSoft™ also stores all validation and calibration equipment details in a Test Equipment Database management system. Before a validation study the engineer can tick the items of equipment in use and TQSoft™ stores this information in each validation record. This allows users to create audit reports on individual items of the calibration or validation equipment.

Thermocouples have a limited life span and remote logger batteries can run low causing expensive problems during the validation process. TQSoft™ thermal validation software tracks thermocouple and logger usage and allows engineers to set limits.

Because of the variety and variation of processes run within sterilizers, validation engineers should have a method to store test parameters and calculations to be able to repeat tests and reproduce reports quickly and efficiently. This is periodic revalidation. TQSoft™ thermal validation systems provide a database of ‘Test Specifications’ which can be re-used and easily adapted to new requirements.

TQSoft™ thermal validation software provides a Reporting and Report Management module which can provide a large degree of automation to report production, and allow reports to be built, managed, converted to PDF, emailed and archived.

TQSoft™ thermal validation software provides compliance with FDA regulation on electronic signatures in 21CFR Part 11 and has been developed and maintained according to GAMP.

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