Improved Sterilizer Tests
By Dave Ayres and Dave Hill
Getting sterilization temperatures right has brought Edinburgh's Scottish Healthcare Supplies and Isothermal Technology Limited of Southport together.
Scottish Healthcare Supplies Sterilizer Test Group assessed various established methods of on-site temperature calibration and realised there might be shortcomings in commercially available "complete" systems. The guidelines require tests on sterilizer systems to be carried out within a system uncertainty of ±0.5°C but the assessment showed that in many cases "complete" systems could produce a system uncertainty of ±1.0° or worse. (Temperature monitoring in sterilizer systems is critical ensuring that microbiological viability is eliminated from the product).
To reliably achieve an on-site uncertainty of better than ±0.5° C a new method was required. Between Isothermal Technology and SHS a new system has been developed which meets the above requirement - even in a moving ambient! This new system exceeds the requirements of the NHS Guidelines and is the first in the World to be evaluated using the German D.K.D. Accreditation Authorities document on evaluating Portable Temperature Calibration Equipment. The new system consists of a Metal Block Thermal Source and a Thermocouple Referencing System.
Thermocouples used for carrying out performance studies on sterilizers are first calibrated using the thermal source as a variable reference temperature while the thermocouple referencing unit is used to null the thermocouple cold junctions. Using this method instead of conventional means reduces uncertainty by a component of at least ±0.3° C. Both these units have their own UKAS calibrated reference thermometers in them so that the precise calibration conditions for the test thermocouples can be accurately established. It is believed that no other system can offer this level of confidence in the measurements.
The calibrated thermocouples are then used to test the sterilizer and finally re calibrated using the thermal source and thermocouple referencing unit. It is this attention to detail that ensures that the sterilizers tested are within limits and both organisations feel confident that the test equipment will acquire a performance record that will stand the closest scrutiny.
© 2007 Isothermal Technology Ltd V1.005