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IDI - Irish Decontamination Institute

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Central Service - Issue 6/2012

Central Service - Issue 6/2012

Central Service - Issue 6/2012


  • What's New in Standardisation: Drafts
  • The Institute of Decontamination Sciences (IDSc) Annual Conference 2012
  • David Hurrell
  • A new member for the Central Service Editorial board
  • Validation of small steam sterilizers in the healthcare sector according to ISO 17665-1


J.P.C.M. van Doornmalen, R. J. Hermsen and K. Kopinga:
Six commercially available Class 6 Chemical Indicators tested against their stated values

Objective: To assess whether ISO 11140 part 1 class 6 Chemical Indicators (CI s) for steam sterilization actually meet their claimed Stated Values (SVs). SVs for steam sterilization represent a temperature-time combination at which the CI has to give an unambiguous pass result, e. g. at 134 C after 3.5 minutes in saturated steam.
Design: Six types (brands) of commercially available ISO 11140 part 1 class 6 CI s were purchased and investigated. These CI s were exposed to saturated steam at 134 C. The exposure time was varied from 1 s to 15 minutes. At the SVs of the indicator it has to show an unambiguous color change towards the reference color. This color change indicates a pass result.
Method: After exposure of the CI s to saturated steam the indicator ink and the reference color on the CI strip were read out immediately. To avoid observer-dependent results these readings were obtained from a spectrodensitometer.
Results: Only one type of the six class 6 CI s actually reached its reference color and showed a color change close to its SVs.
Conclusions: Class 6 CI s have only a very limited added value and in most cases their use may lead to conclusions that are unreliable and even unsafe.

steam sterilization monitoring Class 6 Chemical Indicators ISO 11140


Recommendations by the «Quality Task Group»: DGSV Flow Chart 2012 for Classification of Medical Devices

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