Effects of Non-Condensable Gases (NCGs) on Steam Sterilisation Processes

Read the full textEffects of Non Condensable Gases on Sterilization


A gravity displacement (class N) steam sterilization process can not reliably remove gases from hollow or porous items, resulting in areas that do not get sterilized, and the failure of the load. They should not be used for body jewelry, needles, tattoo tubes or textiles.


395 CENTRAL SERVICE Volume 13 2005


Effects of Non-Condensable Gases (NCGs) on Steam Sterilisation Processes

U. Kaiser


  • steam sterilisation process
  • non-condensable gases (NCGs)
  • process challenge device (PCD)


The dangers posed by non-condensable gases (NCGs) in steam sterilisation processes have long been underestimated. Biological indicators, or the best chemical indicators on the market, do not signal the presence of a NCG content of up to 10% in a sterilisation process so long as there is mixing of steam and NCGs in the sterilisation chamber.

Already back in 1963, Bowie and Dick (1) demonstrated that steam/NCG mixtures could prove dangerous if steam resulting from condensation is being consumed on the sterile supplies and the NCGs enclosed in this steam are able to accumulate present in the form of closed packages.

If the NCGs are unable to mix again with steam within closed packages containing instruments, in porous laundry packages or within lumened devices, these quantities of gas will accumulate and prevent steam penetration into these areas, thus also preventing the build-up of heat and entry of water which are prerequisites for successful sterilisation.

Statim helix containing Class 6 emulating indicator in 2000 tray
Statim helix process control device for validation of air removal containing Class 6 emulating indicator in 2000 tray

* Dr. Ulrich Kaiser, Member of the working group ISO TC 198 WG 4+6 (Modification of the Euro ISO standards for chemical and biological indicators), gke-mbH, Auf der Lind 10, 65529 Waldems-Esch, Germany, E-Mail: office@gke-mbh.de

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