INFECTION PREVENTION AND CONTROL
follows: ‘Wet spots or patches on the packaging show that liquid water has been drawn into the chamber. There are several possible explanations, including: n poorly draining steam traps between the steriliser and boiler (a sudden demand for steam can draw water out of a full trap);
n severe pressure fluctuations in the main; n priming of the boiler leading to carry- over of water in the steam.’
In addition to causes such as overloading of the steriliser, it is evident that poor quality steam, outside the specification detailed in BS EN 285, is a likely factor.
Evidence of wetness
If there is evidence of wetness on the packaging when removed from the sterilisers, typically highlighted by the presence of darkened patches, the pack will need to have the damp wrapping removed and replaced with new. Then the pack will have to be put through the sterilisation process again. This, of course, could affect more than one pack in a batch. In addition to the reprocessing, there will be time and effort spent on establishing the cause of the problem. Key stakeholders within CSSDs can mitigate against increased processing times and costs, not to mention increased patient risk, by ensuring that the sterilisation process is not impeded by poor quality steam. The use of high- quality steam is emphasised in HTM 01-01. By using specific steam-to-steam generators that use a high quality water supply (typically reverse osmosis), an HTM-compliant header, and a well- designed distribution system, steam quality can be best improved to reach a dryness level above 95%, as stipulated in BS EN 285. Not only can the correct clean steam generator installation have an impact on dryness levels, but it also reduces the risk of introducing contaminants into the sterilisation process.
Surely steam is clean? Surely, however, steam is clean, wherever it comes from? Well, the evaporation process certainly gives steam a broad element of ‘cleanliness’, but when we consider direct use applications such as pharmaceutical manufacturing, food processing, or hospital sterilisation, there are in fact different grades of steam, which are influenced by the water quality used, and the materials and design of the generation plant and distribution system. This all
Table 1. Sterilisation temperature bands. High temperature steam Sterilisation temperature [˚C]* Maximum temperature [˚C] Maximum holding time [min]
121
124 15
134 137 3
*The temperature setting on the automatic controller will not generally be the sterilisation temperature, but a higher temperature within the sterilisation temperature band.
Time-temperature relationships are shown as per HTM 01-01 part C.
influences the purity of the steam, which can be measured by the level of contaminants present in the condensate that is formed.
Clean steam generators (often referred to as Chemical Free Steam Generators) use regular plant steam as the primary thermal energy source to boil a clean water supply (such as reverse osmosis water) into steam that is free of harmful substances and impurities. The heat exchange is indirect, via a steam heating coil, so the plant steam never comes into direct contact with the clean steam. This high-quality steam can then be applied directly to the sterilisation process. Clean steam generators can help CSSD departments take a quality and ‘patient first’ approach in the sterilisation of reusable medical devices. Fundamentally, sterilisation must be right first time, every time, to safeguard patient health and ensure that sterile services run as smoothly as possible. By implementing a CSG system that delivers dedicated high-
quality steam for the sterilisation process, healthcare facilities can better control the quality of their steam supply to protect against ineffective sterilisation.
Specifically developed
The Spirax Sarco clean steam generator (Fig 2) for Healthcare has been specifically developed for sterilisation applications, with the aim of delivering steam of a quality that exceeds the standards set out in BS EN 285. This latest unit draws on the experience of decades in the manufacture of clean steam generators, and implements innovative thinking in relation to degassing of the water. The result is a unit that delivers repeatable high-quality steam under a variety of operating conditions which exceeds the minimum steam dryness value of 95%, as well as reducing the level of non-condensable gases (as outlined in BS EN 285).
Figure 2: The Spirax Sarco clean steam generator for Healthcare has been specifically developed for sterilisation applications, with the aim of delivering steam of a quality that exceeds the standards set out in BS EN 285, and thus ensuring reliable and consistent sterilisation of reuseable medical devices.
38 Health Estate Journal April 2021
Steriliser operation has a particularly ‘peaky’ steam load profile, with the load high at certain points of the cycle, and then instantaneously dropping to low flow rates at other points. The latest monitoring equipment utilised by Spirax Sarco shows that the dryness output from its latest generator exceeds the BS EN 285 recommendations throughout these dynamic changes in load, ensuring that high quality is delivered continuously throughout the sterilisation cycle. When trying to trace the cause of wet packs on existing plant, this is something that is particularly difficult to assess. The common dryness testing regime is based on a point in time, and is not continuous, so identifying wet steam can be somewhat ‘hit and miss’, and dependent on the operating conditions prevailing at the time of the test. This latest generator can therefore safeguard against issues
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