DRY OR WET? If you moisten a surface with a disinfection product, the liquid film will air dry for a certain time. During this process the product is effective. The question is whether it still works once the surface is dry? And is the contact time specified by the manufacturer, the time between the wet and dried surface (wet contact time) or does a certain time span also count as long as the dried product is effective,...if at all. This is important because the latter is difficult to prove and there is very limited scientific research available. One of the few studies related to this subject is, for example, a study published in 2021 (3) on the bactericidal effect of “ready-to-use” disposable disinfection wipes, concludes that there is no additional bactericidal effect after drying of the disinfectant liquid film. WET CONTACT TIME IS WHAT COUNTS From the above, it is clear that the contact time specified by the manufacturer refers to the wet contact time. There are US and European guidelines that either do not mention contact time at all or talk about contact time but do not define the term. However, most organizations advising the pharmaceutical industry define the term as wet contact time: the time between the, visually observed, moist and dried surface.
WHAT DRIES UP FIRST IS DEC I S I VE
When using a disinfectant, the contact time prescribed by the manufacturer should be respected. Slightly longer is not a problem, shorter is not acceptable. Otherwise, there is a risk of not killing enough micro-organisms and the contamination risk is not, or not sufficiently, eliminated. As mentioned above, the contact time is simply the drying time of the disinfectant liquid film applied to the surface. However, a surface is never completely dry from one moment to the next which makes it a bit more difficult. For that reason, common sense tells us that the first part of the floor that dries determines wether you have met the contact time. The rest of the surface will have a slightly longer contact time, but at least you can be sure that entire surface is disinfected properly. Seems logical to me I would say.
“ There are American and European guidelines that do not talk about contact time at all or where they do talk about contact time, but then fail to define the term. “
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