Clarifying Dwell Versus Contact Time
A reader writes: “In a recent class you tried to explain the difference between dwell time and contact time, but I am still confused. Could you clarify?
Sorry for the confusion. This confusion is partly due to the reality that these terms are oftentimes used interchangeably in the custodial world. Some of you may disagree with my definitions, which is okay by me so long as we can stay friends and possibly agree to disagree on some points. I do not have a dog in this fight and too often, may oversimplify a subject that would require a lot more space than I have in this brief article to address.
That is one reason I hope that my articles will generate discussion, use of a search engine and further clarification. To me, such a response is furthering the discussion in a positive, professional manner. The following are my preferences at the current time, subject to correction as I continue to learn about this and other custodial related issues.
I prefer to use the term “dwell time” as it addresses the recommended time for a disinfectant be effective in its prescribed “kill rate.” Oftentimes, the label will require 2 to 10 minutes dwell time while remaining wet. Of course, the disinfectant must be mixed and used properly to be effective. Usually the directions will then require removal using appropriate processes and tools to achieve the desired kill rate.
I prefer to use the term “contact time” for scrubbing or stripping finish from hard floors that need to be refurbished. Please note that this is NOT disinfection; rather time to emulsify a floor finish or seal. Again, the label may require 5 to 10 minutes for the floor to remain wet for the stripper to totally emulsify the water-based finish on the floor that is to be removed. This process usually requires using a stripping pad with appropriate speed floor machine to mechanically strip and mix up the solution before it is vacuumed up while still very wet.
What if you or others decide to use different definitions? That approach is fine with me so long as you try to be consistent and everyone at the table understands what you are talking about.
Your comments and feedback are always appreciated. I hope to hear from you soon. Until then, keep it clean…
Mickey Crowe has been involved in the industry for over 35 years. He is a trainer, speaker and consultant. You can reach Mickey at 678-314-2171 or CTCG50@comcast.net.