Contact Times for Surface Disinfectants

Contact Times for Surface Disinfectants

“Follow the path of the unsafe, independent thinker. Expose your ideas to the danger of controversy. Speak your mind and fear less the label of “crackpot” than the stigma of conformity,” Thomas J. Watson

I cringe when I read a LinkenIn post recently. The post stated, “The definition of Dwell (Contact) Time is ‘time spent in the same position, area, or stage of a process.’ When applying this to disinfection processes, its the most important aspect of the disinfection process and the least paid attention too. We spray we wipe we go…. electrostatic technology allows for a complete coverage of a surface without the need to wipe it off, which allows for the dwell time to do its thing…which is kill viruses and bacteria… if your disinfectant says it has a 10 minute dwell time and you spray and wipe and go what are you really disinfecting?” The author, like the majority in the cleaning and disinfection business, believe that a disinfectant’s dwell time (as stated on the label) must be maintained in order for the “kill claims” to be valid.

Call me a “crackpot” if you wish, but here’s an idea for your consideration… Contact/dwell times are meant for EPA registration of disinfectants, not for killing specific pathogenic organisms on pre-cleaned surfaces.

“Cleaning is the necessary first step of any disinfection process. Cleaning removes organic matter, salts, and visible soils, all of which interfere with microbial inactivation. The physical action of scrubbing with detergents and surfactants and rinsing with water removes substantial numbers of microorganisms. If a surface is not cleaned first, the success of the disinfection process can be compromised. Removal of all visible blood and inorganic and organic matter can be as critical as the germicidal activity of the disinfecting agent.” CDC Cleaning and Disinfecting Environmental Surfaces

Washing or scrubbing a surface physically removes soil and organic materials such as blood and body fluids, and takes with it many germs. One of the greatest weapons in the war against harmful microorganisms is microfiber (micro denier) mops and cleaning cloths. A microfiber cloth helps physically remove the food and moisture necessary for microorganisms to survive, but better grades of microfiber (those with very dense weaving and fiber configuration) can even remove large quantities of microbes, including hard-to-kill spores. If 99% of the organic soil can be removed from an environmental surface or piece of patient-care equipment with a micro denier cloth and the hospital-approved disinfectant, then labeled dwell times are not as critical.

The difference between the “real world” and the lab where disinfectant dwell times are established, is that in the real world, there is a physical removal of soil along with the mechanical friction that wiping provides (i.e., good old fashioned “elbow grease”).

Dr. William Rutala (APIC Annual Ed Conference 2005), states that a 6 log reduction happens in the initial 60 seconds the disinfectant (phenolic, quat or bleach) is applied to pre-cleaned surfaces. After that first 60 seconds, the log reduction plateaus through 10 minutes. There are at least 14 scientific studies proving the same thing that Rutala discovered.

Rutala also stated that if a surface dries in 2-3 minutes, that means that the same surface would have to be re-wetted 4 additional applications in order to provide the “per label” 10-minute contact time. That 10 minute contact time is meant for EPA registration, NOT the time it takes to kill microorganisms on pre-cleaned surfaces.

Now for the legal disclaimer: By law, users must follow all applicable label instructions for EPA-registered products. Ideally, product users should consider and use products that have the shortened contact time.

Here’s your call to action…

Environmental Services leaders and Infection Preventionists should work together in their facility to perform an IP Risk Assessment that documents the fact that the hospital-approved disinfectant, when applied with a micro denier cloth and allowed to dry (not necessarily the product’s labeled dwell time), will render surfaces and equipment free of pathogens in sufficient numbers to prevent human disease (i.e. hygienically clean). The risk assessment should demonstrate that the combination of product and practice resulted in effective surface disinfection, including the reduction of patient risk via microbial removal and inactivation as well as improved patient outcomes.

About Darrel Hicks

J. Darrel Hicks, B.A., is the author of Wiley Publishing's "Infection Prevention For Dummies", and is nationally recognized as one of the top experts in infection control. Darrel Hicks is also the Past President of the IEHA and is an active member in AHE where he holds the designation of CHESP. View all posts by Darrel Hicks

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