Demystifying Disinfectant Contact Time for Healthcare Staff

Healthcare Purchasing News • James Clayton

Moving Beyond "Wet" And "Dry"

Effective environmental disinfection in the healthcare setting is imperative to maintaining a low bioburden and helping prevent the spread of healthcare-associated infections. Recent studies have shown that environmental contamination plays an important role in the transmission of Methicillin-resistant Staphylococcus aureus (MRSA), Carbapenem- resistant Enterobacteriaceae (CRE), Clostridium difficile and Norovirus. For proven disinfection of the environmental surfaces in healthcare settings, users turn to Environmental Protection Agency (EPA) registered disinfectants.

All Disinfectants Are Not Created Equal

While healthcare professionals rely on the extensive information provided by EPA-regulated disinfectant products, individual product labels can vary greatly. In the United States and Canada alone, you'll find a plethora of registered disinfectant products for sale, with several notable distinctions. Among the six most common chemistries used for hospital disinfectants, users will find extensive differences in contact times, label language, efficacy, concentrations and personal protection needed for proper usage.

Of these variances, contact time is a common area of confusion for healthcare staff. It is normal to see varying contact times for different micro-organisms with the same use directions. At the same time, products from the same manufacturer may carry different language and instructions for use. Not surprisingly, it can be difficult to decipher the specific language and use directions on one product versus another. As a result of this confusion, proper compliance deteriorates.

Specifically, upon review of the commonly used disinfectant wipes on the market, there are a number of different iterations of use directions in the context of contact time, including:

  • Repeated use of the product may be required to ensure that the surface remains visibly wet.
  • Allow surface to remain wet for x minutes(s).
  • Allow treated surface to remain wet for x minute(s).
  • Allow surface to remain treated for the specific contact time.

The Problem With Wetness

The majority of manufacturers encourage users to ensure a surface remains wet for the duration of the contact time, using additional wipes, if necessary. There are multiple flaws with this approach that contribute to staff confusion and a lack of compliance.

First, there is the practicality of observing wetness, especially if the contact time is fairly long (e.g., 10 minutes). Environmental services teams are expected to work quickly to turnover rooms and typically do not have the time to wait and observe the surface for the stated contact time until, in their opinion, it dries.

That begs another important consideration: "wet" and "dry" are subjective terms, open to individual interpretation. Additionally, temperature, humidity, air flow and the specific surface material all play a role in how quickly a disinfectant (or any liquid) will dry. In fact, the surface may even dry faster than the manufacturer-recommended contact time. Should the environmental services professional then continue to keep the surface wet?

Contact Time? Wet Time

In order to gain an accurate understanding of the meaning behind "contact time," one must examine the manner in which efficacy of disinfectants for hard non-porous surfaces are assessed by the EPA. Most importantly, the EPA does not require test surfaces to remain wet during the test method thus, the concept of "wetness" is irrelevant in measuring contact time.

To demonstrate a specific example, we dissected the method used for evaluating disinfectant wipes: the AOAC Germicidal Spray Test modified for towelettes, although the same principal applies for ready-to-use spray formats.

Test micro-organisms are dried upon a glass surface prior to being treated by the disinfecting wipe in a standardized manner with environmental controls. Following the desired contact time, the glass surfaces are placed in a neutralizing growth medium to inactivate the active ingredient and determine if the test micro-organism(s) have been eradicated. The contact time is determined based on testing by the manufacturer, but must be no more than ten minutes, in accordance with the EPA regulations. During the contact time, the liquid delivered on the glass surface by the wipe is exposed to the air, simulating a typical healthcare environment. As such, the glass surfaces will exhibit varying levels of wetness according to the test conditions.

Specific to Clostridium difficile and Candida auris only, the EPA's interim guidance documents require pre-saturated wipes (towelettes with disinfectants) to provide additional supporting evidence that the surface remains wet for the given contact time. The wetness determination study is in addition to the efficacy study.

In short, environmental professionals should wipe the surface, allow it to be treated and remain undisturbed for the stated contact time (e.g. 2 minutes). As long as the surface is wiped and remains undisturbed (regardless of perceived "wetness" or "dryness"), efficacy can be assured, as this process aligns with the required EPA testing methodology/registration.

Continuing education for staff around these nuanced topics will help equip healthcare professionals with the necessary tools in the quest for optimum compliance and enhanced patient outcomes.

This article was written by James Clayton from Healthcare Purchasing News and was legally licensed through the NewsCred publisher network. Please direct all licensing questions to


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