Part two of this three-part article examines new disinfectants with shorter dwell times.

As some building service contractors call into question the standard 10-minute dwell time, companies are bringing to market a host of new products with kill clams as short as 30 to 60 seconds.

“Nowadays people have learned that the contact time is really important,” says Tanner. “If you don’t use the whole contact time you don’t get the full benefit of the disinfectant. So the market is now pushing really hard toward shorter contact times for disinfection. And I do think they confer a much better infection control benefit than a traditional dilutable quaternary ammonium disinfectant with a 10-minute contact time.”

In general, quaternary ammonium disinfectants have slower contact times and are the most commonly used disinfectants, says Tanner, who likens them to “a soap that kills germs.” They typically kill bacteria in 10 minutes, but they cannot kill C. diff, which is the most difficult bacterium to kill. Today, there are about 35 EPA-registered quat formulations that can kill non-enveloped viruses, such as norovirus and rotavirus.

In comparison, some of the newer products on the market have a kill claim of four minutes for C. diff and one minute for norovirus. The easiest microorganisms to kill are enveloped viruses, such as influenza and HIV-1, which some of the newer disinfectants can kill in 60 seconds. 

Concentrated bleach products and accelerated hydrogen peroxide products have the fastest kill claims, says Tanner.

“The amount of contact time will vary based on the disinfectant,” he adds. “For example, if you have a potent disinfectant, C. diff might take fives minutes to kill, and bacteria might take 30 seconds. If it’s a weaker disinfectant, C. diff might take 10 minutes, and bacteria might take two minutes. As a rule of thumb, it takes three to five times longer to disinfect C. diff then it does to disinfect bacteria.”

At Pristine Environments in San Diego, janitors use a hydrogen peroxide-based disinfectant in charter schools to disinfect surfaces in restrooms, classrooms and gymnasiums. The product is used for general-purpose disinfecting, says Naser Gjeloshi, Eastern region senior vice president of operations, and janitors adhere to standard disinfection times. The product has a kill claim of one minute for HIV-1 and H1N1 and 10 minutes for MRSA, Influenza, Staph and Salmonella.

“If a school was to call about a MRSA outbreak, we would use a disinfectant specifically for MRSA with a shorter kill time,” says Gjeloshi. But for routine cleaning practices, he is cautious about over-disinfecting. “A 10-minute dwell time is not a problem for us,” he says. “Most cleaning companies want employees to rush, and the dwell time is sometimes overlooked. We make sure each individual has enough time to properly disinfect the restroom.”

Despite the availability of newer disinfectants with shorter kill claims, some building service contractors, like Gjeloshi, continue to use standard dwell times. But Hicks calls into question the ongoing efficacy of any disinfectant beyond the first 60 seconds.

“Science doesn’t prove that keeping the surface wet for 10 minutes improves infection prevention,” says Hicks. “According to U.S. Centers for Disease Control and Prevention (CDC) … if [a surface] stays wet for a minute or greater then it doesn’t matter which disinfectant you use — a three-minute or a 10-minute one. There are multiple scientific studies that demonstrate disinfectants all reach their peak in the first 60 seconds.”

When disinfecting, paying attention to proper techniques is just as important as contact time.

“Studies show that on discharge [from a hospital], 50 percent of the surfaces were never touched or adequately decontaminated because the worker missed them totally,” says Hicks. “So I think it’s more important that we get more than 50 percent of the surfaces disinfected than dwelling on dwell times.”

No doubt the dwell time debate will continue — as will building service contractors’ commitment to educating janitors about the importance of disinfection and training them in proper disinfection procedures.

“It’s not just about telling people to follow dwell times,” says Griffin. “You have to give them the rationale and training so that they understand why dwell time is important and what happens if they don’t allow for the proper dwell time: It’s a risk to themselves and the public. If they see the value of adhering to the dwell time, there’s a better chance they will follow those procedures.”

previous page of this article:
The New Standard In Dwell Times
next page of this article:
Should Cleaners Spray Disinfectants Onto Surfaces?