Understanding Disinfectant Dwell Times
In order to kill pathogenic micro-organisms (illness-causing bacteria, fungi, viruses) in the workplace, disinfection dwell times and efficacy claims (what the disinfectant is proven to kill) are extremely important.
Dwell time is the amount of time the surface you are disinfecting must remain visibly wet with the product before it’s wiped off. A common problem is that many products require a dwell time upwards of 10 minutes to reach their full kill-claim, and surfaces often get wiped off prematurely. Clearly, dwell time is a major factor that can impact the efficacy of the disinfection process.
There are many different disinfectant formulations that vary primarily based on chemical composition, efficacy claims, and dilution ratios. Common types of disinfectants used for commercial facilities may include active ingredients like quaternary ammonium (quat), sodium hypochlorite (bleach), hydrogen peroxide, silver ions, iodine, acids, or alcohol, each of which may be effective on different strains of pathogens.
Some types of disinfectants are more effective against viruses while others are more effective against bacteria commonly found in and around food preparation areas. Products with claims for control of microorganisms that pose a threat to human health require specific efficacy data to support such claims and patterns of use.
Dwell times can vary by disinfectant and target organism type (bacteria, virus, or fungi), and while a disinfectant may kill some of the organisms immediately upon contact, the product must be allowed to dwell on the surface for the full amount of time stated on the product label. While you may have the necessary cleaning and disinfecting supplies, it’s essential that you use proper cleaning and disinfecting techniques.
Paired with proper training, this can go a long way toward ensuring that surfaces in your facility are effectively disinfected. It’s essential that your staff know the appropriate amount of time the disinfectant must remain wet on the surface before wiping it off. What may seem like a relatively small step can make all the difference for the health and safety of your employees and anyone entering your facility.
Levels of Disinfection Efficacy
There are three different levels of disinfection: high, intermediate, and low. High-level disinfection is capable of killing all organisms, except high levels of bacterial spores, and is effected with a chemical germicide. Intermediate level agent destroys all vegetative bacteria, including tubercle bacilli, lipid and some nonlipid viruses, and fungi, but not bacterial spores. These agents are registered as “tuberculocide” by the US Environmental Protection Agency (EPA). A low-level disinfectant has no tuberculocidal claim and kills some viruses and bacteria with a chemical germicide registered as a hospital disinfectant by the EPA.
The CDC states that mycobacterium tuberculosis has one of the highest levels of resistance of all microorganisms. Therefore it is used to measure how well a product can kill other germs of lower resistance. If a disinfectant has a tuberculocidal claim, it is considered capable of killing a broad spectrum of pathogens or having a “broad-spectrum kill claim.”
“Kills 99.9% of Germs*” – Read The Fine Print
Some of the most widely used disinfectants that are sold in the U.S. are effective on only a small number of pathogens. Yet many of these products are marketed with the claim “kills 99.9% of germs.” That’s why it’s important to read the fine print that lists the microorganisms the product actually kills, as it may or may not include some or all influenza viruses. A good rule of thumb to follow is that if you see an asterisk* on a label, the product’s marketing claim that it “Kills 99.9% of Germs” needs closer examination.
Here are a few examples of a label marketing claim versus label reality:
“Kills 99. 9% of germs* – Product may kill only a small amount of different strains or types of germs, sometimes as few as 3 to 4 pathogens.
“Kills in 30 Seconds* – Not every organism claimed on the label is killed in 30 seconds, making the claim especially misleading. Typically, it’s only 1 or 2 organisms that are killed in 30 seconds. The remainder of germs claimed actually take a full 5 or 10 minutes of dwell time.
By law, disinfectants must list the microorganisms the product has been tested for and found to be effective against on their label, as well as proper directions for use, including dwell times. You should always check the product label for the specific pathogens you are disinfecting for.
Disinfectants kill only select strains of germs and no disinfectant is capable of killing all germs found on a hard surface. The absence of all germs is referred to as sterilization and is a process that surpasses the efficacy level achieved with any disinfectant solution. EPA-registered chemical sterilants are the only types of sanitation products that can make a claim to kill all pathogens on hard surfaces.
No Single Disinfectant Will Work for Every Application and in Every Setting
It’s a common misconception that “bleach kills everything,” which isn’t actually true. Although bleach is effective against some bacterial spores, bleach-based solutions generally do not have as wide of a range of efficacy against the types of pathogens that a high-level quaternary ammonium disinfectant solution may have. The bottom line is that no single disinfectant solution will work for every application and in every setting.
For concerns about cold or flu, you would want to choose a product with a wide range of claims against viruses or with a broad-spectrum kill claim. In healthcare settings, antibiotic-resistant bacteria and Clostridium difficile (C.diff) are present.
Often hospitals and other healthcare facilities will use more than one disinfectant solution to effectively combat the different types of pathogens they are most concerned with. Schools and daycare centers may have specific organisms of concern, such as RSV, whereas animal care facilities need products with efficacy claims specifically for animals, such as canine parvovirus or feline leukemia.
Antimicrobial Products For Use Against Sars-Cov-2
In March of this year, the EPA released a list of antimicrobial products for use against SARS-CoV-2, under an emerging viral pathogens program. Under the program, introduced in 2016 and activated for the first time in January, makers of disinfectants can request approval to claim a product that is expected to kill a particular virus based on its ability to kill similar viruses.
Once an outbreak has been identified and the identity of the virus is confirmed by the CDC, approved products are temporarily permitted to distribute information about using the product for the emerging pathogen. The emerging pathogens program sidesteps the lengthy review process that is typically required for vetting disinfectant efficacy claims, which requires the establishment of a standardized protocol and testing with the actual virus or an EPA-approved surrogate.
According to the CDC, SARS-CoV-2 is believed to spread primarily person-to-person through airborne respiratory droplets. But it may also be possible for the virus to spread on surfaces as well. Although scientists aren’t exactly sure yet how long the novel coronavirus remains active on a surface, one study done in a hospital found that similar coronaviruses can persist on hard surfaces like glass, metal, or plastic for up to 9 days. Another study, recently published on medRxiv and not yet peer-reviewed, found that SARS-CoV-2 remains stable on plastic and stainless steel for 2–3 days.
Before deciding on which disinfectant is right for your specific purpose, be sure to read its label for efficacy claims, and follow the instructions for the proper amount of dwell time needed for the product to reach its full kill claim potential.
Why You Should Clean And Disinfect Your Facility
Commercial cleaning and disinfection services for facilities large and small include offices, medical, retail, industrial, multi-tenant high-rises, and all commercial spaces in between. They can customize a cleaning and disinfection plan specific to your facility’s needs while minimizing downtime to your operations.
Cleaning technicians use a combination of hand wiping and an electrostatic sprayer – an effective tool in supplementing the everyday janitorial cleaning methods used in offices and commercial facilities.
Electrostatic spraying kills viruses, including SARS-CoV-2 which is the virus that causes COVID-19. It has been proven to kill 99.99% of viruses in a matter of minutes, making it not only effective but also extremely fast-acting.
How much dwell time is needed to kill the COVID-19 virus?
Some products are more effective at killing certain germs than others, and different pathogens may require different dwell times. If you’re not sure how long your disinfectant needs to kill the coronavirus, consult the EPA’s website. Here are some recommended dwell times for common cleaning products:
- Lysol Disinfectant Spray: 3 min.
- Sani-Cloth AF3 Germicidal Disposable Wipes: 3 min.
- Clorox Germicidal Wipes: 1 min.
- Oxivir TB Disinfectant Cleaner Wipes: 1 min.
- Clorox Healthcare Fuzion Cleaner Disinfectant: 1 min.
- Lysol All Purpose Cleaner with Bleach: 30 sec.
- Lysol Mold and Mildew Remover with Bleach: 30 sec.
- Clorox Hydrogen Peroxide Disinfectant Wipes: 1 min.
- Clorox Broad Spectrum Quaternary Disinfectant Cleaner: 3 min.
Dwell times are an important part of the cleaning equation, but they’re not the only factor. Keeping your facility properly disinfected and coronavirus-free takes expertise.
Does a shorter dwell time mean a product is more effective?
When comparing dwell times, keep in mind that they don’t necessarily indicate a product’s effectiveness. They simply tell you how long it takes for the product to work. A disinfectant with a 10-minute dwell time can be just as effective as one that works in only seconds—as long as you leave it on for the full 10 minutes. When choosing cleaning products for your facility, dwell time is just one of the factors to consider.
How do I ensure the dwell time is reached?
The most common mistake people make when using disinfectants is applying the product and immediately wiping it off. To meet the dwell time, the disinfectant needs to remain wet upon the surface for the entire duration. Since cleaning products often dry within minutes—especially if they contain alcohol—you may need to keep reapplying it until the dwell time is reached. “In normal HVAC settings, water can evaporate anywhere between six-and-a-half to eight minutes,” says Patrick Kehoe, cleaning chemicals marketer for 3M. “Thus, keeping a surface wet for 10 minutes could require a heavier initial application or the need to rewet the surface.”