Disinfecting the kitchen counter or the bathtub? Just spray on some Lysol or bleach—and boom done, right? Not so fast. When it comes to disinfection, the “contact time” is a critical component.
Compounds that disinfect—like alcohol, bleach, and other disinfectants—all kill X biological substances on a surface over Y amount of time. The amount of time it takes to kill off microorganisms to the degree that the surface or material is considered sanitized or disinfected per standards organizations like the EPA publish is called “contact time.”
The majority of people concerned with contact time are people working in restaurants, food production facilities, hospitals, nursing homes, and other places where tight control over pathogens is critical. People cleaning their homes should be aware of it, too.
If you’re trying to sanitize your house after a nasty bout of food poisoning or a tenacious skin infection (like your kids brought ringworm home from summer camp), understanding the contact time for the disinfectant you’re using is critical. How do you know how long to leave it on the surface? When in doubt, as long as the product doesn’t indicate it needs to be removed, you can let it completely dry in place. If the product is labeled as disinfecting, however, it should also list the contact time. The contact time is a critical part of the claims you see on products like “Kill 99.9% of fungi, viruses, and bacteria.*” The asterisk always points to the fine print that says. “When used as directed.”
If you’re not following the contact time rules for the cleaner you’re using, you cannot be sure you’re actually sanitizing or disinfecting the surface.
For example, if you read the label on the back of the nearly ubiquitous Lysol disinfecting spray or check out the company’s web site, you’ll note they don’t use the term “contact time,” but they do expressly state how long you should leave it on:
Surfaces must remain wet for 3 minutes then allow to air dry. For Norovirus surfaces must remain wet for 10 minutes then allow to air dry.
Those kind of instructions aren’t a suggestion. They’re specifying under what conditions their product is considered sanitizing or disinfecting per EPA/CDC guidelines to meet the “99.9%” similar claim on the container.
So the next time you’re on a cleaning bender, focused on ridding your home of the last stubborn traces of the illness that took your family out of a commission for a week (or just trying to prevent an illness from doing so), make sure you check the instructions on the cleaner you’re using and leave the cleaner in place for the suggested duration.