Cory Chalmers’s cleaning team looks a lot like Stormtroopers out for a raid.
“We’ve got the white Tyvek suits, the full-face respirators,” Chalmer tells Popular Mechanics. And, of course, the pièce de résistance: electrostatic guns loaded with sodium troclosene, a disinfectant that, when dissolved in water, creates a fine mist of chlorine gas. The guns give the sodium troclosene particles a static charge that makes them cling to objects. When Chalmers and his gang of Galactic Empire cleaners want to disinfect something, all they have to do is point and shoot.
Chalmers, the president of biohazard and crime scene cleanup company Steri-Clean, Inc., has been busy this spring. In the wake of the COVID-19 (coronavirus) pandemic, practically every indoor space in the country—schools, businesses, entertainment facilities, airports, government offices—has closed so sanitizing services like Steri-Clean can “deep clean” to kill the virus, which is transferred via respiratory droplets expelled when someone with the disease coughs, sneezes, or talks, and lives on surfaces for up to three days.
Wearing two layers of gloves (the outer set is thicker, the inner set is taped to sleeves), the Steri-Clean team members spray an initial disinfectant on all surfaces and “touch points,” or everywhere you put your hands. That means door handles, light switches, keyboards, the backs and arms of chairs, plus all horizontal surfaces, like tables, countertops, desks.
“[We] touch probably 30 to 40 percent of a room,” Chalmers says. After the first wipedown, the cleaners toss their towels in biohazard bags and ship them off to a medical waste facility for incineration.
Then comes round two: disinfecting. Using spray bottles, the electrostatic guns, and—depending on the size of the job—full-room sanitizing misters, the cleaners soak everything down. Once it’s dry, they use test strips to measure adenosine triphosphate, or ATP, a molecule found in living cells that tells them how many microorganisms are present on a surface. A typical high-touch surface, such as a refrigerator handle, will have an ATP reading close to 2,000 before it’s cleaned, Chalmers says. Lower than 20 is “food grade,” and he aims to get as close to zero as possible.
Only when the numbers are acceptably low do the cleaners then strip off their protective suits and call it a day.
Of course, that’s just the way Chalmers and his crew do it. Because despite what you might think, there aren’t any universal rules for what constitutes a “deep cleaning.” In fact, the phrase doesn’t actually mean anything at all.
“Other types of cleaning do have established standards,” Chalmers says. The Occupational Safety and Health Administration (OSHA) governs bloodborne pathogen and biohazard cleanup, and requires employees at companies doing that work to have specialized personal protection equipment training. But when it comes to the kind of “deep cleaning” prescribed to battle a pandemic like COVID-19, “there’s really no one overseeing that,” says Chalmers. “People ask us what agency we send the [ATP] reporting to, and the answer is nowhere. There’s no such thing.”
Still, the phrase alone seems to bring people comfort, especially in light of a study from The New England Journal of Medicine that found COVID-19 can persist on cardboard for up to 24 hours, on plastic and steel for 72 hours, and even on copper, with its natural antimicrobial properties, for 4 hours.
“Early on, schools and universities announced they were going to close during spring break and do a ‘deep cleaning,’” says Annette C. Reboli, M.D., an epidemiologist and dean of the Cooper Medical School of Rowan University in New Jersey.
“Really, I think that was largely about allaying the fears of students and parents,” she tells Popular Mechanics. “All surfaces everywhere have microorganisms on them; it’s impossible to eliminate them permanently, or even for a long period of time.”
But that hasn’t stopped the mad dash to deep clean—and that’s a good thing. Because while “right now there hasn’t been a documented transmission of the COVID-19 virus from a surface to a person,” Reboli says, “it’s a matter of time.”
Inactivating the Virus
Coronaviruses get their name from their shape; they’re round molecules studded with protein spikes. (In Latin, corona means “crown” or “wreath.”) When the virus infects a host—usually animals like pigs, camels, or bats, but occasionally there’s human spillover—the spikes help the viral particles attach to receptors on healthy cells.
The protein spikes of COVID-19 protrude from the molecule’s surface, a double layer of lipid (fat) cells that hold everything together. Without an intact lipid bilayer, the molecule breaks apart. It’s not technically correct to say it dies, because it’s not technically correct to say viruses are alive in the first place. But once that layer comes apart, the virus is rendered inactive, unable to infect host cells even if it does enter the body.
The classic ways to inactivate the virus include targeting that membrane, Warner Greene, M.D., Ph.D., a virologist at the Bay Area research lab Gladstone Institutes, tells Popular Mechanics. Disinfectants that use a form of chlorine, such as household bleach solutions, work by breaking apart the lipids and “unfolding” the proteins. Similarly, ethanol-based disinfectants work by extracting the lipids from the membrane, causing the proteins to break apart. Other cleaning products use a detergent that solubilizes (dissolves or absorbs) the lipids.
Heat and UV light also work by basically boiling or scalding the lipid bilayer beginning at about 130 degrees Fahrenheit. While a human fever won’t reach nearly high enough to get the job done, you can effectively sanitize infected clothing in about 45 minutes in your average dryer.
A heated dry cycle in your dishwasher can also be helpful for sanitizing metal and plastic items—just be sure they’re either marked dishwasher safe, or made of a material that won’t melt.
“The net effect is you’re breaking the bilayer, either by scrambling it or extracting it,” Greene says. But time is also a factor. “None of those processes happen in a nanosecond. In general, you have to thoroughly wet a surface and let it dry in order to destroy the virus that may be on it.” Killing the COVID-19 virus can take between 30 seconds and 10 minutes of “contact time,” depending on the cleaning product you use.
Not everything is capable of inactivating this type of virus, but this, at least, is regulated. The Environmental Protection Agency (EPA) reviews antimicrobial pesticides, including disinfectants. If they’re effective, the EPA adds them to a document called List N and gives them an official registration number. There are a number of common household cleaning products on the list, including Windex Disinfectant Cleaner, Comet Disinfectant Cleaner, Fantastik Multi-Surface Disinfectant, and a number of Lysol and Clorox products.
“Products can qualify for inclusion in List N if they meet either of two criteria,” EPA spokeswoman Andrea Drinkard tells Popular Mechanics. “The product qualified for an Emerging Viral Pathogens claim by demonstrating efficacy against a harder-to-kill virus than [COVID-19], or the product demonstrated efficacy against another human coronavirus similar to [COVID-19].”
Still, even the “EPA does not have standards for ‘deep cleaning,’” Drinkard says. And assuming you don’t plan to have a cleaning crew come through your home daily, the best way to get your space sanitized is to use the right products—and use them properly. Wiping things down with Lysol wipes alone won’t suffice; while those are on List N, they have a contact time of about 10 minutes. That means you need to spray, wipe, and let it soak.
Take stock of the “touch points” in your home and clean them regularly. Every time you touch doorknobs, handles, and chair backs, for example, you reinfect them with whatever microbes are on your hands. Remember to sanitize them several times a day.
'The Scope Is Unimaginable'
The world of biohazard and crime scene cleanup is a relatively small one, Chalmers says, but it may well be one of the only industries experiencing growth in the midst of mass quarantines and closures.
“Everyone in this industry is getting calls from every company, either contracting us to come out and clean, or trying to come up with contingency plans,” says Chalmers. “As the number of infected people continues to rise, and they trace where these people have been, they’re wanting to get all those places clean. There’s usually not a big demand to clean up death and biohazard, but they say [COVID-19] is expected to affect half the country—maybe more. That’s half of all the buildings and homes that all need to be cleaned. The scope is unimaginable.”
The situation is unprecedented, and Chalmers says he’s having to figure out how to clean places he never anticipated he might be called to.
“We did a pharmacy the other day,” he says. “You can imagine, with all the rules around controlled substances, how many people needed to be there and the hoops we had to jump through. A dam operator tested positive, so we had to clean the dam. We’re wondering things we’ve never had to wonder, like, ‘Can we spray disinfectant on a dam’s control panel?’” (Yes, Chalmers adds. They can.)
Steri-Clean has more than three dozen offices across the country, but a hastily growing client list requires hiring more employees, and Chalmers worries he won’t be able to properly equip them. A shortage of personal protection equipment like face masks has impacted hospitals around the country. At the moment, cleaning crews have many of the same concerns.
“We don’t want to keep blowing through our supplies,” Chalmers says. “We are really asking the general public to stop buying things like respirator masks if they don’t need them. I can’t find full-face respirators anywhere right now, and my supplier says they’re two or three months out. I got desperate, and ordered three masks on eBay. One showed up; the other two were ‘lost in transit.’”
Store shelves have been empty of disinfectants for weeks, and Chalmers worries about his supply. “We were supposed to get 14 cases of disinfectant last week,” he says, “and not a single bottle was on the truck when it arrived.”
Much of the deep cleaning happening in spaces that people continue to frequent is ultimately a bit futile, Chalmers admits. COVID-19 “will come back as people start touching things again,” he says. “Once we leave, whatever people do, whatever diseases or viruses they bring back into that space, we can’t control. We can just hope we made some kind of difference, and they’re taking precautions.”
And yet, we have to keep cleaning, says Greene.
“Sticking to plastic and stainless steel is just another way [the virus] could transmit, and the fact that it can persist on these surfaces is not good,” he says. “I do not think this is a highly efficient mechanism of transmission, but it’s one I take precautions against. You could stay six feet away from everyone in the world, and touch the wrong door knob. It’s a small, but manageable risk.”
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