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Lifx’s bacteria-killing smart bulb works, but here’s the small print

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The LIFX Clean is a smart bulb that can kill bacteria.
The LIFX Clean is a smart bulb that can kill bacteria.
Image: LIFX

The Lifx Clean is a new smart lightbulb with an intriguing twist. Not only is it a fully functional color-changing lightbulb, the company also claims it is capable of disinfecting surfaces and the air around it. First announced last August, the $69.99 Lifx Clean is now shipping to preorder customers in the US, with wide availability planned this spring.

Lifx has an array of scientific studies as well as its own lab tests to support its claim that the Clean is the “world’s first antibacterial, germicidal smart light.” But can the lightbulb work as well in the average home as it did in the lab?

It’s no coincidence that Lifx announced the bulb in a year in which we all had to pay more attention than ever before to keeping ourselves and our homes clean. Lifx’s CEO David McLauchlan says the company started having early discussions about developing a product like the Lifx Clean last March, the same month COVID-19 was officially declared a pandemic by the World Health Organization.

“We saw the alcohol companies were making hand sanitizer and clothing companies were making facial masks”

“We saw the alcohol companies were making hand sanitizer and clothing companies were making facial masks, and I said to the team that we can’t go do these things, but we do make lights,” McLauchlan said in a call. “There’s this technology out there, why don’t we look into it and figure out if we can do this?”

The “technology” McLauchlan is referring to here is a very specific kind of blue light with a wavelength of around 405nm. This high-energy visible (HEV) light has been shown across a number of studies to “inactivate” (read: kill) a range of bacteria including salmonella, E. coli, and methicillin-resistant staphylococcus aureus (aka MRSA) in lab-based studies. 

Other experiments have used it in real-world situations like hospitals. Across three studies conducted between 2010 and 2013, researchers found that the lights reduced the number of bacteria on frequently touched surfaces in a hospital’s burns unit. The reduction varied a lot — between 27 and 90 percent — even within these individual studies, depending on factors like how many days the light was used for, and how much activity there was in the room where it was used.

HEV lights’ lower energy means they’re safe for humans, but also that they take longer to kill bacteria.
HEV lights’ lower energy means they’re safe for humans, but also that they take longer to kill bacteria.
Image: Lifx

The Lifx Clean incorporates this technology into a household lightbulb via an array of eight 405nm LED lights, which sit alongside the standard red, green, and blue diodes that you find in Lifx’s other bulbs. The array then has a typical diffuser placed over it, meaning that it looks almost identical to a standard Lifx bulb.

It’s benign in appearance — vastly different from another light-cleaning tech that’s become popular during the pandemic era: UV light. Pilot programs have used UV light to clean subways, buses, and aircraft cabins, and Transport for London has rolled it out to disinfect escalator handrails

UV is fast acting, but it’s also incredibly dangerous when used incorrectly. That’s according to Jim Malley, a professor of civil and environmental engineering at the University of New Hampshire who’s been studying the use of UV and other light as a disinfectant for over 30 years. It can cause erythema, the reddening of the skin that’s most commonly associated with sunburn, and repeated exposure has even been tied to skin cancer, he says. The light is particularly damaging to your eye’s cornea, and exposure to it can give you “the worst headache you’d ever imagined.” Although your cornea can generally recover from being exposed to UV, Malley tells me, repeated damage “does seem to tie to early blindness.” 

In comparison, HEV light doesn’t have those same problems. “Blue light, 405 nm, doesn’t have that kind of energy,” Malley explains.

HEV light comes with its own disadvantages. Most notably, the light’s effect on bacteria just hasn’t been studied as much as UV. Much of the research that has been done has focused primarily on its ability to kill bacteria, and there’s less evidence to suggest it’s effective against viruses. That’s a very important caveat since COVID-19 is caused by the coronavirus SARS-CoV-2 — a virus.

“I really want to be emphatic that we’re not trying to sell it as a ‘coronavirus killer’”

Lifx isn’t shy about pointing this out. In its announcement for the Lifx Clean last August, the company explicitly said that “no claim is currently being made that the product is effective in an antiviral capacity of any kind, including on SARS-CoV-2.” 

“I really want to be emphatic that we’re not trying to sell it as a ‘coronavirus killer,’” McLauchlan cautions. 

But Lifx still thinks that a disinfecting lightbulb, even if it’s antibacterial rather than antiviral, can help in an era of a global viral pandemic. Bacterial infections, after all, can create serious complications for anyone sick with a virus.

HEV lights aren’t particularly fast when they’re being used to kill bacteria. A study from 2009 found that it took as much as 60 and 90 minutes for 405 nm light to inactivate almost all the bacteria on test, despite the fact that the light was positioned a grand total of 2cm away from it. Hospital studies have focussed on using the light continuously during daylight hours from anywhere between eight to 14 hours or more to achieve their desired bacteria reductions. In comparison, UV light can kill many bacteria and viruses in seconds.

These drawbacks mean that HEV lights haven’t really caught on as a disinfection technology, despite the research backing it up, Malley tells me. 

“It’s not competitive, it’s not practical. You just can’t have hours and hours of contact time” Malley says. In a world where a UV light can sanitize a phone in 60 seconds, 405nm light “can’t compete.”

Lifx provided a report to The Verge of its tests of the light against E. coli and MRSA, which showed how its light performed over periods ranging from two to 12 hours, at a variety of distances. While the Lifx Clean can kill over 80 percent of E. coli bacteria on a glass surface in two hours under the right conditions, you’d have to run Lifx’s Clean bulb for up to eight hours to achieve a similar kill rate for MRSA. 

“It’s not competitive, it’s not practical. You just can’t have hours and hours of contact time”

The length of time involved in killing bacteria is a downside, but McLauchlan argues that the smart bulb’s scheduling features mean you can have it automatically come on when you’re not around. “You can literally have your lights come on at midnight when everyone’s in bed and stay on in the disinfectant mode till 6AM and provide a disinfectant effect in that room or that surface,” McLauchlan says.

The light’s efficacy also declines the farther away it is from a given surface. The results above were achieved by having the bulb just 40 cm away from the bacteria, which puts it at roughly desk lamp height. Move the bulb farther away, and it generally takes longer to kill the same amount of bacteria. Even after eight hours, Lifx’s tests show the bulb only killed around half the MRSA bacteria on a surface four feet away, or just over 65 percent of the E. coli. 

These results mean you’re unlikely to see much of an impact if you expect to use the Lifx Clean as an overhead light. Instead, the company sees people using the bulb in fixtures above desks and other surfaces. To its credit, Lifx is being upfront about these limitations, and these test results are available publicly on its website for everyone to view. If you’re planning on picking up one of the bulbs, it’s worth giving it a read to understand where, and for how long, you’ll need to leave the bulb running to get an effect.

But there are other drawbacks with using HEV light that no amount of smart scheduling or clever placement are likely to be able to overcome. Lifx, for example, initially said the Lifx Clean would be able to disinfect the air surrounding the bulb. However, the slow disinfection time makes that a pretty difficult feat to pull off, Malley explains, because of how air particles tend to move around. 

“They’re not going to be able to keep blue light on that particle of air long enough” Malley says. If bacteria gets really close to the blue light then you could see a reduction, he speculates, “but in general, I don’t think it can compete because you just can’t keep the air near that kill zone long enough.” 

Outwardly, the Lifx Clean looks like the company’s other smart bulbs.
Outwardly, the Lifx Clean looks like the company’s other smart bulbs.
Image: Lifx

There are all sorts of variations in people’s homes that could affect how reliably the bulb kills bacteria. Disinfecting light is, by its very nature, a line-of-sight technology, so any areas of shade won’t be disinfected, and any lampshade in the way will also curtail its effectiveness. One of the hospital studies from 2013 found that the light killed an average of 15 percent less bacteria on the side of a room that was indirectly lit compared to the areas directly under the ceiling lights. It also can’t penetrate deep into porous surfaces, McLauchlan admits. 

The amount of variation in the average home could mean the results Lifx quotes from its lab tests won’t exactly match the real world. For reference, all the test results quoted above had the bacteria sitting on a glass slide. That might work for nonporous surfaces like kitchen or bathroom countertops, but Malley cautions that trying to generalize too much from lab results like this to the average home could end up looking “pretty unrealistic.”

“I wouldn’t see [HEV light] as a substitute for cleaning, but as an adjunct”

Variations like this between lab results and how people actually use products in the home are nothing new, says John Coia, a clinical microbiologist and professor of clinical microbiology at the University of Southern Denmark. Coia co-authored several of the real-world studies that found HEV light could reduce the amount of bacteria when used in hospital settings. He points out that even when it comes to traditional chemical disinfectant, many people might already not be using the correct concentrations. 

“You can make the argument about whether people are using the correct concentration [of HEV light], but do people use disinfectants at the right concentration? The answer is they probably don’t,” Coia says. “In many cases, they probably use concentrations which are actually sub-lethal.” 

Everyone we spoke to, as well as Lifx, agreed that the Lifx Clean isn’t going to replace any normal cleaning. But used correctly, it could be an extra tool in your cleaning arsenal. “I wouldn’t see [HEV light] as a substitute for cleaning, but as an adjunct,” Coia says.

Multiple studies have shown that under the right circumstances, HEV lights like the Lifx Clean certainly can kill bacteria. But even Lifx’s own laboratory tests have shown the limitations of the technology. It needs enough time, it needs to be the right distance away, and it needs a direct line of sight to bacteria in order to kill it. Lifx’s “germicidal smart light” isn’t snake oil, but neither is it a silver bullet that’ll save you from your weekly cleaning chores.