Author(s): Jesse Roman. Published on March 1, 2018.

Smoke Signals

Smart smoke alarms that can distinguish between burning food and burning furniture will hit the market this spring. How it happened, and why safety advocates call it “a game changer.”


In his day job as staff liaison to NFPA 72®, National Fire Alarm and Signaling Code®, Richard Roux spends more time than most trying to dissuade people from disabling their smoke alarms. But he understands the impulse.

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Even Roux has moments of temptation, especially when he uses the stove in the small kitchenette of his family's RV. "The smoke alarm is guaranteed to go off every single time," he says, blaming the cramped quarters that prevent him from placing the device at least 20 feet from the stove, as NFPA 72 advises for homes.

For people who have experienced this frustration, which is to say nearly everyone, there may be good news. Breakthroughs in research and technology have brought us to a point where the next generation of smoke alarms will be able to discern between smoke from routine cooking and smoke generated by a serious fire. In fact, alarms will soon be mandated to detect this kind of difference.

Beginning in 2020, UL, one of the world's largest developers of safety standards for consumer products, will no longer list smoke alarms that are unable to pass a series of tests designed to prove they are resistant to cooking and other sources of false alarms. In other words, every new smoke alarm that enters the market by 2020 should be largely free of the problem of activating because someone forgot about the dinner rolls warming in the oven. It is perhaps the most significant change of the 250 technical changes UL made to the most recent editions of the standards it uses to certify and list smoke detection devices.

A technician at UL's new smoke alarm testing facility loads alarms into a movable arm that will lower them into a testing room.

A technician at UL's new smoke alarm testing facility loads alarms into a movable arm that will lower them into a testing room below. Photograph: UL

"This is a life safety game changer," said Barb Guthrie, public safety officer at UL. "What we are now able to place in people's homes is a smart device that can recognize all of these atmospheric conditions around the smoke alarm and sound faster with a degree of accuracy that we never had before."

The significance extends well beyond solving a longtime annoyance—it also has important ramifications for life safety. Even though few faux pas in the fire and life safety world are as maligned as messing with a smoke alarm, plenty of people continue to do so, sometimes with tragic consequences. NFPA statistics show that the majority of the roughly 2,700 people who die annually in residential fires in the United States live in homes with no smoke alarms or no working smoke alarms. Many of the alarms, studies have found, didn't work because they were disabled by residents annoyed by their squawking and were never put back in working order.

Nuisance alarms have also taken their toll on fire departments. In 2014, U.S. fire departments responded to almost 2.5 million false alarms, about twice the total number of reported fires and five times the number of structure fires, according to an NFPA analysis. Most were triggered by commercial monitored connections, including residential buildings such as apartment buildings, hotels, and dormitories.


The issue of what to do about this problem has confounded safety advocates for decades, whose lone hope seemed to rest in convincing people not to tamper with their alarms. The more permanent solution—to make better and more discerning alarms—has for years been technologically impossible. Building an alarm that will sound only during a real fire and not from a burning piece of toast is simple in concept but maddeningly complex in practice.

For as long as smoke alarms have existed, they have been yes or no devices: Either they detect enough smoke to sound an alarm, or they don't. That's true for alarms using photoelectric or ionization detection, the two prevailing technologies on the market today. To cut down on nuisance alarms, the new breed of smoke alarm will have to determine what kind of smoke it is sensing. Not only must it have the capability to measure precisely the composition of smoke particles to decipher what's burning, it must then make a judgment about whether that thing is a threat or not.

That represents a sea change for the industry, according to Roux. "I don't think there is an alarm on the market today that can do this," he told me in February.

That may no longer be true. Days after speaking to Roux, Guthrie told me that UL was in the process of testing the first batch of new detectors to the new standard and expects them to be on the market sometime this spring. That does not mean, however, that residents, inspectors, or code officials need to take any action to replace still-functioning older alarms, Guthrie stressed. Those alarms still work just fine, and do not need to be replaced—that will happen organically over time through attrition, she said.

Testing of the new-generation alarms is occurring now at a new lab UL opened in February on its campus just north of Chicago. The facility is dedicated to smoke detection research and to testing their capabilities against the revised UL standards. Inside is an 800-square-foot testing room that is sealed airtight with the help of a submarine door to keep atmospheric conditions as sterile as possible to ensure controlled, consistent, and repeatable measurements. Lab technicians load alarms into a moveable ceiling in a room above the test site, then lower them to precise heights above the smoking test substances.

Flame jets out of a cylinder that has been filled with balled newspaper as part of a paper fire test

A cylinder filled with balled newspapers is ignited as part of a paper fire test, one of the five tests smoke alarms must pass. Photograph: UL

So far, tests on the new products have been promising. In a recent nationally televised demonstration of the new-era alarms, UL technicians placed a baking sheet with hamburgers under the broiler; within 10 minutes, the traditional alarms sounded, while the new models sat silently even as smoke levels increased. While the burgers continued to burn, in the same room UL technicians then lit a small slab of polyurethane foam, the quick-burning substance used as cushioning in most modern furniture throughout the world. In less than three minutes, the new alarms sounded as the foam burned, signaling an important new threat.

This quick reaction to synthetic polyurethane foams was another important addition to the new UL smoke detection standards. The additional test helps ensure that alarms will sound within three minutes of a fire, giving residents crucial time to escape, Guthrie said. Studies have shown that modern construction and synthetic furnishings have led to fires that can burn significantly faster than in years past, reducing evacuation time from an average of 17 minutes to less than four, according to UL. NFPA's public educators advise that, in modern home fires, residents could have less than two minutes to get out safety once the smoke alarm sounds.


Despite—or perhaps because of—these changes sweeping over the industry, manufacturers and industry professionals have largely remained tight lipped about their new products, the technology involved, and how the new listing criteria might impact the industry or the costs borne by consumers. When contacted, a representative from one large detector manufacturer declined to comment or say even when the new alarms might come to market, citing "confidential" and "proprietary" concerns.

What is clear is that much work is now underway to prepare for the approaching 2020 deadline to meet UL's new standard. Since the new UL detection facility opened, demand from manufacturers has been robust, according to UL, which has run extra shifts to accommodate the companies eager to test their devices to the new requirements.

"Are there devices right now that will pass? Well, they have to go through the test," Guthrie said, when asked about early results. "In the majority of cases there might be some tweaking done, of course, because this nuisance aspect of (the testing) is extremely new."

Even so, manufacturers have been preparing for some time. While UL first published the new product standards to little fanfare in October 2015, manufacturers, code developers, and industry professionals anticipated, and in some cases pushed for, the standards even years before that. The technology, research, development, and code making has moved in lockstep (see "Sign Here," previous page).

NFPA 72 first included language referencing smoke alarms "listed for resistance to common nuisance sources from cooking" in the 2013 edition, even though no such listing existed at the time. The section stated that smoke alarms listed for resistance to cooking could be positioned as close as six feet from a stationary cooking appliance, or stove-regular alarms still have to be located at least 20 feet from a stove to reduce the possibility of nuisance cooking alarms, according to the code.

The language alluding to devices resistant to nuisance alarms was added after several public inputs were submitted by stakeholders seemingly with the aim of nudging more sophisticated testing standards.

Thomas Hammerberg, then president of the Automatic Fire Alarm Association, wrote in a public input to the NFPA 72 technical committee at the time that, although the committee "has done a great job using research to craft smoke detector location/placement/spacing requirements that can effectively reduce nuisance alarms, the rules in NFPA 72 for household smoke alarms are not adopted by all jurisdictions and, even if they are, they are not always effectively enforced. The problems of nuisance alarms can be addressed across the board by implementing more rigorous testing standards."

Hammerberg, who has since retired from leading the association, declined to comment on the new UL standards.

Other than fulfilling the NFPA 72 committee's premonition from 2013, the UL testing and listing changes should not have any impact on NFPA 72 itself, Roux said.

"Listing is certainly important, but it's only one of the criteria that smoke alarms must meet," Roux said. "Installation, wiring, and location are also among the requirements spelled out in NFPA 72."

In terms of real-world impact on the industry and consumer safety, though, it's hard to overstate how significant the UL listing changes will be, Roux said. For one, he may soon be able to cook a burger in his RV without fear of what the alarm will do.

"The result will be significantly greater immunity from cooking, resulting in fewer unwanted alarms," he said. "This is a win/win for the consumer and for safety."

JESSE ROMAN is associate editor for NFPA Journal. Top Photograph: Thinkstock