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

Sign Here

A primer on the development of smoke signature technology—the basis of new-generation smoke alarms


DEVELOPING THE UNDERLYING knowledge and technology needed for a smoke alarm to discern between burning furniture and a burning burger was a long process shaped by industry, UL, NFPA, and others.

"To make this work, you have to understand all of these underlying principles about smoke before you can develop the underlying tests to develop the equipment," said Barry Chase, an engineer at NFPA who works on smoke detection. "How do I know what smoke looks like? How do I know what kinds of smoke to ignore and not to ignore? A lot of research had to go into figuring all of that out."

The first step was learning what the products of combustion, or smoke, look like for various burning substances. Smoke isn't just dirty air, and it isn't uniform; it's a swirl of gases and particles with different sizes, densities, compositions, concentrations, compounds, and even colors, depending on what's burning. Smoke generated by a burning hamburger has a different set of characteristics than say, a burning duvet cover. While researchers inherently understood this, as recently as 10 years ago no adequate analysis had ever been done to figure out what those differences look like.

Testing of burning polyurethane foam


Hamburgers cooking in a oven

Under UL's new standards, smoke alarms will need to differentiate between buring polyurethane foam (top) and burning burgers. Photographs: UL

In 2007, UL partnered with the Fire Protection Research Foundation on a smoke characterization study to shed light on these questions. Relying on smoke particle and gas effluent characterization technology that had never been available before, researchers documented for the first time the smoke characteristics of a variety of modern home materials and products. By 2010, between the FPRF study and a subsequent UL study, researchers had characterized 60 smoke signatures from various burning household objects.

"Those projects were that catalystic 'a-ha' moment in the scientific world," Guthrie said. "Until you know what to detect, you cannot get more sophisticated in your detection. After, it's kind of like reverse engineering—now we have what the smoke is, how do we make sure alarms react to it or don't react?"

As smoke signatures became better understood, advancements in computer technology and big-data algorithms were developed that enabled alarms to quickly read what smoke they were seeing, then make rapid calculations about whether or not it posed a threat. Meanwhile, UL worked to create and validate the complex testing standards needed to ensure that the next generation of smoke alarms would perform as promised.

JESSE ROMAN is associate editor for NFPA Journal.