NFPA Journal - March/April 2018 - 61

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.
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

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
p Under UL's new standards, smoke alarms
lot of research had to go into
will need to differentiate between burning
figuring all of that out."
polyurethane foam (top) and burning burgers.
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.
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. -J.R.
N F PA . O R G / J O U R N A L * NFPA JOURNAL

| 61

http://WWW.NFPA.ORG/JOURNAL

Table of Contents for the Digital Edition of NFPA Journal - March/April 2018