Published ASHI GLC Laker, Winter 2012:
Ionization versus Photoelectric Smoke Alarms:
In
Real-World Fires The
Differences Are Deadly
By
Skip Walker, ACI, MCI
Imagine
your car air bags deploying randomly when you hit a
pothole, but failing over half the time in a
collision. As unthinkable as this seems, that is the
harsh reality with the smoke alarms found in most US
and Canadian homes. Like most, I always assumed that
a smoke alarm was a smoke alarm. What I now know is
that there are two basic types of smoke alarms;
Ionization and Photoelectric. In real-world fatal
fires, these alarms behave very differently. In this
case – different is not good. Knowing the difference
could very well save your life.
“A
smoke detector that sounds approximately nineteen
minutes after smoke reached its sensing chamber is
like an airbag that does not deploy until nineteen
minutes after a car accident.”
-Judge
David E. Schoenthaler, Mercer v. Pitway/BRK Brands
(First Alert)
Over 90% of US homes have ionization
smoke alarms installed, around 5% of have
photoelectric alarms installed and the rest have no
alarm of any kind. In the mid-70's about 10% of US
homes had at least one smoke alarm installed. Now
about 96% of US homes have at least one smoke alarm.
Yet after installing smoke alarms in over 100
million US homes, the risk of dying in a fire has
remained roughly the same. Maybe it’s just me, but
that doesn't make sense.
Between 1977-2009, the number of home
fire deaths decreased about 56%. During the same
period, the number of home fires declined similarly
for a decrease of about 50%. However,
the fire death rate per thousand
fluctuated considerably up and down between 6.5 and
10 deaths per 1,000 fires. The overall fire death
risk remained essentially the same over the period –
7 to 8 deaths per 1000 fires. What impact did
installing hundreds of millions of ionization alarms
actually have?
When
the death rate per 1,000 home fire incidents is
looked at, there is no steady decline, but rather
the rate fluctuates considerably..... These results
suggest that even though the number of home fires
and home fire deaths declined similarly
during the
period, the death rate did not, and when there is a
home fire,
the fire death rate risk has not changed
much for the period.
Source: NFPA Fire Loss
2009 / Pg 7-8
The
smoke alarm industry is quick to point out that all
smoke alarms must meet the UL 217 and UL 268
standards developed by Underwriters Lab (UL) to be
installed in US homes. Canadian alarms have somewhat
different UL-Canada (ULC) standard. The major alarm
manufacturers, UL, National Fire Protection
Association (NFPA), Consumer Product Safety
Commission (CPSC) and National Institute for
Standards and Testing (NIST) have long maintained
that any UL listed alarm afford adequate protection
in most fires. More recently, they have begun to
recommend that we have both types of alarms. This
position infers that all fires carry equal risk of
death. However, the fire statistics and studies published by
these same organizations do not support that
position. In fact, decades of research and data shows just the
opposite.
Current
UL alarm standards are essentially the same as those
developed in the 1970's. The UL 217 standard defines
the requirements for alarm response. The UL tests
use two test scenarios. One is a “fast flame” fire,
the other is for smoldering fires. A “fast flame”
fire is a fire that is based on accelerants, such as
gasoline, cooking oils, grease, and paper fire. A
smoldering fire is the early stages before open
flames develop and is characterized as slow moving
with significant smoke. The smoldering fire tests
standards were developed when most home furnishings
were natural materials, cotton, wool, etc. Today,
virtually all furnishings and a large percentage of
the building materials are synthetic and engineered
materials. The behavior of natural and synthetic
materials in a fire is radically different. Yet the
UL standards have not been adjusted to account for
this shift.
In
tests, ionization alarms will typically respond
about 30 to 90 seconds faster to “fast-flame” fires
than photoelectric smoke alarms. However, in
smoldering fires ionization alarms respond an
average of 15 to 50 minutes slower than
photoelectric alarms. Several studies indicate that
they will outright fail to activate up to 20-25% of
the time. The vast majority of residential fire
fatalities are due to smoke inhalation, not from the
actual flames and almost two-thirds of fire
fatalities occur at night while we sleep.
In
1995, researchers at Texas A&M University published
the results is a 2 1/2 year study on residential
fire detection devices. The research showed that
ionization alarms failed to provide adequate egress
time in smoldering fire scenarios over 55% of the
time versus a 4% failure rate with photoelectric
alarms. In fast-flame fire scenarios, the study
found that ionization alarms failed to provide
adequate egress time about 20% of the time versus 4%
with photoelectric alarms. The research demonstrates
that when all factors are taken into account, i.e.;
how often each alarm gets disabled due to nuisance
tripping, how they respond across the full spectrum
of fires, etc., photoelectric alarms have a clear
advantage.
In
2007, UL published the “Smoke Characterization
Study”. This study tested both types of smoke alarms
using current UL testing standards and materials;
they also tested the alarms using UL test criteria
integrating a variety of synthetic materials and
current tests such as smoldering toast. The results
are frightening. Ionization alarms failed the UL 217
test 20% of the time using the current standard test
materials. This is the test that the alarms must
pass 100% of the time to be offered for sale and
installed in US homes. When tested using synthetic
materials, ionization alarms DID NOT TRIGGER (DNT)
in 7 out of 8 synthetic test scenarios. In the one
test where the ionization alarm did trigger, it
activated at a level exceeding maximum allowed under
the UL standard and nearly 43 minutes after the
photoelectric alarm in the same test.
In the
same tests, photoelectric alarms activated 100% of
the time using the UL 217 test and materials. When
tested using the standard test integrated
synthetic materials, photoelectric alarms responded
properly in 100% of the tests. Overall, the
ionization alarm outperformed the photoelectric in
only one scenario, the “burnt toast” test, where it
responded 22% faster. There were 3 test scenarios
where neither alarm activated. The UL researchers
determined that the sample size used was too small
to generate sufficient smoke. Those materials were
re-tested using larger samples. The results of those
tests are shown in the above test scenarios.
Ionization alarms are also notorious for nuisance
tripping, i.e.; going off when you cook, burn toast,
shower, etc. When alarms nuisance trip, people
become frustrated and intentionally disable the
alarms. This leaves the family completely
unprotected. According to several studies,
ionization alarms are 8 times more likely to be
intentionally disabled. Ionization alarms account
for the vast majority of disabled alarms. Several
CPSC and NFPA studies indicate that ionization
alarms account for 97% of all nuisance alarm
activations. An Alaskan Public Housing Study shows
that about 20% of ionization alarms will be disabled
within the first year of installation; other studies
indicate that this percentage may be higher.
Remember, about 96% of US homes have at least one
smoke alarm. Yet 2/3's of all residential fire
deaths occur in homes that are have either no alarm
or no functional alarm. That implies that most
people die in fires because they either do not
maintain their alarms or they intentionally disable
them. To complete the picture, many of the remaining
1/3 of residential fire deaths occur in homes where
an alarm sounds, but it sounds too late for the
occupants to escape.
“Nationally,
the percentage of people dying when the smoke
detector works, but works too late, is approximately
40 percent,”
-Jay Fleming, Boston Deputy
Fire Chief, CBS Boston Interview, 2007
After
decades, there is finally a growing awareness of
this issue. On October 3, 2012, the
NBC Today Show and NBC Nightly News aired a “Rossen
Report” investigative segment on this issue. On
July 7, 2012 with a follow-up report on
August 1, 2012, Huntsville, AL TV station WHNT
aired “A Taking Action” investigative report
featuring ASHI Vice President Bill Loden. On
November 16, 2012,
CBS 5 San Francisco aired a ConsumerWatch segment
featuring retired Albany Fire Chief Marc McGinn and
myself.
The
International Association of Firefighters (IAFF) is
the largest firefighters union in the US and Canada
with nearly 300,000 members. In 2008, the IAFF
adopted an official position recommending that only
photoelectric smoke alarms be installed. The IAFF
position also commits the organization to working
for changes in the law and model codes to require
photoelectric technology alarms. Further, the IAFF
position specifically states that combination type
alarms are not acceptable. In July, 2010, the City
of Albany, California became the first city in
California to require photoelectric smoke alarms in
new construction and remodels. Followed in late 2010
by Palo Alto, CA and Orange, CA that enacted
ordinances requiring photoelectric technology
alarms. In January 2011, the City of Sebastopol, CA
enacted an ordinance requiring photoelectric
technology. A number of cities in Ohio have enacted
similar ordinances. The North Eastern Ohio Fire
Chiefs organization has a very strong photoelectric
only position.
In
2011, the California Real Estate Inspection
Association (CREIA) became the first home inspection
organization in the world to take a stand when CREIA
adopted a position mirroring the IAFF position. At
this time, Vermont, Massachusetts, Maine and Iowa
have laws on the books that require photoelectric
technology smoke alarms in residential construction.
Similar action is under consideration in several
states and in New York City. The Northern Territory
in Australia recently adopted a photoelectric
technology law.
Which type of technology do I have?
It is
not always possible to know. In general, if the
label says anything about radioactive material,
Americium-241 or the model number has an “I,” - then
it is almost certainly an ionization alarm. If you
have any doubt, there is over a 90% chance that the
alarm that you have is an ionization unit. To be
safe, simply replace any unknown units with
photoelectric-only alarms. Any smoke alarm that is
10 years or older should be replaced as well,
regardless of type.
What
about Combination Alarms?
There
are combination photoelectric/ionization smoke
alarms available. In fact, many fire officials
mistakenly recommend them. There is no industry or
UL standard for dual/multi sensor alarms. As long as
they respond to the UL 217 and 268 tests, the
manufacturers are free to alter the way the sensors
respond and interact with each other. These units
have the same issues as ionization only detectors.
In some cases – they may be worse. A CPSC study
shows that they may be even more prone to nuisance
tripping than ionization alarms when in close
proximity to cooking sources.
In the
simplest terms, if you take a device that works and
pair it with a device that has serious shortcomings
– how can that possibly improve performance? Both
the International Association of Fire Fighters (IAFF)
and CREIA specifically recommend against installing
combination alarms. NIST
is on record stating,
”Since an individual sensor can be set to meet all
current sensitivity standards, it is not obvious
what overall benefit is achieved from a dual
alarm...”
Combination alarms use technology termed “Gated
Logic”. In one type, either sensor tripping will
sound the alarm. In these units, the photo portion
will pick up the smoldering fires so the ionization
sensor does not become a factor. However, the ion
portion is still susceptible to nuisance tripping.
The manufacturers do not want the customer to
disable the alarm. So to combat nuisance tripping,
they often reduce (desensitize) the smoke
sensitivity/response of ionization portion of these
units. In effect, this type of combination alarm
performs similarly to a photoelectric only alarm.
With
the other type of unit, BOTH sensors must trigger to
sound the alarm. In these units, the photoelectric
portion will pick up the smoldering fires first, but
will not sound until the ionization sensor triggers.
Since a smoldering fire usually pose the greatest
danger, this is a problem. The family is often fast
asleep while the alarm waits for the ionization
sensor that may never respond or responds too slow.
This type alarm needs both sensors to detect the
danger or it won’t alert. Conversely, while this
unit will be less susceptible to nuisance tripping
because the photoelectric sensor must also respond
to nuisance sources such as burnt toast; you risk
losing your life if the ionization doesn’t respond
in a dangerous smoldering fire situation.
No
single alarm can save everyone in every possible
circumstance. There are many promising technologies
being developed. With everything we know, all the
facts tell us that photoelectric alarms provide
superior protection in real-world fatal fires. They
are affordable and available today. Do not allow
your family, friends, neighbors and clients to
become yet another statistic. This year, don't just
replace your smoke alarm batteries – replace your
alarms with photoelectric alarms and recommend that
everyone you know do the same!
About the author:
Skip Walker lives in the SF Bay Area and has
performed over 3,500 property inspections since
2003. Skip is an ASHI Certified Inspector (ACI), a
Master CREIA Inspector (MCI), an ICC Certified
Residential Combination Building Inspector and an
F.I.R.E. Certified Inspector. Skip is the past
education chair for the Silicon Valley ASHI/CREIA
Chapter, CREIA 2010-2011 State Secretary and the
CREIA Region Three Director 2009-Current. Skip has
spoken on smoke alarm safety issues at various ASHI
and CREIA meetings. He has represented the home
inspection profession at the California Association
of Realtors (CAR) 2009-2012 and the National
Association of Realtors (NAR), 2011. Skip's home has
ONLY photoelectric alarms installed. You may reach
Skip at (650) 873-4224 or by email at:
HomeInspection@sanbrunocable.com. |