NFPA Journal - Fall 2021 - 44

Guidance
needed
in the container, leading to even more accumulation of
unburned gases, the APS report concluded.
By comparison, NFPA 855 requires energy storage systems
to follow NFPA 68, Standard on Explosion Protection by
Deflagration Venting, or NFPA 69, Standard of Explosion
Prevention Systems-either of which " would have potentially
changed the outcome here, " McKinnon said. But he also says
that the venting requirements in NFPA 855 for lithium-ion
batteries specifically could be strengthened. That's especially
true now that further research and details from the Surprise
incident have revealed the enormous amount of flammable
gas produced during thermal runaway in lithium-ion cells.
Jim Biggins, the chair of the NFPA 855 technical committee,
agrees. " We're looking at providing additional guidance
in NFPA 855 both for explosion venting and normal venting
of the battery enclosures and battery rooms, " he said. " It's
such a large volume of gas coming out of a single cell during
thermal runaway, and I don't think anybody fully understood
that mechanism previously. "
The other areas that observers hope NFPA 855 might
address may be tougher nuts to crack. All parties agree that
real-time remote gas monitoring that would help firefighters
understand the composition and makeup of gases produced
during thermal runaway would make a significant difference.
However, there is uncertainty about how to achieve it. The
current edition of NFPA 855 is mostly silent regarding off-gas
monitoring because " the technology really wasn't there to a
point where we felt comfortable making it a requirement in
the standard, " Biggins said.
Multiple technical challenges, such as the heavy soot
produced from thermal runaway, high heat, stratification of
gases, and a mixing of gases has the potential to overwhelm
and destroy gas sensors inside the unit, which " make it a
very complicated problem, " McKinnon said. " Because of
those challenges, there are no products or solutions I am
aware of that can do this. "
At least one company claims to have real-time gas monitoring
and boasts that its technology can even catch atmospheric
HOW MUCH PROTECTION IS ENOUGH?
Hard to say, since the results of fire testing of energy storage systems aren't
widely shared. But efforts are underway to remedy this.
OR YEARS, battery manufacturers
have been
diligent in testing their own
products to see how they
perform in fire situations and
what hazards they present,
according to Jim Biggins,
chair of the NFPA 855 technical
committee. But most of
that information is considered
proprietary and is siloed away,
which makes it difficult for the
committee to draft adequate
guidance, he said.
" That was a huge problem
when we were writing
NFPA 855, because not all
F
lithium-ion batteries are
created the same, " Biggins
said. " There are different
chemical compositions, they
have different characteristics,
and they're going to perform
much differently [during
fires]...there's no one-size-fitsall
for protection guidance. "
Biggins referred to research
conducted recently by the
Fire Protection Research Foundation
(FPRF) and FM Global
that demonstrated that two
similar lithium-ion batteries
can give off very different
amounts of energy during fire
Researchers burn a lithium-ion ESS at the
UL Large Scale Fire Test Facility in Illinois.
tests. On top of that, even
the way the batteries are
configured in a rack-whether
they're stacked vertically or
horizontally-can have a significant
impact on a fire, the
spread of thermal runaway,
and the level of protection
required.
Because of these challenges,
NFPA 855 contains
few specific protection
requirements. Instead, the
standard " pushes hard for
individual system fire testing,
so these companies will know
more about their technology,
more about what
gases come off
during thermal
runaway, more
about what protection
will work
with their specific
chemistries
and battery configurations, "
said
Brian O'Connor,
who was the
NFPA 855 staff
liaison when the
standard was
developed. The
problem with
this approach is
that the majority
of battery
testing now
being done is
44 | NFPA JOURNAL * FALL 2021
for specific installations, and
results are rarely shared in the
interest of furthering safety
for everyone.
But there are indications
that could be changing. This
summer, the FPRF sent out
invitations to various stakeholders
to join what it calls the
Energy Storage Research Consortium.
The idea is to bring
together researchers, manufacturers,
and a host of others
to perform tests and share
data and results that can be
publicly disseminated so that
standards like NFPA 855 can
have a better foundation on
which to build their safety
recommendations.
" If that happens, the NFPA
855 committee can be a little
more specific in some of the
protection requirements than
we are right now, " Biggins
said. " If you look at what was
done with, say, warehousing
storage, you're able to make
assumptions based upon
the storage classifications
about how much sprinkler
density you're going to need
to protect it. The idea is that
hopefully we can classify the
batteries in the same sort of
way in different groupings
for protection. Hopefully the
research can get to that point.
I think we will get there. " -J.R.
COURTESY OF UL FIRE SAFETY RESEARCH INSTITUTE
NFPA Journal - Fall 2021

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