1
24-040
Explosion-Proof Enclosure Failure to Contain a Lithium-Ion
Battery Thermal Runaway
Thomas H. Dubaniewicz
CDC NIOSH, Pittsburgh PA
ABSTRACT
Gassy underground mines commonly use explosion-proof
(XP) enclosures to enclose electrical ignition sources to
prevent propagation of an internal methane-air explosion
to a surrounding explosive atmosphere. Researchers at the
National Institute for Occupational Safety and Health
(NIOSH) conducted a lithium-ion battery thermal run-
away test within a modified MSHA-approved XP enclosure
to assess thermal runaway containment. Thermal runaway
produced jet flames emanating from the cover joint at sev-
eral locations and distorted the cover joint and bottom
plate of the enclosure beyond allowable limits. The test
demonstrates that XP enclosures may not provide adequate
explosion protection against lithium-ion battery thermal
runaway. This paper suggests some approaches to mitigate
the hazard.
INTRODUCTION
Lithium-ion (Li-ion) battery fires are becoming more com-
monplace in the United States. Fire departments across the
country held a week-long safety stand-down during June
2023 themed “Lithium-Ion Batteries: Are You Ready?”
[1]. Large-format Li-ion powered battery electric vehicles
(BEVs) are in the early stages of deployment in underground
mines in the United States. GlobalData [2] reported a total
of 10 active electric Load Haul Dump (LHD) vehicles and
trucks in U.S. underground mines as of March 2022. A
Li-ion BEV fire at an underground operation in Nevada
prompted a U.S. Mine Safety and Health Administration
(MSHA) order to suspend operations to protect the mine
workers at the operation [3]. The Nevada incident repre-
sents a failure rate of well into the percent range for fires
per deployed Li-ion battery LHDs and trucks in U.S.
underground mines. Several Li-ion battery truck fires have
occurred in Canadian underground mines as well [4, 5],
representing a failure rate in the percent range for a larger
sample size of 76 electric LHDs and trucks [2]. All of these
incidents involved heating from short circuits external to
the battery or external to multiple cells within a large bat-
tery rather than a single-cell internal short circuit.
Li-ion BEVs in gassy underground mines pose unique
explosion hazards. Dubaniewicz et al. [6, 7] reviewed the
gassy mine explosion hazard and the use of explosion-proof
(XP) or flame-proof enclosures for explosion protection of
electrical equipment. Mines commonly use XP or flame-
proof enclosures in potentially explosive atmospheres to
enclose electrical ignition sources to prevent propagation of
an internal methane-air explosion to a surrounding meth-
ane and coal-dust-contaminated atmosphere. Emergencies
involving ventilation disruption may produce explosive
atmospheres. Stranded battery energy is one potential
ignition hazard after mine power is shut off during such
24-040
Explosion-Proof Enclosure Failure to Contain a Lithium-Ion
Battery Thermal Runaway
Thomas H. Dubaniewicz
CDC NIOSH, Pittsburgh PA
ABSTRACT
Gassy underground mines commonly use explosion-proof
(XP) enclosures to enclose electrical ignition sources to
prevent propagation of an internal methane-air explosion
to a surrounding explosive atmosphere. Researchers at the
National Institute for Occupational Safety and Health
(NIOSH) conducted a lithium-ion battery thermal run-
away test within a modified MSHA-approved XP enclosure
to assess thermal runaway containment. Thermal runaway
produced jet flames emanating from the cover joint at sev-
eral locations and distorted the cover joint and bottom
plate of the enclosure beyond allowable limits. The test
demonstrates that XP enclosures may not provide adequate
explosion protection against lithium-ion battery thermal
runaway. This paper suggests some approaches to mitigate
the hazard.
INTRODUCTION
Lithium-ion (Li-ion) battery fires are becoming more com-
monplace in the United States. Fire departments across the
country held a week-long safety stand-down during June
2023 themed “Lithium-Ion Batteries: Are You Ready?”
[1]. Large-format Li-ion powered battery electric vehicles
(BEVs) are in the early stages of deployment in underground
mines in the United States. GlobalData [2] reported a total
of 10 active electric Load Haul Dump (LHD) vehicles and
trucks in U.S. underground mines as of March 2022. A
Li-ion BEV fire at an underground operation in Nevada
prompted a U.S. Mine Safety and Health Administration
(MSHA) order to suspend operations to protect the mine
workers at the operation [3]. The Nevada incident repre-
sents a failure rate of well into the percent range for fires
per deployed Li-ion battery LHDs and trucks in U.S.
underground mines. Several Li-ion battery truck fires have
occurred in Canadian underground mines as well [4, 5],
representing a failure rate in the percent range for a larger
sample size of 76 electric LHDs and trucks [2]. All of these
incidents involved heating from short circuits external to
the battery or external to multiple cells within a large bat-
tery rather than a single-cell internal short circuit.
Li-ion BEVs in gassy underground mines pose unique
explosion hazards. Dubaniewicz et al. [6, 7] reviewed the
gassy mine explosion hazard and the use of explosion-proof
(XP) or flame-proof enclosures for explosion protection of
electrical equipment. Mines commonly use XP or flame-
proof enclosures in potentially explosive atmospheres to
enclose electrical ignition sources to prevent propagation of
an internal methane-air explosion to a surrounding meth-
ane and coal-dust-contaminated atmosphere. Emergencies
involving ventilation disruption may produce explosive
atmospheres. Stranded battery energy is one potential
ignition hazard after mine power is shut off during such