FACE-85-49: Three Fire Fighters Killed Fighting Silo Fire in Ohio
Introduction:
The National Institute for Occupational Safety and Health
(NIOSH), Division of Safety Research (DSR), is currently
conducting the Fatal Accident Circumstances and Epidemiology
(FACE) Project, which is focusing primarily upon selected
electrical-related and confined space-related fatalities. By
scientifically collecting data from a sample of fatal accidents,
it will be possible to identify and rank factors that influence
the risk of fatal injuries for selected employees.
On August 27, 1985, three fire fighters were killed when a
burning silo exploded. The fire fighters were spraying water onto
the fire from the top of the silo at the time of the explosion.
Contacts/Activities:
Officials of the Industrial Commission of Ohio notified DSR
concerning these fatalities and requested technical assistance.
This case has been included in the FACE Project. On September 18,
1985, the DSR research team (a safety engineer, a safety
specialist, and a fire protection engineer) conducted a site
visit, met with the fire chief, officials of the Industrial
Commission of Ohio, and officials of the Sheriff's Department,
and photographed the accident site.
Overview of Employer's Safety Program:
The victims were members of a volunteer fire department. On the
day of the incident, the volunteer fire department had 22 members
on the roster. The fire chief is responsible for training and
periodically conducts training sessions concerning fire fighting
techniques and equipment. The Ohio Fire Service Training Manual
is used as a training resource. No training was received
concerning fires in oxygen-limiting silos.
Synopsis of Events:
On August 27, 1985, the fire department arrived at the scene of
the silo fire at approximately 7:00 p.m. The fire had been
noticed earlier in the day when the owner was "wispy"
smoke coming from the top hatch of the silo. Three fire fighters
climbed to the top of the 76 foot high silo using the access
ladder on the outside of the silo. On top of the silo, they
noticed that one of the hatches was open. After opening a second
hatch on the elevator, they began the application of water onto
the fire using a 1 ½ inch line and a straight stream nozzle. In
approximately 30 minutes 3000 gallons of water (the capacity of
two water tank trucks) were applied to the fire. At this point
the water supply was depleted and the three fire fighters
retreated from the top of the silo.
After a delay of approximately fifteen to twenty minutes, the
water supply was replenished. Three fire fighters once again
positioned themselves at the top of the silo and continued
fighting the fire while two other fire fighters were at ground
level applying water to the bottom hatch area. At approximately
8:00 p.m. an explosion occurred that lifted the concrete roof of
the silo approximately four feet in the air. As the roof began to
break apart in large chunks, victims #1 and #2 fell off of the
silo and victim #3 fell into the silo. A fourth fire fighter at
ground level sustained a broken leg when he was hit by a piece of
the concrete roof. Victim #3, who fell into the silo, was removed
from the silo through a hole that was cut, 28 feet above ground.
All casualties were treated at the scene and transported to local
hospitals. Two different coroners were involved in this accident
due to victims being transported to different hospital districts.
One coroner ruled that victim #1, who fell from the silo roof and
landed on the ground the closest to the silo, died due to
injuries caused by the fall. The other coroner ruled that victim
#2 and #3 died due to injuries caused by the explosion. No
autopsies were performed.
This silo was an oxygen-limiting type which means that the
openings are sealed to limit oxygen from entering. This design
was concrete, slipped-form construction (76' in height, 20' in
diameter) with five rubber gasket sealed hatches (two on the
roof, one at the side loading portal near the top, and two at the
unloading portal at ground level). At the time of the incident,
silage was stored to approximately 12' from the base with silage
extending at a steep angle to approximately 40' up on the sides
of the silo in a cone shape configuration. (After the explosion,
the silage collapsed to the 28' level.) The initial indication of
cause of ignition was spontaneous heating of the silage.
Witnesses state that the bottom and the top doors of the silo
were open when the fire department arrived. This would allow
sufficient oxygen for spontaneous heating to occur and the silage
was sufficiently dry for this action to take place.
The explosion was due to either a build up of combustible gases
from incomplete combustion or a dust explosion, or a combination
of the two. In either case, directing water into the top of the
silo would have been an improper method for fighting this type of
silo fire. In this incident, nothing should have been done to
increase the level of oxygen inside the silo. Both opening the
top hatches to apply water to the fire and entrained air within
the water stream increased the level of oxygen and put the gases
and/or dust into the explosive range. Additionally, water spray
can place the dust into suspension, thereby increasing the risk
of explosion.
Cause of Death:
The cause of death for victims #2 and #3 was due to
"injuries caused by explosion" and for victim #1,
"injuries caused by fall from silo."
Recommendations/Discussion
Recommendation #1: During fire fighting operations, water
should not be directed onto the fire through the top hatches of
an oxygen-limiting silo.
Discussion: A fire in an oxygen-limiting silo can be
potentially very hazardous since explosive gases can be
contained. Any increase in oxygen may place the gases into their
explosive range. One method of fighting this type of fire that
has met with success in the past involves the injection of liquid
nitrogen or carbon dioxide into the silo to extinguish the fire.
Manufacturers of the silos normally have instructions on putting
out fires in their silos. Further information can be obtained
from the bulletin: "Extinguishing Silo Fires" which is
published by the Northeast Regional Agricultural Engineering
Service, NIOSH Alert: "Request for Assistance in Preventing
Hazards in the Use of Water Spray (FOG) Streams to Prevent or
Control Ignition of Flammable Atmospheres," No. 85-112, and
the NIOSH report: Occupational Safety in Grain Elevators and
Feed Mills, No. 83-126.
Recommendation #2: When not being filled or emptied,
the silo hatches should be kept closed, and proper maintenance on
the silo should be performed to ensure the integrity of the
oxygen-limiting features.
Discussion: If an oxygen limiting silo is properly sealed,
there is very little likelihood of a fire occurring by
spontaneous heating since there is usually insufficient oxygen to
support a fire. The manufacturer of the silo should be contacted
for proper operating and maintenance procedures for the silo.
Additionally, further information on minimizing the possibility
of a silo fire can be obtained from the bulletin,
"Extinguishing Silo Fires," referenced in
Recommendation #1.
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