C a r l N i x W hen was the last time you responded to a hazmat call? Arriving on the scene often forces firefighters to make decisions based on what they don’t see. Bring in a thermal imaging cam- era (TIC) and firefighters can see what was previously
invisible to the naked eye. This allows the firefighting
crew to make better and safer decisions on the scene.
A TIC can be an invaluable tool for the hazmat
firefighter. Having the ability to see the content level
of an enclosed container at a safe distance is critical to
the safety of the firefighting crew. Tracing a spill on the
roadway in a rain storm is an environmental necessity.
Seeing the gases of a container at a safe distance is critical to the safe outcome of a hazmat mission.
While a TIC cannot remove the hazardous materials
at an incident, it can help firefighters locate and isolate
the materials. Let’s look at how a TIC can help a
firefighting crew at a hazmat incident.
We have all responded to a scene where a vehicle was
overturned and wondered if there were any materials
leaking from that vehicle. Using a TIC in this situation
allows the firefighter to detect the differences in temperature or emissivity (level of reflectivity) between the
vehicle, its contents, and the ground surface around the
incident. If the spilled material is a different temperature
than the surface on which it is spilled and the material
stays on the surface, it should be visible on the TIC.
If the product has already drained from its container
prior to fire department arrival, a TIC can be used to
identify the location of the contents that have leaked
onto the surface. Be aware that there are factors that
may influence how well a TIC will work in this situation, including the amount of product leaking or
spilled, properties of the material, denseness of the vegetation where the spill has occurred, and the relative
temperature difference between the spilled material
and the surrounding environment.
Using a TIC to identify a hazmat floating on a body
of water can help firefighters identify where the material is entering the water supply and how much of the
water supply has been contaminated. The differences
in emissivity or temperature of the contaminant will
allow the firefighter to see a visible difference on the
TIC screen. It is important to note that only materials
that weigh less than water can be identified using the
TIC. A TIC cannot see through water.
Materials in contact with the surface of a container
can conduct heat through the walls of the container
at a slower rate than the dead air space above the
product. Unless the product was heated prior to being
placed in the container, its level will be identified by a
darker image (indicating cooler temperature) on the
lower part of the container wall. The dead air space or
vapor area will usually show as lighter on the screen of
the TIC. If the container is insulated, it will not show
the temperature difference.
To determine if a container is full or empty, use
the TIC to scan other containers in the area to look
for variations in color. The difference in color of the
container may be attributed to a difference in material
construction. When viewing containers or piping,
remember that shiny surfaces can reflect heat from the
surrounding area and give erroneous readings of the
actual surface temperatures. The firefighter reading
the TIC may be seeing a reflection of the heat of something in the background.
When firefighters are called to the scene of a gas
leak, they can often smell the gas or feel it escaping
under pressure, and they are often forced to employ gas
detection equipment to find the point of origin. A TIC
gives responders an additional tool to tackle this job.
Most leaking gases will have a different heat signature
than that of the surrounding atmosphere, allowing the
TIC to identify the vapor cloud. Numerous factors will
influence this capability, including the concentration or
density of the gas, the temperature of the vapor in relation to the surrounding atmosphere, and whether the
gas is transparent or opaque to infrared radiation.
When a gas escapes from a cylinder or pipe, it cools
the immediate point of origin unless the gas is at an
elevated temperature. The TIC sees the point of origin
as darker than the rest of the picture unless variations
in the environment prevent this, such as atmospheric
variations including sub-freezing temperatures or man-made conditions such as heating.
Fortunately, hazmat incidents are not frequent, but
they are challenging. The TIC increases safety and
helps to provide more accurate information so the
incident commander can make better decisions.
Carl Nix is a 32-year veteran of the fire service and a retired battalion chief of the Grapevine (TX) Fire Department. He serves as an
adjunct instructor for North Central Texas College and a thermal
imaging instructor for Bullard. Nix has a bachelor of science degree
in fire administration and is a guest instructor for Texas A&M Engineering Extension Service’s (TEEX) annual fire training in Texas.
Responding to a Hazmat Call
Using a TIC to detect spills and leaks