Division of State Fire
Marshal
Bureau of Forensic Fire and Explosives
Analysis
Q: What is an accelerant?
A: An accelerant is technically anything which speeds up a process. In arson, most
accelerants are ignitable liquids. The most common ignitable liquid used as an accelerant
is gasoline.
Q: How do you find ignitable
liquids?
A: Fire scene investigators utilize their skills and tools (electronic sniffers and
specially trained canines) in the fire scene to find areas with a high
probability of the presence of an ignitable liquid. They collect one or more samples
and place them in vapor tight containers. These are sent to the laboratory.
The technicians and analysts in the Bureau subject the evidence to a
technique called "passive headspace concentration" in order to extract trapped
ignitable liquid molecules, put into a liquid solution. The solution (extract) is then injected
into a gas chromatograph with mass spectral detector. This instrument creates an
electronic representation of the
organic chemicals in the sample mixture. The complexity of this mixture is
represented as a "total ion chromatogram" which can then be further
subdivided into specific ion fragment profiles and mass spectra to determine the presence or
absence of characteristics specific to ignitable liquids.
Q: What if somebody mixes several
ignitable liquids together?
A: Ignitable liquids can be divided into several classes based on the presence or
absence of specific chemical compounds. Familiarity with these classes allows the analyst
to distinguish between a medium petroleum distillate and deteriorated gasoline. If a
mixture were used the analyst should see a mixed pattern and should be able to make a
differentiation.
Q: How should evidence from a
fire scene be preserved and packaged?
A: Evidence from fire scenes should be packaged so that the sample is protected
from both evaporation of volatile residues or contamination of the residues after
they are collected. This is best accomplished by placing the sample in an
air-tight container. The most common are clean unused paint cans with a friction lid which is tightly sealed. Glass jars with tight fitting
screw-on lids (using a Teflon type liner) may also be used. If glass jars are used, take care that they will not break
during transport or shipment. Some brands of nylon "arson" plastic evidence bags are on the market. Some
studies show them to be very useful so long as they are sealed properly. BFFEA
strongly suggests limiting their use to items with odd shapes or bulk that
will not fit into a gallon paint can. If the debris placed inside them has sharp points or
edges, the plastic bag could be punctured. Plastic bags must be completely
heat sealed. Regardless of the type of container used, place the
debris in it without drying as this will reduce the presence of the ignitable liquid
traces. The container should never be filled more than fifty (50%) to
seventy-five (75%) percent full,
as the laboratory needs an adequate vapor space above the debris for testing.
Please see the "Guidelines for Submission" on the Bureau Main Page.
Q: What are the key exceptions or
differences if I have evidence from explosions or clandestine labs?
A: The Bureau will not accept any intact explosive devises. They must be
rendered "safe", or disassembled before submission. For items from a clandestine
laboratory, if there is a suspicion that any drugs are present, the item must be
submitted to the Florida Department of Law Enforcement (FDLE) as the Bureau will
not accept any drugs for analysis. Items other than fire debris or organic based
solvents should not be directly placed into a metal container as the item may
chemically react with the metal. Instead, glass or plastic containers should be
used. Be careful to observe if there is a chemical reaction or gas evolution
inside the container as this may cause a build-up of pressure in the container
to the point where it would burst. Additionally, these types of evidence may
require larger sampling amounts to ensure an adequate variety of tests. Please
call the Bureau if in doubt.
Q: What can I (the investigator) do to make sure the best sample
is sent to the lab?
A: First, take care in selecting the sample to be tested. It is best to take a
sample from the area of origin between the center and the edge of a pattern
suspected of containing an ignitable liquid. Second, send the sample to
the laboratory as soon as possible. Deterioration of ignitable liquids occurs
whenever they are not sealed in air-tight containers. Additionally, certain microbes have been known to "eat"
components of ignitable liquids. If the concentration of ignitable liquid is
low and the presence of microbes high (as in soil samples), a delay in sending the sample
may cause enough of a change in an ignitable liquid so that the analyst cannot make a
clear determination. Third, if at all possible, send in a "comparison" sample.
This would be a sample (preferably un-burned) of the same type of material as in the
debris to be tested. For example, if the sample from the point of origin is burned carpet
and padding, a sample of the same type of carpet and padding from a protected area (under
a bookcase or planter) would be a good "comparison sample." The laboratory will
burn the "comparison" sample under controlled conditions so that the potential
interferences can be seen. Comparison samples are also any absorbents
used to collect a sample. A paper towel, gauze pad, or hydrophobic pad used
to absorb a liquid should be tested to determine it is was contaminated.
This test is done by submitting an unused portion of the absorbent material
as a separate comparison sample. Comparison samples of any absorbents used
to collect a sample should be taken at a different location as ignitable
liquid vapors may be absorbed from the air near the scene.
Q: How long will it take to get results?
A: Ninety-five percent of the samples submitted to the Bureau are completed and a report
issued in fewer than 10 calendar days. Certain cases, depending on the number of samples
and the difficulty in interpreting the results, can be completed in two to three days.
These RUSH cases need to meet certain criteria:
1. Fatality - If a fatality occurred in the
incident it should
have rush priority.
2. Injured victims or responders. If there are burn victims or first
responders who were
injured in any phase of the incident (fire suppression, scene investigation, or
scene clean-up)
it should be marked as rush.
3. Major fires or explosions with significant dollar losses. If a city block, a large business, or
historical site should burn or be involved with an explosion it should be
marked rush.
4. Suspect in custody/impending court would also be a rush criteria.
Q: Who can submit samples?
A: At this time, the Division of State Fire Marshal's Bureau of Forensic Fire
and Explosives Analysis
will accept samples from any government/public service agency in Florida. This includes
all police or fire investigation agencies for the state, county, or municipality.
This, also, includes investigators from State's Attorney Offices or from the
Public Defender's Offices. Other State of Florida or federal agencies
investigating incidents occurring in Florida may submit evidence, but should
contact the Bureau in advance. In the spirit of forensic cooperation,
foreign law enforcement or fire investigation agencies have been permitted
to submit evidence under specific instances and with prior approval.
Q: What does an analysis of the
evidence cost the submitting agency?
A: At present, the only cost to the submitting agency is the cost of
shipping the evidence to the laboratory. The Bureau does not charge for analysis of samples.
We do charge reasonable and customary fees for the reproduction of reports,
case files, and photographs/images. Foreign submitters must also agree to
bear all shipping costs to and from the Bureau as well as any costs
associated with bringing Bureau personnel to their courts for testimony.
Q: Who do I contact if I need further information?
A: Call Bureau Chief Carl Chasteen at 850/539-2700 or e-mail
Carl
Chasteen.
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