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Bureau of Forensic Services

Frequently Asked Questions

Q: What is an accelerant?
A: An accelerant is technically anything which speeds up a process. In deliberately set fires, most accelerants are ignitable liquids. The most common ignitable liquid used as an accelerant is gasoline. The BFS determines the presence and identity of ignitable liquids. Whether or not they were used as "accelerants" is for the investigator or the courts to determine.

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. We encourage, but cannot require, that comparison samples be collected and sent as well. Comparison samples are typically building materials of the same type as the samples submitted for analysis which the investigator believes are not contaminated with any ignitable liquid. These may be from a separate unburned area of the structure or may be a sample of a material used to adsorb or absorb liquids from puddles or containers. As each fire is unique, there may not be an area or item which the investigator is confident of being a proper comparison sample.

The analysts in the Bureau subject the evidence to a technique called "passive headspace concentration" in order to extract trapped ignitable liquid molecules. After being extracted from the evidence sample, the trapped ignitable liquid molecules are put into a liquid solution of carbon disulfide. 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.

The laboratory reports ignitable liquids using the classifications recommended by the American Society for Testing and Materials (ASTM) in their standard test method E1618. The table Ignitable Liquid Classifications describes the various classifications and provides examples of the classes. The following table shows the identity of ignitable liquids determined by BFS since 1992:

Findings 1992 to 2017
Samples
Percent
No ignitable liquid/Negative
45,152
56.25%
Gasoline & Gasoline Mixtures
27,507
32.08%
Petroleum Distillates & Petroleum Distillate Mixtures
4,901
5.14%
Oxygenates
921
0.90%
Isoparaffinic Products
271
0.35%
Naphthenic/Paraffinic Products
257
0.28%
Aromatic Products
410
0.51%
Normal Alkane Products
153
0.20%
Miscellaneous
3,989
3.29%
Inconclusive
9
0.32%
Total
83,570



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 of two or more significantly different ignitable liquid classes were used the analyst would see a mixed pattern and may 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 or polyamide "arson" plastic evidence bags are on the market. Some studies show them to be very useful so long as they are sealed properly. BFS strongly suggests limiting their use to items with odd shapes or bulk that will not fit into a gallon 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 link to "Guidelines for Submission" on the Bureau Main Page. Please note that unlike other State of Florida Crime Laboratories, BFS has a rule under the Florida Administrative Code that describes the requirements for submitting evidence to the Bureau as well as the requirements for the return of the evidence (FAC 69D-5.001).

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 of fire debris from the suspected area(s) 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 and mold covered building materials), 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 prepare 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 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 8 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 (during the fire, 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 Investigative and Forensic Services Bureau of Forensic Services 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 may be 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 costs for work performed by the Bureau as well as any costs associated with bringing Bureau personnel to their courts for testimony.

Q: Where can I learn more about the schools that offer degrees in forensics?
A: The following websites list several of the schools and information although there are additional resources if you search the web:

http://aafs.org/students/colleges-universities
http://www.ncjrs.gov/pdffiles1/nij/203099.pdf
http://forensicsciencetechnician.net

Q: Who do I contact if I need further information?
A: Call Bureau Chief Carl Chasteen at (850) 539-2705 or via e-mail