Chemistry Reference
In-Depth Information
allowed to proceed and extinguished by a fire fighter. As can be seen, much
soot (C
(s)
from incomplete combustion) has been deposited on the walls
during the fire.
Less damage appears to have been caused to the sofa at the front of the
image. This is in keeping with the knowledge that the fire was started by
throwing a petrol-soaked rag through the right-hand side window. As you
will see, extensive damage has been caused to the bed coverings, pillow and
the covering of the base of the bed (in comparison to the bed on the left-hand
side of the image). A scene investigator would use a combination of postfire
indicators, evidence from fire and rescue employees who attended the scene,
information from other witnesses and data obtained from laboratory analy-
ses to form a conclusion on what he or she thinks has occurred. he science
of fire behaviour (fire dynamics) is a complex, although well documented,
subject but exceeds the scope of this topic; see the Further Reading section
for more specialised texts on this subject.
8.4.5 Sample Preparation
Debris collected from a fire scene is usually collected in a metal tin, nylon
bag (Figure 8.29a) or glass jars. These items will vary in size, depending upon
the size of the item that is being collected. The choice of the packaging will
depend upon the country and/or the laboratory standard method. Integrity
of packaging must be maintained from collection to the laboratory and dur-
ing storage after analysis. Choosing the correct size of packaging and ensur-
ing that the packaging will remain intact for a considerable period of time is
of the utmost importance as this can have serious consequences with regard
to loss of sample, interpretation of results and, ultimately, on the outcome of
a case. Figure 8.29(b) shows an example of fire debris packaged in a nylon
bag, swan-neck sealed.
(a)
(b)
Figure 8.29
(a) Packaging used to sample fire debris at a scene; (b) example of
fire debris sealed in a nylon bag.
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