After the heat of the fire, the dilution by extinguishing practices, and further weathering by environmental and sometimes microbial factors, the samples are often both very weak and very weathered. Actlabs has continually advanced the science to improve both the sensitivity and focus of the method for the detection of flammable liquids in order to provide the best analysis for these weak samples.
At these low concentrations, the background of hydrocarbons from newly purchased mason jars can complicate the analysis. These hydrocarbons are in the medium to low parts-per-billion range which can be detected by our method. The hydrocarbons are on the glass surface and surfaces of the tin lid. Through our testing, we believe that the source of these compounds is from the manufacturing process, the cardboard shipping material and from contamination of the cardboard during shipping from the manufacturer. We do not believe this contamination to be from the red sealing ring although this may have been a problem with older jars having separate seals. To improve the analysis of weak samples, we have devised a simple method of cleaning the mason jar and lid that the Fire Investigator can do prior to going out to the field site.
We recommend using nylon evidence bags or a pre-cleaned mason jar. The mason jar allows for longer sample storage, easier analysis and better sample integrity than a nylon bag or tin container.