CAFS And Its Impact In Fire Scene Investigations

Investigators were concerned about how the use of the foam would impact the use of accelerant detection canines, conceal scene hazards or create slippery conditions and how much time was required for the foam to dissipate in order to conduct an origin and...


  • Both rooms had gone to flashover and produced considerable damage
  • There was considerable charring to all furnishings
  • The flooring was charred
  • The fire was extinguished with a controlled application of Compressed Air Foam
  • The Compressed Air Foam seemed to dissipate fairly quickly
  • There was not a large amount of foam, but pockets remained for over one hour in Test # 2
  • Do to the minimal amount of foam - no slip hazard was detected

Fire Investigator Wilson and his partner Iris were closely monitored throughout the entire process and the following observations were made:

  • There was no apparent difficulty in conducting a K-9 scene safety check
  • The Compressed Air Foam used for extinguishment did not give K-9 Iris any problems conducting her search for the ignitable liquids
  • The Compressed Air Foam had dissipated sufficiently for canine Iris and Investigator Wilson to conduct their search of the entire scene and mark Iris' primary alerts
  • Investigator Wilson was able to accurately mark K-9 Iris' alerts and collection of these alerts was done without problem.

Laboratory Analysis

The samples collected from both of the test burns and a sample of the foam was submitted to the ATFE National Lab for analysis. The chemical make-up of the foam was consistent with what would be expected for such a product. However, there were some components in the foam that may interfere with ignitable liquid analysis. These components could be classified as a heavy normal-alkane product by ASTM E 1618. These components, if observed in debris or in combination with a heavy petroleum distillate such as kerosene or diesel, may pose some problems with chromatographic analysis.

Three of the four samples collected from Test 1 were positive for the presence of a medium petroleum distillate (MPD), which is consistent with the use of the Kingsford brand charcoal lighter fluid. Only one of the four samples collected from Test 2 was positive for the presence of gasoline. For these positive samples, the chemical components of the foam did not interfere with the analysis of the data.

One of the three negative samples from Test 2 had indications of gasoline, but the level was too low to make a positive identification. The remaining two negative samples from Test 2 and the negative sample from Test 1 showed no indications of their respective ignitable liquids (gasoline and MPD). In fact, the chemical components from the foam predominated the observed chromatographic data for all of the negative samples. The reasons for the negative laboratory results for some of the samples may be due to various reasons. One possibility may be the amount of time from when the samples were collected to when they were analyzed. The collected samples were analyzed approximately 30 days after the tests. This possible effect of the foam on the collected samples needs to be examined further under controlled conditions.

Conclusions

Based upon the review of existing research and the fire tests conducted, it is believed that the Compressed Air Foam did not interfere with the ability of the ATF-certified accelerant detection canine's or the handler's ability to conduct an effective scene search, marking or collection of potential evidence. In addition, no significant impact was noted to the fire scene investigation in the tests. However in Test #2, the foam did remain in pockets on the floor for over one hour after application. The foam was minimal and it is not believed that this would have created a significant problem for fire investigators. Should more foam have been used, it may have caused a delay in the scene investigation, obscured hazards or presented a slip hazard. Even though some of the samples tested positive for the presence of the respective ignitable liquids, the overall effect of the foam on laboratory analysis needs to be evaluated further.

Recommendations

  • Firefighters receive adequate training in the proper application of Compressed Air Foam to avoid excessive amount of foam build-up
  • Fire investigators take a proactive approach to familiarize themselves with the product and the foam application procedures if their department is using or is planning to utilize Compressed Air Foam
  • Fire investigators and canine handlers conduct a more comprehensive scene safety search when Compressed Air Form has been applied to ensure that no hazards could be obscured by the foam
  • Fire investigators must ensure that a control sample of the Compressed Air Foam that was used to suppress the fire is submitted to the lab with other evidence that has been collected
  • Additional laboratory testing and evaluation is still needed to determine the effects of Compressed Air Foam on ignitable liquids
  • Canine handlers and fire investigators should obtain a Material Safety Data Sheet on the foam that is being used within their departments prior to any exposures