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...

An ATF-certified accelerant detection canine, Iris, and handler Doug Wilson from the Anne Arundel County, MD, Fire Investigators' Office, were utilized to examine the fire scene. The following issues were of specific concern to the fire investigators and the accelerant detection canine team:

  • Would the use of foam prevent the handler from performing a scene safety check to protect the canine?
  • Would foam hinder the search capabilities of the canine?
  • Would the foam prevent the accurate marking of the canine alert site?
  • Would foam contaminate the accelerant sample or be washed away or diluted to the point that it would not show up during a canine search or lab analysis?

Test #1

Test # 1 was a room and contents fire with approximately three to four cups of commercially available Kingsford brand charcoal lighter fluid poured across the floor covering and over to a double bed. The liquid was spread in a standard "trailer" fashion recognized by fire investigators. The liquid was ignited and allowed to burn to post flashover.

In Test # 1, the limited amount of charcoal lighter fluid utilized resulted in a slow growing fire. As a result, there was not rapid fire growth and it took nearly 15 minutes for the contents to become involved and reach flashover conditions. Fire suppression was conducted approximately one minute later with the application of Compressed Air Foam from a single handline at a setting of five-percent (0.5%). The nozzle man was an experienced CAFS user and applied the foam judiciously. Little or no visible foam was observed within the compartment after fire suppression.

Ofter approximately 30 minutes, ATF personnel monitored the atmosphere until it was safe to enter. Once it was safe to enter, Investigator Wilson calibrated his canine partner Iris on a drop of 50-percent evaporated gasoline placed on a piece of carpet outside of the scene. This calibration is per ATF canine training and serves several purposes. First it lets the handler know that his canine partner's nose is working and second it lets the canine know they are going to work. Fire Investigator Wilson conducted a search of the fire scene with Iris, who gave numerous primary alerts. Four samples were collected and placed in clean metal evidence cans. The collected samples were placed in a discrimination line for the canine. This discrimination line examination provided confirmation of the canine alerts made in the scene.

Test #2

The second room and contents fire was set by using approximately one to one-and-one-half quarts of gasoline, which was poured across the floor covering, over chairs and up onto a table and chairs. This fire grew extremely rapidly and progressed to flashover in approximately two minutes. After an additional minute, fire suppression was initiated using CAFS from a single handline at a setting of three-percent. However in this test, the experienced nozzle man was instructed to apply additional amounts of foam to replicate an inexperienced or novice user. It was believed that this may more accurately represent a real fire scene where more foam is utilized.

After fire suppression, foam was visible in pools on the floors and other horizontal surfaces. It appeared that the foam pooled in lower areas, much as water would pool. The remaining foam, however, was not excessive enough to cause a delay in the fire scene investigation. Some of the remaining foam could obscure small items at floor level. Yet, it was not perceived that the lingering foam created a safety hazard by obscuring openings or large objects. After approximately 20 minutes, pockets of foam were still visible on the floor and under a desk. This slowly dissipated over the next hour until it was nearly invisible.

As in the first test burn, the atmosphere was monitored and once it was safe to enter, the accelerant detection canine team conducted a search using the same protocol as for the first room. The canine gave numerous primary alerts, and four samples were again collected and placed in clean metal evidence cans. The collected samples were placed in a straight line and a discrimination line examination was again conducted by canine Iris.


At the conclusion of both tests at the ATF Fire Research Laboratory, the following observations were made by the members of the project team.