ARTICLES

Research & Protocol

Absorbent collection of ignitable liquid residue from concrete
Prepared by Noel Putaansuu and
Dale Mann of MDE

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RCW Immunity Letter

for public investigators to get a copy of the private (insurance) investigation

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RESEARCH & PROTOCOL

Absorbent collection of ignitable liquid residue from concrete
Prepared by Noel Putaansuu and Dale Mann of MDE

Keep in mind that the surfaces to be sampled can not have any standing water on them (wet surfaces are problematic to powder saturation). Allow any standing water to dissipate/evaporate naturally to dryness prior to applying the absorbent. Do not heat the concrete to dry it. 60 minutes is sufficient time to allow the absorption to take place. Sweep the powder up with a new disposable brush and place in an appropriately sized can for laboratory analysis. Take the time to vigorously sweep up the fines as they have had the most intimate contact with the surface of interest.

A comparison sample should be prepared as well. Select an area well separated from the area of interest and repeat the sampling process. Remember it is imperative to also send a control sample of the absorbent to the laboratory for comparison purposes.Unscented clay cat litter was found to be a readily available, inexpensive and an effective absorptive media. The cat litter can be lightly ground to reduce the particle size. (Finer particles increase the exposed surface and are more effective in the absorption process on concrete.) Prepare the cat litter by heating several pounds at 121°C (250°F) overnight in a shallow dish. After cooling, package quantities in one-quart cans (or other vapor-tight container) for future use. This is a convenient quantity and generally will provide sufficient material for a single fire scene.

Sampling Supplies:
• Pre-conditioned cat litter (unscented)
• Clean cans to contain samples
• New paint brushes (one for each sample)
• Disposable scoops (stiff paper is adequate)
• Clean plastic tenting material to protect the site during the waiting period (optional)

Procedure:
• Clean and dry the area to be sampled
• Photograph/document the sample area
• Spread the absorbent powder over the area to be sampled
• Record the time that the absorbent is applied
• Photograph/document the sample area and absorbent
• Wait a minimum of 60 minutes
• Sweep up the sample on to the collection tray (clean brush and tray)
• Record the time
• Deposit into the can, seal and label.
• Dispose of the brush and tray

Samples going to the lab
• Subject area (area of origin)
• Comparison area (representative of site but outside the area of origin)
Control sample of absorbent powder (clean/unused)

IAAI of Washington
Arson Investigators
IAAI of Washington
IAAI of Washington