Government of Ontario

CFS - Technical Information Sheets - Chemistry - Fire

Centre of Forensic Sciences

Technical Information Sheets

Chemistry


Fire Debris Analysis Information – PDF, 30 kb


Introduction

Items collected in the investigation of a fire may be examined at the laboratory for the presence of volatile ignitable liquids and/or hydrocarbon gases. When these liquids or gases are used to set, spread or increase the intensity of a fire, they are referred to as “accelerants.” Items related to the fire may include burnt debris, clothing, or samples of liquid. The identification of volatile ignitable liquids and/or hydrocarbon gases in submitted items does not necessarily indicate that the crime of arson has been committed. All laboratory results must be evaluated in the context of the fire investigation.

Packaging

When packaging items suspected of containing volatile ignitable liquids and/or hydrocarbon gases, it is vital that a protective seal is provided against evaporation from the container and from external contamination. Recommended packaging includes sealed glass Mason jars and specialty nylon bags. Common plastic bags are not acceptable. Samples of liquid should be submitted in glass vials with foil-lined lids.

An unused jar should also be submitted for comparison purposes. The comparison jar is used to reflect the storage and handling history of the jars used to package the submitted items. The comparison jar and the associated jars should have an identical cleaning, storage, and handling history.

Examination

Visual Examination

All items are visually examined to check the seal numbers (if present), the contents and the integrity of the packaging.

Instrumental Analysis

Samples of vapour or liquid are removed from the items, using a syringe, for analysis by Gas Chromatography-Mass Spectrometry (GC-MS). Gas chromatography is a standard analytical technique that separates the components of a sample and generates a chart known as a chromatogram. Ignitable liquids are identified by their distinctive patterns in these chromatograms. Mass spectrometry assists in classifying and identifying the components of the sample. This laboratory does not determine the quantity of any volatile ignitable liquid identified in an item as it cannot be related to the quantity of liquid originally present at the scene.

Liquid Recovery

Liquid recovery by steam distillation may be undertaken when the results of instrumental analysis indicate that liquid recovery may be possible. Distillations are done when required for identification or when otherwise determined by the scientist to be of value in interpretation. The submitter may consult with the scientist to determine whether there are circumstances that make distillation appropriate in their case.

Quantities of liquid recovered by distillation cannot be correlated to the total volume of liquid originally present at a scene.

Interpretation

Volatile ignitable liquids identified at a level significantly above the detection limit of our instruments are reported as “[Volatile ignitable liquid] was identified in item X”. Volatile ignitable liquids identified near but above the detection limit are reported as “A trace amount of [volatile ignitable liquid] was identified in item X”. Determination of what constitutes a trace amount is made on a case-by-case basis by the reporting scientist and is based on consideration of several variables, including instrument response, amount of debris, condition and type of debris, and analysis conditions.

Comparison jars are analyzed to address the possibility that any trace level findings of volatile ignitable liquids identified in the submitted items could have been contributed by contamination of the jar prior to use or cross-transfer from other items during storage and handling.

Certain types of debris may contain background materials that can affect volatile ignitable liquids analysis. The investigator may submit comparison samples to assist with identification and/or interpretation of any volatile ignitable liquids identified in such types of debris.

Some volatile ignitable liquids, such as turpentine and styrene, may naturally originate from materials present in the debris, and will therefore not routinely be reported.

Identification of non-volatile ignitable liquids, such as motor oil and cooking oil, requires a separate analysis and is not routinely performed. A specific request for non-volatile ignitable liquids must be made on the submission form if this examination is desired.

Unless requested by the investigator or otherwise stated in the report, no attempt is made to specifically identify the debris in submitted items.


Glossary

Comparison Jar
An unused glass Mason jar with the same storage and handling history as the jars used to package the submitted items.

Comparison Sample
A sample of the same material/debris selected for volatile ignitable liquid analysis that is not suspected to contain any volatile ignitable liquid.

Control Sample
Material obtained directly from an uncontaminated source, such as a manufacturer or retail store.

Debris
Materials collected at a fire scene. These materials may include carpet, underlay, concrete, wood, fabric, newspaper, cardboard, plastics, tile, plaster and liquids.

Detection limit
The lowest concentration of a material that can be identified using a given instrument and method of analysis.

Flash point
The lowest temperature at which an ignitable liquid produces sufficient vapours to support a momentary flame.

Hydrocarbon gases
Petroleum products that are ignitable gases at normal temperatures and pressures. This includes natural gas, propane and butane. Propane and butane can be stored and shipped under pressure as liquid petroleum gases.

Ignitable liquid
Any liquid that is capable of fueling a fire.

Volatile ignitable liquid
An ignitable liquid that readily generates vapours. Examples of such liquids include some petroleum products, alcohols and some solvents.

Non-volatile ignitable liquid
An ignitable liquid that does not readily generate vapours. Examples include ignitable oils such as cooking and motor oils.

Petroleum products
A wide range of products derived from the processing of crude petroleum oil. The most commonly encountered petroleum products can be classified as one of the following:

Gasoline
Includes all brands and grades of gasoline

Light petroleum distillates
Includes camping fuel and pocket lighter fuel

Medium petroleum distillates
Includes mineral spirits, some paint thinners, some charcoal starter fluids and some products marketed as kerosene

Heavy petroleum distillates
Includes fuel oil, diesel fuel and some products marketed as kerosene

(Specialty solvents may also be encountered – isoparaffinic, aromatic, napththenic-paraffinic, and normal alkane products– in commercial products such as lamp oils, fuel additives, adhesives, cleaning products, paint thinners, and charcoal starter fluids.)

Vapour
A gas produced by the evaporation of a liquid that may mix with air or other gases.

Volatile
Readily evaporates at normal temperatures and pressures.