SWGFEX Type C Interferent List
Definition
A documented list maintained by the Scientific Working Group for Fire and Explosion Investigation (and continued by OSAC) of substrates known to produce GC-MS patterns that can meet E1618 classification criteria. Includes polypropylene, polyurethane foam, SBR rubber, asphalt, and PVC plasticisers.
- Maintained by
- SWGFEX, continued by OSAC
- Field
- Fire debris analysis
- Example substrates
- Polypropylene, polyurethane foam, SBR rubber, asphalt
- Relevance
- Can mimic ASTM E1618 ignitable-liquid classification patterns
Common questions
Why does a substrate needing this list matter if it never contained an accelerant?+
Certain plastics and materials produce pyrolysis products during burning that closely resemble the GC-MS chromatogram of an ignitable liquid class under E1618 criteria, so an examiner unaware of the interferent list could misclassify pyrolysed substrate as evidence of an accelerant that was never present.
How does an examiner use the interferent list in practice during fire debris analysis?+
Before concluding that an ignitable liquid is present, the examiner checks whether known substrate materials from the fire scene, matched against the interferent list, could explain the observed pattern, and factors that possibility into the interpretation rather than reporting a false positive.
Related terms
- 4-Vinylcyclohexene (4-VCH)
- A pyrolysis product of styrene-butadiene rubber (SBR) carpet backing, appearing at m/z 108 in the GC-MS. Elevated m/z 108 in a fire...
- Alkene Triplet Pattern
- The GC-MS signature of polypropylene pyrolysis: a repeating triplet of n-alkane, 1-alkene (terminal double bond), and diene peaks at each carbon number...
- Background Subtraction
- The analytical practice of comparing fire debris EIPs against comparison sample EIPs from unburned substrate of the same type. Features present in...
- Comparison (Control) Sample
- A sample of unburned substrate collected from the same room or proximate unburned area as the fire debris sample, of the same...
- Principal Component Analysis (PCA)
- A multivariate statistical method used in fire debris research to reduce chromatographic data matrices to principal components that capture major variance. Used...
- Pyrolysis
- The thermal decomposition of cellulose in paper at approximately 150 to 300 degrees Celsius, disrupting glycosidic bonds and releasing water and carbon...
- Substrate Interferent
- A pyrolysis product from building or furnishing material that produces a GC-MS chromatographic pattern overlapping with or resembling an ignitable liquid category...
- Type C Interferent (E1618)
- ASTM E1618 designation for a substrate whose pyrolysis products can produce a chromatographic pattern meeting the criteria for an ignitable liquid category....
- Unresolved Complex Mixture (UCM)
- The broad hump of hundreds of co-eluting cycloalkane and isoalkane compounds in the TIC of heavy petroleum products (diesel, heavy fuel oil,...