Pyrolysis
Definition
The thermal decomposition of cellulose in paper at approximately 150 to 300 degrees Celsius, disrupting glycosidic bonds and releasing water and carbon dioxide, converting the paper matrix progressively from intact fibres through brownish degradation products to amorphous carbon char.
- Temperature range
- 150-300°C for paper cellulose decomposition
- Oxygen requirement
- Limited or absent (distinguishes pyrolysis from combustion)
- Key products
- Volatile fuel vapours, char, water, and carbon dioxide
Common questions
What happens to paper during pyrolysis?+
Pyrolysis heats paper to 150-300°C without sufficient oxygen, breaking the glycosidic bonds in cellulose. The paper progressively darkens through brownish degradation before converting to amorphous carbon char. Water and carbon dioxide are released during this process.
Why is pyrolysis important in arson investigation?+
Pyrolysis precedes actual combustion. It thermally decomposes organic material and produces volatile fuel vapours that mix with air and ignite, making it the critical first step in fire development. Understanding pyrolysis helps investigators reconstruct how a fire started and spread.
How does pyrolysis complicate fire evidence analysis?+
Pyrolysis generates complex mixtures of smaller organic molecules, including hydrocarbons that mimic ignitable liquid patterns in GC-MS testing. This creates background interference that must be subtracted to avoid misidentifying pyrolysis products as accelerants.
Related terms
- 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...
- 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...
- Ashing
- The terminal stage of heat damage, above approximately 400 degrees Celsius, in which carbon oxidises to carbon dioxide and only inorganic mineral...
- ASTM E1188
- Standard Practice for Collection and Preservation of Information and Physical Items by a Technical Investigator, the companion evidence-preservation standard to NFPA 921...
- Backdraft
- A deflagration event triggered when air is suddenly admitted to a compartment where a fire has been oxygen-depleted but has continued to...
- Background Subtraction
- The analytical practice of comparing fire debris EIPs against comparison sample EIPs from unburned substrate of the same type. Features present in...
- Charring
- The stage of heat damage at approximately 200 to 400 degrees Celsius at which paper cellulose converts to amorphous carbon; the sheet...
- 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...
- Consolidant
- A dilute polymer solution (Paraloid B-72, Klucel G, Cellugel) misted over a fragile char surface to stabilise the carbon matrix before handling...
- Controlled Humidification
- Exposure of a charred document to 85 to 90 per cent relative humidity inside a sealed chamber, temporarily restoring pliability to the...
- Equivalence Ratio
- The ratio of actual fuel-to-air ratio to the stoichiometric fuel-to-air ratio. An equivalence ratio above 1 (fuel-rich) produces CO, soot, and unburned...
Explained in these topics
- Charred and Burnt Document Recovery and DeciphermentThe thermal decomposition of cellulose in paper at approximately 150 to 300 degrees Celsius, disrupting glycosidic bonds and releasing water and carbon dioxide...
- Fire Chemistry, Pyrolysis and the Arson Investigation FrameworkThermal decomposition of organic material under heat, with limited or no oxygen, producing volatile fuel vapours and char. Pyrolysis precedes combustion and ge...
- Pyrolysis Products, Substrate Interferents and Background SubtractionThermal decomposition of organic material at elevated temperature in the absence of sufficient oxygen for complete combustion. Produces a complex mixture of sm...