Using a portable heat sealer for sealing Nylon 11 (polyamide 11) arson evidence bags

The containers used in the collection of suspected arson evidence are expected to contain an array of chemicals potentially utilised to accelerate fires, their residues and the products generated during combustion. The permeability of the materials used in these containers and the ability to seal these containers are essential to the preservation of this evidence. As such, Nylon 11 (polyamide 11) is typically used for this purpose in the UK. The aim of this research was to evaluate the process of heat sealing, and the potential use of a portable heat sealing device, for sealing Nylon 11 arson evidence bags at the crime scene.
During this study it was found that manual heat sealing of Nylon 11 bags provided consistent seals, that would retain volatile organic compounds, and that these could be easily assessed for their integrity. It was also found that impulse heat sealers could be made portable by the use of a power inverter, meaning that this method of sealing could be performed using the 12 v DC supply of domestic vehicles without the need for an additional power supply at the scene.
The study found that some commercially available arson evidence bags were supplied improperly sealed and therefore posed a potential risk by providing the opportunity for the loss of or the contamination of Volatile Organic Compounds within the bags. The heat seals in the bags obtained were with the exception of one supplier found to be less consistent with regards to the tensile strength than those manually produced.
The ability to produce heat seals in the scene therefore provides great potential.