Quantification of hydrogen cyanide in fire effluent

Hydrogen cyanide is often the most toxicologically significant component in fire effluents from nitrogen-containing materials. Unlike the other major asphyxiant, carbon monoxide, sensors for continuous hydrogen cyanide quantification, at and above dangerous concentrations, are not commercially available. This article investigates the analysis of fire effluent captured in bubbler solutions, by colorimetric quantification of hydrogen cyanide using chloramine-T/isonicotinic acid. The bubbler samples were mixed with colorimetric reagents to give a blue dye in response to cyanide ions. A novel reaction scheme accounting for the formation of the blue dye from cyanide ions is presented. Dilute, standard cyanide solutions were found to be stable after storage for up to 1 year. Alkaline bubbler solutions, through which the fire effluent has passed, showed consistent cyanide concentrations, for samples stored between 5°C and 21°C, for up to 31 days after sampling. The effect of other common ions likely to be present in fire effluent solution samples (CO32−, SO32−, SO42−, NO2− and NO3−) was investigated for their potential interference. The most significant interference was sulphite which reduced the apparent cyanide concentration by 13% at 10 mg L−1SO32− concentration.