Hydrocarbon Vapor Standards for Performance Evaluation of Combustible Gas Detectors

• NCJ Number: 79907
• Author(s): J E Brown
• Date Published: 1981
• Length: 16 pages
• Sponsoring Agency: National Institute of Justice (NIJ); US Dept of Justice NIJ Pub
• Corporate Author: US Dept of Commerce
• Sale Source: Superintendent of Documents, GPO; National Institute of Standards and Technology (NIST); National Institute of Justice/
• Language: English
• Country: United States of America
• Note: Limited number of copies available free from NBS - Law Enforcement Technology Special Publication.

Annotation

This research was undertaken to develop standards of low concentrations of organic vapors that could be used by fire investigators to calibrate and evaluate the performance of hydrocarbon vapor detectors, also known as combustible gas detectors or 'sniffers.' These detectors are used to ascertain the presence of accelerant vapors in cases of suspected arson.

Abstract

Calibration mixtures of hydrocarbon vapor were prepared for the study. The standards contained vapors of aliphatic and aromatic compounds common to petroleum distillates, such as gasolines, which are frequently employed as accelerants in arson fires. These standards were prepared by a dynamic dilution technique in which the vapor evolving from diffusion tubes containing liquid hydrocarbons was diluted with air. The concentrations of the vapors were calculated from gravimetrically determined diffusion rates of the hydrocarbons and from measured flow of air at three temperatures: 30, 50, and 70 degrees centigrade. Gas chromatographic analyses of the vapor-air mixtures generated at 30 and 50 degrees centigrade showed that the vapor concentrations are essentially constant within 10 percent and from one period to another and that they agreed with calculated concentrations. Graphs, diagrams, data tables, and eight references are supplied. (Author abstract modified)