A gas and vapor generation system with programmed automatic cyclic output.
Am Ind Hyg Assoc J 1984 Feb; 45(2):138-142
A gas and vapor generation system with programmed automatic cyclic output was described. The system consisted of a constant concentration gas or vapor generation subsystem and a modified mass flow controller interfaced with a time based programmable signal generator. The signal generator was fitted with a match/pac signal conditioner to provide an output signal compatible with the full scale input of the mass flow controller. The final output of the generating system could be controlled over a specified range of concentrations, and the concentration versus time profile could be reproduced at preset intervals ranging from a few minutes to several hours. The system contained two linear mass flow meters and associated controllers, one for the contaminant stream flow and one for the dilution flow. The program used in the signal generator was produced by manual etching onto a program card, with the abscissa representing time and the ordinate percent full scale output to the flow controller valve. Output from the generator was monitored continuously by a flame ionization detector and gas chromatograph. The system was tested with toluene (108883) and carbon-monoxide (630080). The data showed good reproducibility between cycles within a run and between runs on separate days. For example, with toluene the mean peak height from the gas chromatograph had a standard deviation of less than 1 percent from cycle to cycle within a run and less than 3 percent from day to day. The author concludes that the system is capable of producing reproducible cycles of varying contaminant concentrations with good precision.
NIOSH-Author; Laboratory-equipment; Controlled-atmospheres; Gases; Organic-vapors; Analytical-instruments; Data-processing; Laboratory-testing; Gas-meters; Air-sampling
American Industrial Hygiene Association Journal