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A vapor calibration system for examining the effects of temperature and humidity on diacetyl measurements.

Jackson-MC; Goldsmith-WT; McKinney-WG; Afshari-A; Frazer-DG
Toxicologist 2010 Mar; 114(1):218
Inhaled diacetyl, a component of butter flavorings, has been shown to be responsible for adverse health effects in microwave popcorn workers and animals. Sampling devices and methodologies to quantitate exposure levels of diacetyl have been shown to be a function of temperature and humidity in the sampling environment. The objective of this investigation was to develop a vapor calibration system (VCS) to calibrate sampling devices under a wide variety of environmental conditions. A custom flow-temperature-humidity controller allowed accurate control of the diluent air input into the VCS. The liquid of interest was injected through a heated port where it was vaporized. The mixed vapor and air were then passed into a Teflon bag. The temperature around the bag was regulated to ensure that the temperature and humidity inside the bag were maintained at user-defined levels and to prevent condensation on the inner walls of the bag. After equilibration, sampling instruments pulled the vapor from the bag for analysis. Computerized valves, heaters, mass flow controllers, temperature sensors, humidity sensors and pressure transducers were utilized to precisely control environmental conditions. Custom data acquisition and control software was developed to automate the calibration process. The real-time response of a set (n=4) of volatile organic meter photo-ionization detectors (MINIRAE 2000) were calibrated for diacetyl with the VCS. Diacetyl concentrations of 5, 75 and 150 PPM were examined at temperatures of 66, 78 and 90F and relative humidities of 5, 30 and 50%. Results indicated a correction factor of 0.73 + 0.12*exp(0.11*AH) needed to be applied to the MINIRAE readings to get the correct diacetyl concentration (AH = absolute humidity mg/L). Future uses for the VCS include calibrating other sensors and sampling methodologies along with different vapors.
Biological-effects; Exposure-assessment; Exposure-levels; Exposure-methods; Inhalation-studies; Microbiology; Microscopic-analysis; Occupational-exposure; Occupational-health; Pulmonary-system; Pulmonary-system-disorders; Quantitative-analysis; Respiratory-hypersensitivity; Respiratory-irritants; Respiratory-system-disorders; Statistical-analysis; Toxic-effects; Vapors; Work-environment; Worker-health; Workplace-studies; Work-practices
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The Toxicologist. Society of Toxicology 49th Annual Meeting and ToxExpo, March 7-11, 2010, Salt Lake City, Utah