Workplace and environmental air contaminant concentrations measured by open path fourier transform infrared spectroscopy: a statistical process control technique to detect changes from normal operating conditions.
Malachowski-MS; Levine-SP; Herrin-G; Spear-RC; Yost-M; Yi-Z
Air Waste 1994 May; 44(5):673-682
The ability of a statistical processing control technique designed to be used with open path/Fourier Transform infrared (OP/FTIR) spectroscopy to detect deviations from normal operating conditions during industrial processes was evaluated. A Nicolet OP/FTIR spectrometer interfaced to a personal computer was tested under laboratory conditions by placing it in an experimental chamber where it was exposed to fluctuating concentrations of acetone (67641) vapor for 15 minutes (min). High or low flow rates with or without fans were used to simulate various industrial ventilation systems. A second source of acetone was then used to simulate a leak for another 15min, representing a deviation from normal operating conditions. Acetone concentrations were measured in real time by the OP/FTIR spectrometer. Consecutive measurements of acetone concentration were plotted against time to create sets of time series data. The data were fitted to appropriate dynamic models to remove any effects of sequential measurements. The corrected time series data were analyzed by Shewhart and exponentially weighted moving area (EWMA) control charts to identify any deviations from normal operating conditions. A similar field experiment was performed in which acrylonitrile (107131), 1,3-butadiene (106990), and styrene (100425) emissions from the production area of a polymerization facility were monitored. The Shewhart control chart was able to detect the simulated acetone leak in the laboratory simulation under a high flow/no fan condition. The EWMA control chart detected the simulated leak under a low flow/with fan condition. Field monitoring and analysis with both the Shewhart and EWMA control charts showed that at times the concentrations of styrene and 1,3-butadiene were higher than normal. The acrylonitrile concentrations remained within the normal range. The authors conclude that OP/FTIR spectrometry when combined with statistical process control techniques can be used for applications such as signaling of an alarm or warning, increasing levels of worker respiratory protection, or evacuation of a community when toxic gas or vapor concentrations are determined to be out of control.
NIOSH-Publication; NIOSH-Grant; Grants-other; Analytical-methods; Infrared-spectroscopy; Spectrographic-analysis; Statistical-analysis; Industrial-hygiene; Analytical-instruments; Organic-vapors; Laboratory-testing; Simulation-methods; Industrial-processes; Safety-research; Workplace-monitoring; Mathematical-models
Environmental & Indust Health University of Michigan 1420 Washington Heights Ann Arbor, MI 48109-2029
67-64-1; 107-13-1; 106-99-0; 100-42-5
University of Michigan at Ann Arbor, Ann Arbor, Michigan