Field evaluation of a transportable open-path FTIR spectrometer for real-time air monitoring

To effectively and accurately evaluate human exposures to chemicals, it is important to quantify mixtures of chemicals in air, at low levels, and in real time. The purpose of this study was to evaluate, in the field, a prototype of a new transportable instrument that can fill an important gap in methods available to industrial hygienists. This instrument is a cross between extractive and open-path Fourier Transform Infrared spectrometers and measures chemicals passively and in real time in the vicinity of the breathing zone. The spectrometer has a folded optical path that can be enclosed, similar to an extractive system. The enclosure can be removed, enabling the optical path to be open to the atmosphere; thus, the instrument could be operated as an open-path spectrometer. A field study was conducted in three different occupational settings, including a prosthodontics dental laboratory, a surgery recovery area, and a cytology laboratory. Chemicals that were identified and quantified included methyl methacrylate, nitrous oxide, xylene isomers, toluene, and ethanol. Simultaneous side-by-side sampling was conducted with the prototype instrument and recognized National Institute of Occupational Safety and Health (NIOSH) analytical methods. The distinct infrared "fingerprint" of each chemical made identification and quantification of multiple chemicals possible with the prototype instrument. This attribute allowed the industrial hygienist to quantify short-term exposures and ceiling levels, correlate work practices with concentration levels, evaluate the effectiveness of engineering controls, and identify the presence of unexpected compounds. There was no significant difference between the mean time-weighted averages (TWAs) of the prototype instrument and traditional methods (p > 0.03). Regression analysis found good correlation between the two methods with no significant differences between the slope and unity and between the y-intercept and zero (p > 0.03). The technology and design of the prototype instrument incorporated a unique combination of features and advantages not found in other methods or instruments. The instrument produced results comparable to recognized analytical methods under field conditions and shows promise as a powerful tool in industrial hygiene air monitoring applications.