# Calibration-free benzene sensor for fire environments based on interband cascade laser absorption spectroscopy near 5 μm

## TL;DR

This paper introduces a portable, calibration-free benzene sensor using laser absorption spectroscopy for measuring toxic emissions in fire environments.

## Contribution

A novel, robust, and portable benzene sensor based on interband cascade laser absorption spectroscopy near 5 μm is developed for fire environments.

## Key findings

- The sensor can measure benzene over a wide dynamic range from sub-ppm to thousands of ppm.
- The sensor remains stable during long-term continuous logging and effectively accounts for interferers in fire effluents.
- The sensor uses a multi-pass Herriott cell to achieve portability with sufficient optical pathlength.

## Abstract

The toxicity of effluents from fires that occur at the wildland-urban interface is a growing concern among first responders, health professionals, and local populations. Benzene (\documentclass[12pt]{minimal}
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\begin{document}$$\hbox {C}_{6}\hbox {H}_{6}$$\end{document}) is a key fire emission of particular concern because of its high carcinogenicity. To better understand \documentclass[12pt]{minimal}
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\begin{document}$$\hbox {C}_{6}\hbox {H}_{6}$$\end{document} production in harsh fire environments, this paper presents a calibration-free scanned-wavelength interband cascade laser absorption spectrometer for \documentclass[12pt]{minimal}
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\begin{document}$$\hbox {C}_{6}\hbox {H}_{6}$$\end{document} that is demonstrated to be robust, portable, and accurate. The spectrometer targets a narrow-band absorption feature located near 2006 cm−1 (\documentclass[12pt]{minimal}
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\begin{document}$$\lambda _0 = 5~\mu $$\end{document}m). This wavelength selection is shown to be advantageous for measurements at near-ambient pressure conditions and to be well-suited for robust spectrally-resolved measurements with the limited scanning range of modern interband cascade lasers. The sensor employs a multi-pass Herriott cell to achieve an increased optical pathlength in a volume small enough to make the sensor portable for field measurements. The sensor is demonstrated to measure \documentclass[12pt]{minimal}
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\begin{document}$$\hbox {C}_{6}\hbox {H}_{6}$$\end{document} over a wide dynamic range (sub-ppm to thousands of ppm) relevant to first-responder exposures. The method is also shown to remain stable over long durations of continuous logging and to effectively measure \documentclass[12pt]{minimal}
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\begin{document}$$\hbox {C}_{6}\hbox {H}_{6}$$\end{document} content in structural fire effluents with varying ventilation conditions, accounting for potential interferers.