Detection of SOF Using a Photoacoustic Two-Chamber Approach.

The wide use of sulfuryl difluoride (SOF) for termite control in buildings, warehouses and shipping containers requires the implementation of suitable sensors for reliable detection. SOF is highly toxic to humans and the environment, and moreover, it is a potent greenhouse gas. We developed two photoacoustic two-chamber sensors with the aim to detect two different concentration ranges, 0-1 vol.-% SOF and 0-100 ppm SOF, so that different applications can be targeted: the sensor for high concentrations for the effective treatment of buildings, containers, etc., and the sensor for low concentrations as personal safety device. Photoacoustic detectors were designed, fabricated, and then filled with either pure SOF or pure substituent gas, the refrigerant R227ea, to detect SOF. Absorption cells with optical path lengths of 50 mm and 1.6 m were built for both concentration ranges. The sensitivity to SOF as well as cross-sensitivities to CO and HO were measured. The results show that concentrations below 1 ppm SOF can be reliably detected, and possible cross-sensitivities can be effectively compensated.