New Method of Destroying Waste Anesthetic Gases Using Gas-Phase Photochemistry.

BACKGROUND: The inhalation anesthetics are potent greenhouse gases. To reduce the global environmental impact of the health care sector, technologies are sought to limit the release of waste anesthetic gas into the atmosphere. METHODS: Using a photochemical exhaust gas destruction system, removal efficiencies for nitrous oxide, desflurane, and sevoflurane were measured at various inlet concentrations (25% and 50%; 1.5%, 3.0%, and 6.0%; and 0.5%, 1.0%, and 2.0%, respectively) with flow rates ranging from 0.25 to 2.0 L/min. To evaluate the economic competitiveness of the anesthetic waste gas destruction system, its price per ton of carbon dioxide equivalent was calculated and compared to other greenhouse gas abatement technologies and current market prices. RESULTS: All inhaled anesthetics evaluated demonstrate enhanced removal efficiencies with decreasing flow rates (P < .0001). Depending on the anesthetic and its concentration, the photochemical exhaust gas destruction system exhibits a constant first-order removal rate, k. However, there was not a simple relation between the removal rate k and the species concentration. The costs for removing a ton of carbon dioxide equivalents are <$0.005 for desflurane, <$0.114 for sevoflurane, and <$49 for nitrous oxide. CONCLUSIONS: Based on this prototype study, destroying sevoflurane and desflurane with this photochemical anesthetic waste gas destruction system design is efficient and cost-effective. This is likely also true for other halogenated inhalational anesthetics such as isoflurane. Due to differing chemistry of nitrous oxide, modifications of this prototype photochemical reactor system are necessary to improve its removal efficiency for this gas.

Total Absorption Cross Section for UV Excitation of Sulfur Monoxide.

In a new study on sulfur monoxide, new ab initio potential energy curves are developed for excited states A3Π, B3Σ-, C3Π, and C'3Π and for three states that are unassigned in the literature, which we numerically name 33Σ-, 43Π, and 53Π. All these excited states have allowed transitions from ground state, X3Σ-. The ab initio calculations were performed using the MRCI-F12+Q/aug-cc-pV(5+d)Z level of theory implemented in MOLPRO2015. On the basis of close-coupling R-matrix theory, fine structure absorption cross sections of isotopically substituted sulfur monoxide are calculated for wavelengths of 190-300 nm. The spectra are shown at the highest possible resolution (FWHH ≈ 0.15-0.18 cm-1) for reference and future studies. The effects of self-shielding and possible mutual shielding are discussed.