Question

Discuss at least 3 different parameters that either were or could be used when comparing your zeolites to charcoal. These do not all have to be chemical properties. You do not have to compare the zeolites to charcoal using all three methods, but at least one of them should have been tested during the project.

Answer 1

OBJECTIVE The objective of this study is to thoroughly explore the properties of two reflecting materials (charcoal and zeolites).

MAIN OUTCOME MEASURES Consumption of volatile anaesthetics using different reflecting materials in filters at different conditions regarding temperature and moisture. CO₂ reflection by the filtering materials: glass spheres, charcoal or zeolite.

RESULTS Isoflurane consumption in an open system was 60.8 g h⁻¹. The isoflurane consumption in dry, warm air was 39.8 g h⁻¹ with glass spheres. Changing to charcoal and zeolite had a profound effect on isoflurane consumption, 11.8 and 10.7 g h⁻¹, respectively. Heating and humidifying the air as well as the addition of N₂O created only minor changes in consumption. The percentage of isoflurane conserved by the charcoal filter was independent of the isoflurane concentration (0.5 to 4.5%). Reflection of sevoflurane, desflurane and halothane by the charcoal filter was similar to reflection of isoflurane. Both charcoal and zeolite filters had CO₂ reflecting properties and end-tidal CO₂ increased by 3 to 3.7% compared with glass spheres. This increase was attenuated to 1 to 1.4% when the air was heated and humidified, and isoflurane was added.

CONCLUSION Charcoal and zeolite possess gas-reflecting properties, which can be used to conserve volatile anaesthetics. They also reflect CO₂. The degree of CO₂ reflection was reduced by heating and humidifying the air.