DO IT YOURSELF: EVALUATING COMMERCIAL CO2 REGULATORS FOR SURVEILLANCE NETWORKS USING PRESSURIZED CYLINDERS.

Abstract

Carbon dioxide (CO2) is a universal attractant for monitoring blood-feeding insects, such as mosquitoes. Although dry ice has been the historical benchmark, compressed gas cylinders can be used in tandem with a gas regulator to control CO2 flow rate more precisely. The literature is sparse on best practices regarding how to choose or test regulators. We evaluated four commercially available regulator types from beverage and welding suppliers and compared them to a previously tested regulator used at the Salt Lake City Mosquito Abatement District (SLCMAD). Using environmental chambers, we simulated both the temperature drop of spring/fall or summer nights down to 9°C, as well as daytime highs within the seasonal expectations of the central ranges of Utah, up to 42°C. Two regulators failed to maintain calibrations in these screenings. The remainder were vetted by acquiring duplicates and rerunning the simulations with inverted temperature exposures, starting low and heating up, instead of starting warm and cooling down in the first tests. The remaining regulators were tested in the field for validation. After 56 trap cycles with 15 duplicates of three regulator models, general failure rates in real applications all decreased below 5% of total uses. The preexisting regulator used by SLCMAD performed well in simulations, but had double the failure rate of the other screened models. We use this study to highlight the scarcity and importance of conducting evaluations on the existing protocols or equipment for public health vector control programs and provide recommendations for addressing operational usage.