Measurements of methane leaks may be lower than reality

New York Times : The Environmental Protection Agency requires monitoring of methane levels at natural gas facilities and has approved certain sensors for the purpose. An analysis of one of those devices—the Bacharach Hi Flow Sampler—suggests that unless the device is regularly calibrated it fails to accurately measure levels above a certain point. The device is supposed to switch between two sensors, depending on how high the emissions rate is. Touché Howard, who invented the high-flow-rate sensor in the device, found that when the device is not properly calibrated, it fails to transition from the low-flow sensor to the high-flow one. That means that the reported levels could be tens to hundreds of times lower than the actual levels. Nonetheless, the authors of a recent study that measured methane emissions at US natural gas facilities believe that the levels they measured are accurate because they used multiple systems for collecting their data.