Drilling and fracking activities are relatively short-term operations, but compressor stations are semi-permanent facilities that pollute the air 24 hours a day as long as gas is flowing through pipelines. Day-to-day emissions from compressor stations are subject to highly episodic variations due to pressure changes and maintenance-related deliberate releases and can create periods of potentially extreme exposures. Pipelines themselves can freeze, corrode, break, and leak. Between January 2010 and November 2017, according to data from the federal Pipeline and Hazardous Materials Safety Administration, pipeline incidents killed 100 people, injured 500, prompted the evacuation of thousands, and leaked more than 17 billion cubic feet of methane. Low-pressure flow lines alone are responsible for more than 7,000 spills and leaks since 2009.