Fugitive emissions are leaks and other irregular releases of gases or vapors from a pressurized containment – such as appliances, storage tanks, pipelines, wells, or other pieces of equipment – mostly from industrial activities. In addition to the economic cost of lost commodities, fugitive emissions contribute to local air pollution and may cause further environmental harm. Common industrial gases include refrigerants and natural gas, while less common examples are perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride.
Most occurrences of fugitive emissions are small, of no immediate impact, and difficult to detect. Nevertheless due to rapidly expanding activity, even the most strictly regulated gases have accumulated outside of industrial workings to reach measurable levels globally. Fugitive emissions include many poorly understood pathways by which the most potent and long-lived ozone depleting substances and greenhouse gases enter Earth's atmosphere.
In particular, the build-up of a variety of man-made halogenated gases over the past several decades contributes more than 10% of the radiative forcing which drives global climate change as of year 2020. Moreover, the ongoing banking of small to large quantities of these gases within consumer appliances, industrial systems, and abandoned equipment throughout the world has all but guaranteed their future emissions for many years to come. Fugitive emissions of CFCs and HCFCs from legacy equipment and process uses have continued to hinder recovery of the stratospheric ozone layer in the years since most production was banned in accordance with the international Montreal Protocol.
Similar legacy issues continue to be created at ever-increasing scale with the mining of fossil hydrocarbons, including gas venting and fugitive gas emissions from coal mines, oil wells, and gas wells. Economically depleted mines and wells may be abandoned or poorly sealed, while properly decommissioned facilities may experience emission increases following equipment failures or earth disturbances. Satellite monitoring systems are beginning to be developed and deployed to aid identification of the largest emitters, sometimes known as super-emitters.
In Germany, mining and crushing rock for roadmaking releases as much sulphur into the environment as does airborne emissions, the difference being that in the first case the sulphur will take some time to oxidize to sulphur dioxide.