Editing Longwall mining (section)

=== Gas emissions ===
Longwall mines have been observed to release [[Methane|methane gas]], a common [[greenhouse gas]] into the environment, however the increase of a typical longwall mine face from {{convert|200|to|300|m}} was not found to release significantly more methane.<ref name=":2">{{Cite web |url=https://www.cdc.gov/niosh/mining/works/coversheet494.html |title=Prediction of Longwall Methane Emissions: An Evaluation of the Influence of Mining Practices on Gas Emissions and Methane Control Systems |website=www.cdc.gov |language=en-us |access-date=2019-04-10}}</ref><ref>{{Cite book |last1=McCall |first1=F. E. |last2=Garcia |first2=F. |last3=Trevits |first3=M. A. |last4=Aul |first4=G. |date=1993-12-31 |title=Methane gas emissions during longwall mining |language=en |osti=143760}}</ref> [[Methane emissions]] from closed longwall mines can continue for up to fifteen years, however it is possible to measure the volume of potential methane emissions based on water flow in the closed mines.<ref name=":2" />