His medical interest led him to investigate the gases the miners breathed – fire damp (methane) and choke damp (oxygen depleted air). Carlisle Spedding helped to build a laboratory for Brownrigg and fed it with gases from a nearby coal mine through lead pipes. Brownrigg developed methods of collecting and transferring the gases and supplied James Lowther with gas filled bladders to show to The Royal Society which then elected Brownrigg as a Fellow.
His experiments on gases continued and after visiting a spa resort in Germany he became interested in gases to be found in mineral waters. A paper he published entitled "Experimental inquiry concerning the nature of the mineral elastic spirit or air contained in the Pouhon water, and other acidulae" earned him the prestigious Copley Medal in 1766.