https://www.scientificamerican.com/article/black-inventor-garrett-morgan-saved-countless-lives-with-gas-mask-and-improved-traffic-lights/

Just before midnight at the close of a hot summer day in 1916, a natural gas pocket exploded 120 feet beneath the waves of Lake Erie. It happened during work on Cleveland’s newest waterworks tunnel, a 10-foot-wide underwater artery designed to pull in water from about five miles out, beyond the city’s polluted shoreline. The blast left twisted conduit pipes littering the tunnel floor and tore up railroad tracks inside the corridor, with noxious smoke curling off the rubble. When the dust settled, 11 tunnel workers were dead.

Two rescue parties entered the tunnel searching for survivors. But they lacked proper safety equipment for the smoke and fumes; 11 of the 18 rescuers died. Some 11 hours later, desperate to save anyone still alive, the Cleveland Police turned to Garrett A. Morgan—a local inventor who called himself “the Black Edison”—and the gas mask he had patented two years earlier.