This is correct. A person in a hermetically sealed suit will die of CO2 poisoning a long time before Oxygen deprivation. However in most mines, they will engine

This is correct. A person in a hermetically sealed suit will die of CO2 poisoning a long time before Oxygen deprivation. However in most mines, they will engineer gas permeability so that CO2 and other poisonous gasses can seep to areas with lower concentrations and out of the mine. Coal mines seem to be particularly bad with regards to permeability. In this case, an Oxygen candle _MAY_ be enough to keep people alive. However, why O2 tanks would need scrubbers and candles wouldn't doesn't make any sense. https://www.hindawi.com/journals/ace/2018/3976505/ https://www.hindawi.com/journals/ace/2018/3976505/ https://www.cdc.gov/niosh/mining/works/coversheet1621.html https://www.cdc.gov/niosh/mining/works/coversheet1621.html