Mine fires were initially fought with high expansion foams, filling the galleries with foam asphyxiating the fire when displacing the oxygen. These foams had a very low quantity of water per liter of foam, therefore its cooling effect was not big enough.
Some additives can be used (20% mixing ratio) that contain fireproofing salts and wetting agents that help avoiding the inflammation risk in coal mines.
Another advantageous solution is to use fluorine free additives (very concentrate) that can be used with mixing ratios as low as 0.3% in CAFS, so they produce very compact foams providing great safety against fires in these scenarios.
For the big trucks used in strip mining, the automatic extinguishing systems based in fluorine free foam solutions provide a safer environment for mineral extraction processes.