Inert components in a fuel-air mixture limit the temperature and pressure rise on ignition or prevent ignition completely. Nitrogen is commonly employed as an inert gas. Water vapor and carbon dioxide are somewhat more effective inerting gases due to their higher molar heat capacities. This is evidenced by the effect of these gases on minimum oxygen concentration. For brown coal the LOC is 11,12.4, and 13 vol % when the inert is N2, H2O, or CO2, respectively (Bartknecht 1989). Some metal dusts (e.g., magnesium, titanium, and zirconium), which may react with nitrogen or carbon dioxide, must be inerted using a noble gas such as argon.