Most of the explosions in mines occur due to the mixing of

Most underground mine explosions are caused by accumulations of methane (firedamp) mixing with air and encountering an ignition source. Methane–air mixtures are highly flammable and have a well‑known explosive range; mixtures around 9–10% are especially volatile, and methane–air mixtures have been responsible for many coal‑mine disasters [1]. Official mining safety reviews identify methane buildup and ventilation failures as primary causes of mine explosions, and recommend continuous methane monitoring to prevent concentrations reaching dangerous levels [2]. Industry summaries also treat firedamp as predominantly methane and a principal explosive hazard in mines. Thus, “methane with air” is the correct choice.

Sources

1. [1] https://laborcommission.utah.gov/wp-content/uploads/2019/11/Fire-Boss-Study-Guide.pdf
2. [2] https://www.cdc.gov/niosh/mining/topics/fires-explosions.html