In order for a flammable gas to explode, there must be enough of the gas in the air, enough oxygen, and a source of ignition. Figures representing the higher and lower limits of the explosive range are expressed in percentages. The amount of oxygen that must be present for an explosion to occur is also expressed as a percentage. The explosive range of methane, for example, is 5 to 15 percent in the presence of at least 12.1 percent oxygen. Solubility is the ability of a gas to be dissolved in water.
Some gases found in mines are soluble and can be released from water.
Sulfur dioxide and hydrogen sulfide, for example, are water-soluble gases. Both may be released from water. Solubility is an important factor to consider during recovery operations. When a mine is sealed off for any length of time, water can collect in it. This water may have occurred naturally, or it may have been introduced during firefighting.