At which concentrations can methane in the presence of air become explosive?

Methane can become explosive when it is present in the air within certain concentration limits known as the lower explosive limit (LEL) and upper explosive limit (UEL). For methane, the LEL is approximately 5 percent by volume in air, and the UEL is about 15 percent. When concentrations of methane fall below 5 percent, there is insufficient fuel for combustion, and concentrations above 15 percent create an atmosphere that is too rich in fuel for proper combustion to occur.

Therefore, the correct range of concentrations for methane in the presence of air to create a risk of explosion is indeed between 5 and 15 percent. Understanding these limits is crucial for environmental health specialists and safety professionals when assessing the risk of explosive atmospheres in various settings, such as industrial environments or places where gas appliances are used. Recognizing these thresholds helps in implementing appropriate safety measures and in emergency preparedness planning.