Methane click uses a 5 Volt power supply to detect the gas that Alessandro Volta himself discovered in 1776.
Long story short, Alessandro Volta poked the bottom of Lake Maggiore with a stick, observed bubbles rising to the water surface, trapped the gas, set it on fire, and called it "inflammable air from marshlands".
Flash forward a few hundred years and today you'll use a MQ-4 sensor on Methane click to detect the gas in the range from 200 to 10000ppm. The click board also has a potentiometer that allows you to adjust the sensor for the environment you'll be using it in - be it a marshland or some other source closer by.
Generally speaking, there is a lot more methane in the atmosphere than during Volta's time, human activities being a major contributor. Whether it's from agriculture or landfills. It's something to be aware of, because even though methane is not toxic, it's a greenhouse gas.