An emission monitoring system includes at least one gas analyzer for measuring a concentration of a first gas and a concentration of a second gas, a positioning system for determining the location of the at least one gas analyzer when the concentration of the first gas is measured. A method for monitoring emissions at an industrial site and a computer-implemented event detection system applies the steps of detecting the presence of a gas emission event based on a first detection ratio calculated from the measured concentration of the first gas, the measured concentration of the second gas, a background concentration of the first gas and a background concentration of the second gas.