We report the application of an infrared (IR) differential absorption Lidar (DIAL) system (also capable of ultra violet measurements) built at the National Physical Laboratory (NPL), UK, to field measurements of total site emissions (controlled and fugitive) from petrochemical and landfill installations. The validation of the IR-DIAL was carried out via a series of controlled field experiments including comparison to GC analysis and tests against controlled methane releases from a test stack, all detailing agreements on the order of ±20%. In volatile organic compound (VOC) measurements at a UK petrochemical site it was found that the American Petroleum Institute's methodology of the time for calculating the emitted flux underestimated by a factor of 2.4. Also, in a similar field trial it was found that scaling traditional point measurements at easily accessible flanges and valves to represent all flanges and valves on a site led to an underestimation by a factor of 6. In addition to petrochemical examples we also report field measurements from a landfill site to demonstrate the advantageous of the DIAL technique for monitoring area emission sources. In this case study it was found that active (still being filled) cells resulted in significantly greater VOC emission rates (30 kg h(-1)) than closed (≤ 10 kg h(-1)).