The refrigerant R134a is classified as a greenhouse gas and was banned from use (in vehicles) by the European Union in 2017 due to its contribution to global warming. The more expensive alternative refrigerant R1234yf is considered an environmentally less harmful alternative owing to its significantly lower global warming potential. Our newly developed gas detector can detect both refrigerants separately and, thus, help prevent the use of illegal gas mixtures that contain both refrigerants.