High sensitivities well below 1 ppb can be reached with gas chromatography techniques, but the measurements can be time consuming and the best performance often requires offline or offsite analysis with a separate sampling step. Optical methods based on spectroscopic detection are an appealing alternative. Optical spectrometers are often more compact and more readily develop into fieldcapable instruments and autonomous onsite detectors for continuous monitoring. Some chemical sensors, such as metal oxide sensors, photoionization detectors and electrochemical sensors, are starting to reach high sensitivities for benzene, but spectroscopic detectors offer better selectivity and long-term stability.