Cavity-enhanced absorption spectroscopy (CEAS) has similarities with the better known cavity ringdown technique (CRDS) which measures the signal decay as a laser pulse emerges through one of the mirrors after successive reflections. By measuring the increase in the rate of decay caused by an absorbing species, CRDS can measure ppb concentrations of small molecules. The ringdown technique has typically been applied to small molecules where the wavelength of a NIR laser source can be tuned across very narrow individual lines of the spectra. In contrast this report describes CEAS using a broadband source applied to larger molecules where the spectra are broader.