Direct absorption spectroscopy is the ideal method for measuring concentration and chemical composition in a variety of environments. However, it generally requires a very stable light source, such that continuous-wave lasers must be used to achieve high sensitivity. This is unfortunate because pulsed lasers cover a larger portion of the spectrum and are considerably easier to use. The development of cavity ringdown laser absorption spectroscopy (CRLAS) has allowed researchers to use simple pulsed laser technology in direct absorption experiments, achieving sensitivities rivaling that of more complicated continuous-wave techniques.