Based on cavity ringdown spectroscopy technology, the ESP-1000 unveiled by Picarro Inc. is an ultrasensitive instrument for the measurement of trace gas. Applications include semiconductor manufacturing, petrochemical refining, environmental monitoring and diesel emissions analysis. It achieves parts-per-billion sensitivity without extensive sample preparation or user interaction, and it operates in the field. Proprietary control of wavelength, temperature and pressure, as well as spectral analysis algorithms produce accurate measurements that are stable over long periods. The device is factory-configured according to application. Sensitivity, speed and specificity are investigated using spectral databases in the near-IR. Performance characteristics are evaluated, and key components, such as laser, mirror and coatings, are selected based upon the application.