A dual-comb spectroscopy (DCS) based on mid-IR quantum cascade laser combs is a powerful tool for sensitive chemical detection. We have developed an eye-safe DCS spectrometer to perform remote sensing of chemicals in urban environments. The technique utilizes multi-heterodyne down-conversion of QCL optical comb modes from the optical domain to the radio frequency (RF) domain to perform mid-infrared (mid-IR) spectroscopic detection.