Time-resolved spectrometry was conducted in the mid-infrared region (2.8-4.6 microm). A galvano-mirror causes a spectrally dispersed beam to repeatedly sweep up and down a PtSi focal plane array so that each element of the array is struck by the beam only once at some point within a time frame. Transient spectra of flowing gases (hydrocarbon and carbon dioxide) were measured at 80 micros intervals.