A closed-path infrared absorption spectrometer was outfitted with the option for active continuous passivation for measuring large, rapid gradients in atmospheric NH₃ from a research aircraft. In-flight and ground observations show utility in passivant addition for recovering instrument time response when sampling surfaces are contaminated and cannot be cleaned in a timely manner and for maintaining rapid time response in an NH₃-rich and humid environment over a several-week-long field campaign.