A respiratory monitor is disclosed that includes features for conducting multiple pulmonary function tests in a single device and for detecting the presence of nitric oxide in exhaled breath. The respiratory monitor includes one or more reactor and sensor assemblies. Also described is a mouthpiece that allows for separate inhalation and exhalation pathways and for filtering inhaled and exhaled breath for predetermined species prior to exhalation into the respiratory monitor. The monitor further allows for wired, wireless and network connectivity and for cloud-based systems for communicating and correlating pulmonary data as well as relevant environmental data and displaying the data for use by patients and health care professionals.