IndoorChem

While little is known about the chemistry of the indoor atmosphere, a surprising diversity of organic molecules are present. This diversity includes structural isomers – molecules with shared elemental composition – i.e. same number of carbon, hydrogen, oxygen, etc. atoms – but with different arrangements of those atoms. These structural and subsequent energetic differences of the molecules affect their capacity to participate in chemical reactions. For example, limonene has two double bonds, while alpha-pinene has only one – the resulting oxidation kinetics and SOA yields of these two monoterpenes (C₁₀H₁₆) upon reaction with NO₃, OH or O₃ are thus different. However, fast, sensitive and quantitative measurements of isomeric structures are not currently available. We aim to develop a mass spectrometer that will isomerically resolve and quantify molecules by taking advantage of differences in the thermodynamics of ion-molecule reactions in chemical ionization mass spectrometers. Coupled with chemical ionization and calibrations of target species, this approach aims to provide a broadly applicable technique of resolving organic isomers in the indoor environment. We will test the instrument in a field project focused on investigating links between indoor air composition and infiltration. The residence-based measurement campaign is designed to address two scientific knowledge gaps: 1) how chemical properties of gases (and particles) change as they infiltrate across the residential built environmental envelope, and 2) how organic molecules in outdoor air contribute to the composition of indoor air.