Sources of Gas-Phase Species in an Art Museum from Comprehensive Real-Time Measurements

Indoor gases in an art museum were measured by two real-time chemical ionization mass spectrometers (CIMS; iodide (I-CIMS) and nitrate (NO3-CIMS) reagent ions) and a proton-transfer-reaction mass spectrometer (PTR-MS). A positive matrix factorization (PMF) analysis isolated nine different factors capturing the variability. Three factors were observed by all instruments, comprising over 30% of the organic carbon from each instrument. Of these three, one factor correlated with CO2, indicating a clear influence from human occupancy, and another was dominated by small carboxylic acids and was likely related to building materials. The third factor was dominated by HONO and ethylene glycol, with strong emission signatures after gallery painting. Additional factors correlated with ozone (O-3) and nitrogen dioxide and are suggestive of indoor surface reaction products from outdoor-related oxidants. Outdoor-related factors contributed 20% of the measured organic carbon. Organic nitrogen compounds were measured and found to correlate with the estimated nitrate radical (NO3) concentration. The PTR-MS/I-CIMS/NO3-CIMS factors had higher, medium, and lower estimated volatility, respectively, while the carbon oxidation state followed the opposite trend. The majority of the VOC reactivity was due to indoor-related factors (52-77%) for all oxidants except O-3 (44%). Human occupancy increased the reactivity of the human-related (x14), small acid (x1.5), terpene (x2), and acetone (x5) factors. The lifetime of oxidant reactivity (tau(OxR)) against each oxidant for all factors was greater than the museum ventilation time scale, indicating that the reactivity from indoor sources is largely removed outdoors. The dominant VOC fates for all identified sources were ventilation and surface deposition.

Automated summary

Indoor gases in an art museum were analyzed using different instruments, revealing multiple factors affecting the generation of organic carbon. Some factors were related to human occupancy, some to building materials, and others to emissions after painting in the gallery.