title: Products of ozone-initiated chemistry in a simulated aircraft environment.
abstract: We used proton-transfer-reaction mass spectrometry (PTR-MS) to examine the products formed when ozone reacted with the materials in a simulated aircraft cabin, including a loaded high-efficiency particulate air (HEPA) filter in the return air system. Four conditions were examined: cabin (baseline), cabin plus ozone, cabin plus soiled T-shirts (surrogates for human occupants), and cabin plus soiled T-shirts plus ozone. The addition of ozone to the cabin without T-shirts, at concentrations typically encountered during commercial air travel, increased the mixing ratio (v:v concentration) of detected pollutants from 35 ppb to 80 ppb. Most of this increase was due to the production of saturated and unsaturated aldehydes and tentatively identified low-molecular-weight carboxylic acids. The addition of soiled T-shirts, with no ozone present, increased the mixing ratio of pollutants in the cabin air only slightly, whereas the combination of soiled T-shirts and ozone increased the mixing ratio of detected pollutants to 110 ppb, with more than 20 ppb originating from squalene oxidation products (acetone, 4-oxopentanal, and 6-methyl-5-hepten-2-one). For the two conditions with ozone present, the more-abundant oxidation products included acetone/propanal (8-20 ppb), formaldehyde (8-10 ppb), nonanal (approximately 6 ppb), 4-oxopentanal (3-7 ppb), acetic acid (approximately 7 ppb), formic acid (approximately 3 ppb), and 6-methyl-5-hepten-2-one (0.5-2.5 ppb), as well as compounds tentatively identified as acrolein (0.6-1 ppb) and crotonaldehyde (0.6-0.8 ppb). The odor thresholds of certain products were exceeded. With an outdoor air exchange of 3 h(-1) and a recirculation rate of 20 h(-1), the measured ozone surface removal rate constant was 6.3 h(-1) when T-shirts were not present, compared to 11.4 h(-1) when T-shirts were present.
authors.affiliation: International Centre for Indoor Environment and Energy, Technical University of Denmark (DTU), DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Armin
authors.initials: A
authors.lastname: Wisthaler
authors.forename: Gyöngyi
authors.initials: G
authors.lastname: Tamás
authors.forename: David P
authors.initials: DP
authors.lastname: Wyon
authors.forename: Peter
authors.initials: P
authors.lastname: Strøm-Tejsen
authors.forename: David
authors.initials: D
authors.lastname: Space
authors.forename: Jonathan
authors.initials: J
authors.lastname: Beauchamp
authors.forename: Armin
authors.initials: A
authors.lastname: Hansel
authors.forename: Tilmann D
authors.initials: TD
authors.lastname: Märk
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Weschler
mesh_terms: D016902:Air Pollution, Indoor / Q000032:analysis* / Q000517:prevention & control*; D000401:Aircraft; D003020:Clothing; D005374:Filtration; D013058:Mass Spectrometry; D008422:Materials Testing; D008962:Models, Theoretical; D009930:Organic Chemicals; D010083:Oxidants, Photochemical / Q000737:chemistry*; D010084:Oxidation-Reduction; D010126:Ozone / Q000737:chemistry*
chemical_list: D009930:Organic Chemicals; D010083:Oxidants, Photochemical; D010126:Ozone