文摘
We used proton-transfer-reaction mass spectrometry(PTR-MS) to examine the products formed when ozonereacted with the materials in a simulated aircraft cabin,including a loaded high-efficiency particulate air (HEPA)filter in the return air system. Four conditions wereexamined: cabin (baseline), cabin plus ozone, cabin plussoiled T-shirts (surrogates for human occupants), and cabinplus soiled T-shirts plus ozone. The addition of ozone tothe cabin without T-shirts, at concentrations typicallyencountered during commercial air travel, increased themixing ratio (v:v concentration) of detected pollutants from35 ppb to 80 ppb. Most of this increase was due to theproduction of saturated and unsaturated aldehydes andtentatively 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 aironly slightly, whereas the combination of soiled T-shirts andozone increased the mixing ratio of detected pollutantsto 110 ppb, with more than 20 ppb originating from squaleneoxidation products (acetone, 4-oxopentanal, and 6-methyl-5-hepten-2-one). For the two conditions with ozonepresent, the more-abundant oxidation products includedacetone/propanal (8-20 ppb), formaldehyde (8-10ppb), nonanal (~6 ppb), 4-oxopentanal (3-7 ppb), aceticacid (~7 ppb), formic acid (~3 ppb), and 6-methyl-5-hepten-2-one (0.5-2.5 ppb), as well as compounds tentativelyidentified as acrolein (0.6-1 ppb) and crotonaldehyde (0.6-0.8 ppb). The odor thresholds of certain products wereexceeded. With an outdoor air exchange of 3 h-1 and arecirculation rate of 20 h-1, the measured ozone surfaceremoval rate constant was 6.3 h-1 when T-shirts werenot present, compared to 11.4 h-1 when T-shirts werepresent.
