Volatile Organic Compound Emissions from Humans Indoors

Abstract

25Research on the sources of indoor airborne chemicals has traditionally focused on outdoor air, 26 building materials, furnishings, and activities such as smoking, cooking and cleaning. Relatively 27 little research has examined the direct role of occupant emissions, even though this source 28 clearly contributes to indoor volatile organic compounds (VOCs) and influences indoor 29 chemistry. In this work, we quantify occupant-related gaseous VOC emissions in a university 30 classroom using a proton-transfer-reaction time-of-flight mass spectrometer. Time-resolved 31 concentrations of VOCs in room air and supply air were measured continuously during occupied 32 and unoccupied periods. The emission factor for each human-emitted VOC was determined by 33 dividing the occupant-associated source rate by the corresponding occupancy. Among the most 34 abundant species detected were compounds associated with personal care products. Also 35 prominent were human metabolic emissions, such as isoprene, methanol, acetone, and acetic 36 acid. Additional sources included human skin oil oxidation by ozone, producing compounds such 37 as 4-oxopentanal (4-OPA) and 6-methyl-5-hepten-2-one (6-MHO). By mass, human-emitted 38VOCs were the dominant source (57%) during occupied periods in a well-ventilated classroom, 39 with ventilation supply air the second most important (35%), and indoor non-occupant emissions 40 the least (8%). The total occupant-associated VOC emission factor was 6.3 mg h -1 per person. 41 42

Indoor ozone/human chemistry and ventilation strategies

“…Equation (1) Equations (3)(4)(5)(6)(7)(8), k shirt , the first-order ozone removal rate coefficient by the t-shirts, was calculated as k shirt = k sur − k chamber = (1.2 ± 0.1) h −1 .…”

How do breath and skin emissions impact indoor air chemistry?

“…So far we have focused on skin and breath emissions, rather than including additional emissions that may arise following the use of personal care products, such as fragrances and body sprays. Tang et al measured mixing ratios of selected VOCs in a university classroom and also the emission rates/person based on these concentrations. The measurements were conducted over a 2‐week period on 5 weekdays (during 08:00‐20:45 hour) when at least 17 adult occupants were present in the classroom.…”

Human symptom responses to bioeffluents, short-chain carbonyls/acids, and long-chain carbonyls in a simulated aircraft cabin environment

“…7, 29, 31 In particular, ozone by-products include creating or modifying carbonyls in the air of indoor settings in addition to the aircraft cabin that can be irritating and cause headaches, general malaise and lower a person’s ability to concentrate, which can be of concern to aircraft passengers. 6, 20, 32–34 While we incorporated several of these carbonyls in our evaluation, many additional compounds can be produced from ozone reactions. If properly maintained ozone scrubbers are not used, ozone levels in the aircraft cabin can be high when the flight paths are at high elevations (>10,000 m) or for planes flying at lower altitudes if stratospheric air penetrates into the troposphere.…”