Volatile Organic Compound Emissions from Humans Indoors

Area of Science:

• Environmental Chemistry
• Indoor Air Quality
• Human Exposure Science

Background:

• Traditional research on indoor airborne chemicals overlooks occupant emissions.
• Occupant emissions significantly contribute to indoor volatile organic compounds (VOCs) and influence indoor chemistry.
• Quantifying human-emitted VOCs is crucial for understanding indoor air quality.

Purpose of the Study:

• To quantify occupant-related gaseous VOC emissions in a university classroom.
• To determine the contribution of human emissions to the overall indoor VOC profile.
• To identify the specific VOCs emitted by occupants.

Main Methods:

• Utilized a proton-transfer-reaction time-of-flight mass spectrometer for real-time VOC measurements.
• Measured time-resolved VOC concentrations in room air and supply air during occupied and unoccupied periods.
• Calculated emission factors by dividing occupant-associated source rates by occupancy.

Main Results:

• Human-emitted VOCs constituted the dominant source (57%) by mass in the occupied classroom.
• Ventilation supply air was the second largest source (35%), with indoor nonoccupant emissions being the least (8%).
• Prominent human-emitted VOCs included those from personal care products, metabolic processes (isoprene, methanol, acetone, acetic acid), and skin oil oxidation (4-OPA, 6-MHO).
• The total occupant-associated VOC emission factor was 6.3 mg h^-1 per person.

Conclusions:

• Occupant emissions are a major determinant of indoor air chemistry and VOC concentrations.
• Personal care products and metabolic processes are significant sources of human-emitted VOCs.
• Effective indoor air quality management must account for direct human contributions.