Occupant generated carbon dioxide as a measure of dilution ventilation efficiency

Area of Science:

• Environmental Science
• Building Science
• Occupational Health

Background:

• Indoor air quality (IAQ) is crucial for occupant health and productivity.
• Traditional ventilation assessment methods can be complex and time-consuming.
• Occupant-generated carbon dioxide (CO2) as a tracer gas offers a potential screening tool.

Purpose of the Study:

• To evaluate the efficacy of a carbon dioxide (CO2) decay model for indoor air quality screening.
• To determine if CO2 decay can accurately estimate ventilation rates and effectiveness.
• To correlate CO2-derived ventilation metrics with qualitative assessments.

Main Methods:

• Utilized a dilution chamber to test an exponential decay model for CO2.
• Collected data on CO2 concentration changes over time after simulated occupancy.
• Calculated air changes per unit time, effective ventilation rate, and ventilation effectiveness.
• Correlated model-derived metrics with qualitative ventilation assessments in office and lab settings.

Main Results:

• The limited exponential decay model demonstrated a good fit with chamber test data.
• Correlation coefficients for log-linear plots approached unity, indicating model reliability.
• Ratios of actual to calculated airflow were close to unity.
• CO2-measured air changes positively correlated with qualitative ventilation effectiveness assessments.

Conclusions:

• Carbon dioxide (CO2) decay is a viable method for indoor air quality screening.
• The CO2 decay model accurately estimates ventilation rates and effectiveness.
• This approach provides a reliable, non-invasive method for assessing building ventilation performance.