Emission Characterization of Synthetic and Natural Candles in a Residential Environment

The combustion of candles is known to emit various air pollutants, including particulate matter (PM) and volatile organic compounds (VOCs), into the air. This study characterizes emissions of these pollutants from natural and synthetic candles in a standard, sealed, unventilated residential environment. In addition, computational fluid dynamics (CFD) modeling was used to study the potential effects of inlet air velocity on a paraffin candle flame. A laminar diffusion flame model simulated the distributions of temperature, CO2, and H2O. A Testo DiSC mini air sampler was used for ultrafine particles and Lung-Deposited Surface Area (LDSA) data collection, and a CEM DT-9881 sampler was used for recording larger particle number concentrations, temperature, and relative humidity. VOC sorbent tubes were used for the collection of individual and total VOCs. Study findings showed that natural candles produced significantly (p < 0.05) higher LDSA ranges (mean 195.2 µm2/cm3) and ultrafine particle concentrations (mean 8.4 × 1011 No/m3), while paraffin wax synthetic candles exhibited higher 0.3–10 µm PM concentrations (mean 2.0 × 107 No/m3). CFD modeling showed that increasing air velocity produced a shorter, more compact flame and reduced CO2 and H2O mass fractions due to enhanced mixing and aerodynamic dilution, highlighting the strong interaction between airflow, temperature, and product formation in laminar paraffin flames.