VOCs and particles are emitted when incense and candles are burned. Candles were put in a test chamber and used a high sensitivity-proton transfer reaction-mass spectrometer (HS-PTR-MS) and a condensation particle counter (CPC). As expected, the concentration peaked immediately after the burning period and decayed until returning to the initial concentration levels. The concentration levels and the time of decay were greatly influenced by the ventilation and surface interactions. The study found a high correlation between the decay rate constant of the VOCs and the physiochemical properties including the molecular weight, melting point, boiling point, molecular volume, refractive index, density, solubility in water, and the vapor pressure. During combustion, the emissions of particles peaked at 22.0(+/-0.2) x 10^4 particles/cm^-3 for candles and incenses.

The study states that, “The performed kinetic measurements highlight the temporal evolution of the exposure level and reveal the importance of ventilation and deposition to remove the particles in a few hours in indoor environments” (Manoukian 2013). This is interesting because people purposely emit these particles and VOCs by lighting candles when really, they must get rid of the particles immediately after; it’s very contradictory. Inhalation of these particles contribute to acute and chronic health effects such as damage to the nervous system, immune and reproductive diseases, developmental problems, cancers, and respiratory system dysfunction (WHO 2005). Many studies have been carried out to characterize the VOC and particle emissions, however very few of them determine the concentration and its correlation to time after emission. This study aimed to tackle this interest.

The parameters for the study included:

• Controlled incense and candles with no dye and all specimens were used from the same supplier batch.
• Experiments carried out in the “Mechanized house for Advanced Research on Indoor Air (MARIA).
• The chamber where the specimens were tested was 2.53×5.15m with a volume of 32.3 m^3.
• The ceiling was painted concrete, and the walls had patched of painted plaster.
• No furniture was present in the chamber besides a support set for the candles and incense placed 1m above the floor level.
• Ventilation in the chamber was controlled by a mechanical exhaust system at the bottom of the door. The device drew air our of the chamber and brought in outdoor air through a hole above the window on the opposite wall.
• Ventilation constant at 25.8m^3 h^-1.
• Air exchange rate = 0.80 (+/- 0.08) h^-1
• Temperature = 16.2 (+/-0.4) °C 
• Relative humidity = 50 (+/-6)%

Measurements were taken in a “mass scan” mode on a mass spectrum between 20 and 270 amu at a mass detection rate of 1 s amu^-1. The HS-PTR-MS provides concentration-time stamps of 4 minutes. A CPC set at a flow rate of 0.31min^-1 was used to measure the number of particles

VOCs and particles are emitted when incense and candles are burned. Candles were put in a test chamber and used a high sensitivity-proton transfer reaction-mass spectrometer (HS-PTR-MS) and a condensation particle counter (CPC). As expected, the concentration peaked immediately after the burning period and decayed until returning to the initial concentration levels. The concentration levels and the time of decay were greatly influenced by the ventilation and surface interactions. The study found a high correlation between the decay rate constant of the VOCs and the physicochemical properties including the molecular weight, melting point, boiling point, molecular volume, refractive index, density, solubility in water, and the vapor pressure. During combustion, the emissions of particles peaked at 22.0(+/-0.2) x 10^4 particles/cm^-3 for candles and incense.

The study states that, “The performed kinetic measurements highlight the temporal evolution of the exposure level and reveal the importance of ventilation and deposition to remove the particles in a few hours in indoor environments” (Manoukian 2013). This is interesting because people purposely emit these particles and VOCs by lighting candles when really, they must get rid of the particles immediately after; it’s very contradictory. Inhalation of these particles contribute to acute and chronic health effects such as damage to the nervous system, immune and reproductive diseases, developmental problems, cancers, and respiratory system dysfunction (WHO 2005). Many studies have been carried out to characterize the VOC and particle emissions, however very few of them determine the concentration and its correlation to time after emission. This study aimed to tackle this interest.

The parameters for the study included:

• Controlled incense and candles with no dye and all specimens were used from the same supplier batch.
• Experiments carried out in the “Mechanized house for Advanced Research on Indoor Air (MARIA).
• The chamber where the specimens were tested was 2.53×5.15m with a volume of 32.3 m^3.
• The ceiling was painted concrete, and the walls had patches of painted plaster.
• No furniture was present in the chamber besides a support set for the candles and incense placed 1m above the floor level.
• Ventilation in the chamber was controlled by a mechanical exhaust system at the bottom of the door. The device drew air out of the chamber and brought in outdoor air through a hole above the window on the opposite wall.
• Ventilation constant at 25.8m^3 h^-1.
• Air exchange rate = 0.80 (+/- 0.08) h^-1
• Temperature = 16.2 (+/-0.4) °C 
• Relative humidity = 50 (+/-6)%

Measurements were taken in a “mass scan” mode on a mass spectrum between 20 and 270 amu at a mass detection rate of 1 s amu^-1. The HS-PTR-MS provides concentration-time stamps of 4 minutes. A CPC set at a flow rate of 0.31min^-1 was used to measure the number of particles. in diameters from 0.004 to 3 μm.

The results for the concentration over time during and after incense burning are as follows.

The calculated emission rate constant ranged between 92 and 4910 μg h−1. The elimination rate constants k obs were close to 0.80 (+/-0.08)h−1. It was found that, under ventilated conditions, concentrations of pollutants in the gas phase decrease quickly to background levels right after combustion (Lung et al. 2003, Gilbert et al. 2008). Concerning the physicochemical properties and how they influenced the concentration over time, when the vapor pressure increased, and compounds were more volatile, the adsorption/desorption ratio decreased. After the elimination rate constant k obs was close to the air exchange rate, the adsorption was nearly negligible. For the boiling point, the opposite result presented itself. High molecular weight yielded a high elimination rate k obs .

For the number of particles for incense and candle burning concentration over time, the following chart was produced.

The dashed line indicates the combustion start, the broken line indicates the end of the incense burning, and the dotted line indicates the end of the candle burning.

To conclude, the study shows that the combustion of incense and candles is a source of many different types of VOCs and particles indoors. It is no surprise that the number of particles and amount of VOCs increase until combustion is over, and then decays. The concentration of compounds emitted by candles are small, but the substances emitted from incense sticks contain carcinogenic compounds such as formaldehyde and benzene. According to the data and generated charts, the concentration decreases after a few hours when combustion ceases. This can be attributed to the ventilation and adsorption of VOCs and ventilation and deposition of particles. If the room is properly ventilated, candles and incense do not pose a significant threat to the indoor air quality.

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