Emissions of soot, PAHs, ultrafine particles, NOx, and other health relevant compounds from stressed burning of candles in indoor air.

Burning candles release a variety of pollutants to indoor air, some of which are of concern for human health. We studied emissions of particles and gases from the stressed burning of five types of pillar candles with different wax and wick compositions. The stressed burning was introduced by controlled fluctuating air velocities in a 21.6 m3 laboratory chamber. The aerosol physicochemical properties were measured both in well-mixed chamber air and directly above the candle flame with online and offline techniques. All candles showed different emission profiles over time with high repeatability among replicates. The particle mass emissions from stressed burning for all candle types were dominated by soot (black carbon; BC). The wax and wick composition strongly influenced emissions of BC, PM2.5 , and particle-phase polycyclic aromatic hydrocarbons (PAHs), and to lower degree ultrafine particles, inorganic and organic carbon fraction of PM, but did not influence NOx , formaldehyde, and gas-phase PAHs. Measurements directly above the flame showed empirical evidence of short-lived strong emission peaks of soot particles. The results show the importance of including the entire burn time of candles in exposure assessments, as their emissions can vary strongly over time. Preventing stressed burning of candles can reduce exposure to pollutants in indoor air.

Emissions of ultrafine particles from five types of candles during steady burn conditions.

Emissions from candles are of concern for indoor air quality. In this work, five different types of pillar candles were burned under steady burn conditions in a new laboratory scale system for repeatable and controlled comparison of candle emissions (temperature ~25°C, relative humidity ~13%, O2 >18%, air exchange rate 1.9 h-1 ). Burn rate, particle number concentrations, mass concentrations, and mode diameters varied between candle types. Based on the results, the burning period was divided in two phases: initial (0-1 h) and stable (1-6 h). Burn rates were in the range 4.4-7.3 and 4.7-7.1 g/h during initial and stable phase, respectively. Relative particle number emissions, mode diameters, and mass concentrations were higher during the initial phase compared to the stable phase for a majority of the candles. We hypothesize that this is due to elevated emissions of wick additives upon ignition of the candle together with a slightly higher burn rate in the initial phase. Experiments at higher relative humidity (~40%) gave similar results with a tendency toward larger particle sizes at the higher relative humidity. Chemical composition with respect to inorganic salts was similar in the emitted particles (dry conditions) compared to the candlewicks, but with variations between different candles.

Real-time monitoring of lycopene content in tomato-derived products during processing: implementation of a novel double-slit Raman spectrometer.

Lycopene is a very attractive antioxidant associated with cancer prevention in humans. Therefore, it is important to develop new analytical methods that allow for differentiation of food production streams that contain various antioxidant concentrations. The lycopene content in tomato juice, an intermediate between raw tomatoes and the final tomato paste product, was monitored on-line for 46 days at a production plant with a novel, patented double-channel Raman setup. The setup comprises a double-channel mini spectrometer placed in a fixed optical setup, and for each measurement there are two slightly shifted Raman spectra on the x-axis that opens up for additional data processing. The prototype was constructed specifically for 532 nm excitation with no moving parts, and it was designed to optimize each part for the rest of the system. That was the first step toward an integrated optical in-line process analytical solution for industry. As proof of concept, the developed prototype was able to perform a real-time differentiation of the normal and medium to high lycopene content in tomato juice. A correlation factor for double-channel measurements was compared with a correlation factor for background-corrected single-channel measurements by correlating with high performance liquid chromatography reference measurements (1-20 mg of lycopene per 100 g of wet sample). The latter gave a slightly better correlation for the specific application (R(2) = 0.76), acceptable for proof of concept. Real-time information is extremely valuable for the tomato processing plant, mainly because it can be used for improved differentiation of high lycopene content tomato paste to ensure a higher product price. In addition, the developed process analytical technology solution allows for differentiated payment of the tomato farmers based on the lycopene content in their crops.