Determination of the emission indices for NO,NO2, HONO,HCHO, CO,and particles emitted from candles

In the present study, emission indices for NO, NO₂, HONO, HCHO, CO, particle mass, and particle numbers including particle size distributions for three different offering candles were determined. The candles investigated showed similar emission characteristics with emission indices (g/kg) in good agreement with former candle emission studies. An average HONO/NO_x emission ratio of 6.6 ± 1.1% was obtained, which is much higher compared to most other combustion sources, indicating that candles may be a significant indoor source of this important trace gas. The particle size distributions indicate that the majority of the emitted particles are in the size range 7 - 15 nm. Three modes were observed during burning the candles with very different emission profiles: a “normal burning” mode characterized by low particle number emission rates and small particles; an initial “sooting” behavior after ignition, and a final “smoldering” phase upon candle extinction with higher particle number emission rates and larger particles. The particle emission upon extinction is dependent on the extinction method. The NO_x emission indices were applied in a simple box model to calculate typical indoor NO_x concentration levels from candle emissions, which were in excellent agreement with direct measurements in a typical indoor environment.     

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.     

Lead in candle emissions

The candle-using public should be made aware that the core of candle wicks may contain lead. Used as a stiffening agent to keep the wick out of the molten wax, lead can be emitted as particulates to the air and then deposited on indoor surfaces. To define the problem, 100 sets of candles (two or more identical candles) were purchased locally. The criterion for purchase was that the candles must appear to contain a metal-cored wick or be covered by a metallic pigment. Of the candles purchased, 8% contained lead wicks. The wicks were 39-74% lead (the remainder was fabric or paper) and the lead cores (approx. 100% lead) had linear densities of 13-27 mg/cm. Candles were burned to completion in a closed chamber to capture the air emissions, and the candle residue was extracted to assess the lead mass balance. It was found that individual candles emitted lead to the air at average rates that ranged from 100 to 1700 microg/h. Assuming realistic indoor conditions, these emission rates were modeled to project room air concentration, child exposure by inhalation, and indoor deposition. Results showed that burning single candles can easily raise the source room concentration above the ambient air lead concentration limit of 1.5 microg/m3 set by EPA. Burning multiple candles can elevate it above OSHA permissible exposure limits of 50 microg/m3. Although blood lead levels have dropped precipitously in the United States since lead was phased out of gasoline in 1986, nearly 900,000 children still had levels above 10 microg/dl during NHANES III. Considering that candle sales in the US are estimated at $1-2 billion per year, and that children may spend as much as 88% of their time indoors, it is reasonable to suspect that some blood lead elevation in children arises from indoor micro-environments where lead-wick candles are burned.     

Characterization of Flaring and Non-Flaring Container Filled Votive Candles

Authors were provided two sets of 24 exemplar candles. Of these, 24 were identified as the same that the provider had observed “flaring”. Fourier Transform Infrared Spectroscopy (FTIR) analysis of the material showed that the candles that did not flare were soy based wax and that those that did flare were petroleum based wax. Burning the candles showed that melted wax in some petroleum based candles was ignited by the wick flame and produced a pool fire inside the candles’ glass container. Based on measured mass loss rate and the heat of combustion of petroleum based wax, the calculated power output of a normal burning candle is ca. 30 W. When the liquid wax pool ignited, the output was ca. 230 W, with significant flame extension above the top edge of candle’s glass container. The FTIR analysis also showed that twelve of the petroleum based wax candles had a simple hydroxyl compound, likely an alcohol, peak that was not present in the second sample of one dozen petroleum based wax candles. Burn testing showed that the candles from the sample with hydroxyl ignite a pool fire after burning for 15 to 30 min; the second sample of petroleum based wax candles, those that did not have the hydroxyl compound, did not ignite a pool fire. This suggests that the hydroxyl compound reduces the flashpoint of the wax to an ignition temperature attained after burning the candle for tens of minutes. Once the hydroxyl compound petroleum based wax melts and reaches a temperature above its flashpoint/flame point, it vaporizes sufficiently to be ignited, with flame extension of 152 mm (6 in) or more above the wax pool. This flame extension or “flaring” represents a significant fire hazard in that it may ignite nearby combustibles or fracture the candle’s glass container and release burning wax.     

Real-time molecular characterization of air pollutants in a Hong Kong residence: Implication of indoor source emissions and heterogeneous chemistry

Due to the high health risks associated with indoor air pollutants and long-term exposure, indoor air quality has received increasing attention. In this study, we put emphasis on the molecular composition, source emissions, and chemical aging of air pollutants in a residence with designed activities mimicking ordinary Hong Kong homes. More than 150 air pollutants were detected at molecular level, 87 of which were quantified at a time resolution of not less than 1 hour. The indoor-to-outdoor ratios were higher than 1 for most of the primary air pollutants, due to emissions of indoor activities and indoor backgrounds (especially for aldehydes). In contrast, many secondary air pollutants exhibited higher concentrations in outdoor air. Painting ranked first in aldehyde emissions, which also caused great enhancement of aromatics. Incense burning had the highest emissions of particle-phase organics, with vanillic acid and syringic acid as markers. The other noteworthy fingerprints enabled by online measurements included linoleic acid, cholesterol, and oleic acid for cooking, 2,5-dimethylfuran, stigmasterol, iso-/anteiso-alkanes, and fructose isomers for smoking, C₂₈-C₃₄ even n-alkanes for candle burning, and monoterpenes for the use of air freshener, cleaning agents, and camphor oil. We showed clear evidence of chemical aging of cooking emissions, giving a hint of indoor heterogeneous chemistry. This study highlights the value of organic molecules measured at high time resolutions in enhancing our knowledge on indoor air quality.     

Emissions of lead and zinc from candles with metal-core wicks

We measured the amount of lead released from 14 different brands of candles with metal-core wicks sold in Michigan. The emissions of lead were found to range from 0.5 to 66 microg/h, and the rates for zinc were from 1.2 to 124 microg/h. It is estimated that burning four of the candles bought in Michigan for 2 h can result in airborne lead concentrations that can pose a threat to human health. In addition to inhalation of lead in the air, children get exposed to lead in candle fumes deposited on the floor, furniture and walls through their hand-to-mouth activity. Burning candles with leaded-core wick may be an important exposure route for lead that has generally been ignored.     

Characterization of indoor sources of fine and ultrafine particles: a study conducted in a full-scale chamber

Humans and their activities are known to generate considerable amounts of particulate matter indoors. Some of the activities are cooking, smoking and cleaning. In this study 13 different particle sources were for the first time examined in a 32 m3 full-scale chamber with an air change rate of 1.7 +/- 0.1/h. Two different instruments, a condensation particle counter (CPC) and an optical particle counter (OPC) were used to quantitatively determine ultrafine and fine particle emissions, respectively. The CPC measures particles from 0.02 microm to larger than 1.0 microm. The OPC was adjusted to measure particle concentrations in eight fractions between 0.3 and 1.0 microm. The sources were cigarette side-stream smoke, pure wax candles, scented candles, a vacuum cleaner, an air-freshener spray, a flat iron (with and without steam) on a cotton sheet, electric radiators, an electric stove, a gas stove, and frying meat. The cigarette burning, frying meat, air freshener spray and gas stove showed a particle size distribution that changed over time towards larger particles. In most of the experiments the maximum concentration was reached within a few minutes. Typically, the increase of the particle concentration immediately after activation of the source was more rapid than the decay of the concentration observed after deactivation of the source. The highest observed concentration of ultrafine particles was approximately 241,000 particles/cm3 and originated from the combustion of pure wax candles. The weakest generation of ultrafine particles (1.17 x 10(7) particles per second) was observed when ironing without steam on a cotton sheet, which resulted in a concentration of 550 particles/cm3 in the chamber air. The highest generation rate (1.47 x 10(10) particles per second) was observed in the radiator test. PRACTICAL IMPLICATIONS: Humans and their activities are known to generate substantial amounts of particulate matter indoors and potentially they can have a strong influence on short-term exposure. In this study a quantitative determination of the emissions of fine and ultrafine particles from different indoor sources was performed. The aim is a better understanding of the origin and fate of indoor particles. The results may be useful for Indoor Air Quality models.     

Acute health effects from exposure to indoor ultrafine particles—A randomized controlled crossover study among young mild asthmatics

Particulate matter is linked to adverse health effects, however, little is known about health effects of particles emitted from typical indoor sources. We examined acute health effects of short-term exposure to emissions from cooking and candles among asthmatics. In a randomized controlled double-blinded crossover study, 36 young non-smoking asthmatics attended three exposure sessions lasting 5 h: (a) air mixed with emissions from cooking (fine particle mass concentration): (PM_2.5: 96.1 μg/m³), (b) air mixed with emissions from candles (PM_2.5: 89.8 μg/m³), and c) clean filtered air (PM_2.5: 5.8 μg/m³). Health effects (spirometry, fractional exhaled Nitric Oxide [FeNO], nasal volume and self-reported symptoms) were evaluated before exposure start, then 5 and 24 h after. During exposures volatile organic compounds (VOCs), particle size distributions, number concentrations and optical properties were measured. Generally, no statistically significant changes were observed in spirometry, FeNO, or nasal volume comparing cooking and candle exposures to clean air. In males, nasal volume and FeNO decreased after exposure to cooking and candles, respectively. Participants reported additional and more pronounced symptoms during exposure to cooking and candles compared to clean air. The results indicate that emissions from cooking and candles exert mild inflammation in asthmatic males and decrease comfort among asthmatic males and females.     

Wood stove use and other determinants of personal and indoor exposures to particulate air pollution and ozone among elderly persons in a Northern Suburb

A six‐month winter‐spring study was conducted in a suburb of the northern European city of Kuopio, Finland, to identify and quantify factors determining daily personal exposure and home indoor levels of fine particulate matter (PM_2.5, diameter <2.5 µm) and its light absorption coefficient (PM_2.5abs), a proxy for combustion‐derived black carbon. Moreover, determinants of home indoor ozone (O₃) concentration were examined. Local central site outdoor, home indoor, and personal daily levels of pollutants were monitored in this suburb among 37 elderly residents. Outdoor concentrations of the pollutants were significant determinants of their levels in home indoor air and personal exposures. Natural ventilation in the detached and row houses increased personal exposure to PM_2.5, but not to PM_2.5abs, when compared with mechanical ventilation. Only cooking out of the recorded household activities increased indoor PM_2.5. The use of a wood stove room heater or wood‐fired sauna stove was associated with elevated concentrations of personal PM_2.5 and PM_2.5abs, and indoor PM_2.5abs. Candle burning increased daily indoor and personal PM_2.5abs, and it was also a determinant of indoor ozone level. In conclusion, relatively short‐lasting wood and candle burning of a few hours increased residents’ daily exposure to potentially hazardous, combustion‐derived carbonaceous particulate matter.     

Polycyclic aromatic hydrocarbons: levels and phase distributions in preschool microenvironment

This work aims to characterize levels and phase distribution of polycyclic aromatic hydrocarbons (PAHs) in indoor air of preschool environment and to assess the impact of outdoor PAH emissions to indoor environment. Gaseous and particulate (PM₁ and PM_2.5) PAHs (16 USEPA priority pollutants, plus dibenzo[a,l]pyrene, and benzo[j]fluoranthene) were concurrently sampled indoors and outdoors in one urban preschool located in north of Portugal for 35 days. The total concentration of 18 PAHs (ΣPAHs) in indoor air ranged from 19.5 to 82.0 ng/m³; gaseous compounds (range of 14.1–66.1 ng/m³) accounted for 85% ΣPAHs. Particulate PAHs (range 0.7–15.9 ng/m³) were predominantly associated with PM₁ (76% particulate ΣPAHs) with 5‐ring PAHs being the most abundant. Mean indoor/outdoor ratios (I/O) of individual PAHs indicated that outdoor emissions significantly contributed to PAH indoors; emissions from motor vehicles and fuel burning were the major sources.     

Exposure to fine,ultrafine particles and black carbon in two preschools in nur-sultan city of kazakhstan

Children in preschools were studied as an exceptionally vulnerable group to lung diseases due to their immature immune system. Few data are available in the literature addressing the exposure of children in preschools to ultrafine (>10 nm) particles. Exposure of children to fine, ultrafine (10 nm–1 µm) particles and black carbon particles present inside and near two preschools in Nur-Sultan, Kazakhstan, during Fall 2019 was investigated. For Preschool I, the average daily (6 h) indoor (outdoor) PM₁, PM_2.5, and PM₁₀ concentrations over three-week measurements were 15.0 (SD 12.5) µg/m³, 34.6 (SD 35.1) µg/m³, and 47.2 (SD 45.2) µg/m³, respectively. Average indoor UFP concentrations (>10.0 nm) including candle burning events were 5.20 × 10³ (SD 8.80 × 10³) particles/cm³, with the background UFP concentration to be 3.30 × 10³ (SD 1.80 × 10³) particles/cm³. In Preschool II, the average UFP concentration (>30.0 nm) in the morning and afternoon was 3.94 × 10³ (SD 5.34 × 10²) and 3.36 × 10³ (SD 1.90 × 10³) particles/cm³, respectively. Indoor black carbon (BC) concentrations were correlated with the outdoor smoking activity. The major sources of the indoor particles in the preschools were dust resuspension, candle burning, and infiltrated outdoor particles.     

Particle‐associated polycyclic aromatic hydrocarbons in a representative urban location (indoor‐outdoor) from South Europe: Assessment of potential sources and cancer risk to humans

PM₁₀‐bound polycyclic aromatic hydrocarbons (PAHs) levels were monitored at urban locations (outdoor/indoor) within the city of Madrid between May 2017 and April 2018. Fourteen PAH congeners were measured, potential emission sources were identified as were potential carcinogenic risks. The ΣPAHs averaged 0.577 and 0.186 ng/m³ in outdoor and indoor air, with a high linear correlation per individual mean PAH and month. The largest contributors to the ΣPAHs were the high‐molecular‐weight PAHs. Principal component analysis‐multiple linear regression results showed that emissions from diesel and vehicular processes explained 27% and 23% of the total variance of outdoor and indoor air, while combustion processes accounted for 30% and 25% in ambient and indoor air, respectively. During the cold season, biomass burning plus coal and wood combustion were additional sources of outdoor emissions. The heavy‐, medium‐ and light‐molecular‐weight PAH originating from outdoor sources accounted for 72%, 80%, and ~60% of the indoor levels of the three respective PAH groups. Average BaP concentration was 0.029 and 0.016 ng/m³ in outdoor and indoor air, respectively. Estimated BaPeq concentration averaged 0.072, 0.035, and 0.027 ng/m³ for outdoor, indoor, and indoor‐generated individual PAH concentrations, respectively. The estimated carcinogenic risk falls within the range of acceptable risk targeted by the US‐EPA.     

A survey on energy consumption in rural households in the fringes of Xian city

A survey, in the form of a questionnaire, of energy consumption patterns in residential households in the rural fringe of Xian city was undertaken during the winter of 2003/2004. More than 200 households were sampled during the survey. The status of fuel consumption, including the use of biomass fuels for cooking and space heating, was investigated. The types of stoves, purpose of the stove use, and characteristics of the residential houses and residents were also reported and analyzed.The purpose of the survey was to clarify the status of energy consumption and to estimate emissions of greenhouse gases and air pollutants in rural areas of China, from the environmental perspective of climate change and indoor to continental scale air pollution. In rural areas of China, biomass (wood and agricultural waste, such as stalks, corn canes and twigs, branches of wood) is the type of fuel most commonly used. It emits several air pollutants: particulate matter (PM), CO, NMHCs, CH₄ and high levels of black carbon (BC) – a greenhouse effect aerosol, and organic carbon (OC) – a cooling effect aerosol. However, CO₂ emissions from biomass burning are assumed to be zero because of carbon neutrality.From this survey it would then be possible to analyze the fundamentals of emission reduction potential, for air pollutants and greenhouse gases, from the rural household sector in China.     

Emissions of air pollutants from Chinese cooking: A literature review

Cooking can release high concentrations of different air pollutants indoors, including particulate matter, polycyclic aromatic hydrocarbons (PAHs), and other gaseous pollutants such as volatile organic compounds (VOCs), oxides of carbon (CO_x), and oxides of nitrogen (NO_x). Although some reviews have been conducted on emissions from cooking, they have not paid specific attention to Chinese cooking. Subsequent research, however, has focused on this aspect. We collected literature from 1995 to 2016 and summarized air pollutant emissions from Chinese cooking. We analyzed the characteristics of such pollutants based on different influential factors. It was found that the cooking method could have a predominant impact on emissions from Chinese cooking, and oil-based cooking produces air pollutants at much higher levels than water-based cooking. In addition, the use of gas stoves released more pollutants than electric stoves. Furthermore, the type and temperature of oil could have caused disparity in source strengths from the oil heating process. Ventilation patterns or the operation mode of range hoods could control indoor pollution levels. With more information focused on Chinese cooking emissions, we can propose more effective strategies for improving the indoor air environment in China.     

A review of physics and correlations of pool fire behaviour in wind and future challenges

This paper reviews the physics and correlations for the burning behaviour of pool fires in wind, discussing also challenges for future research on this topic. In the past decades, the burning behaviour of pool fires in still air, which is solely buoyancy driven, has been extensively studied. These studies are primarily focused on scale, radiation, soot, pressure and gravity effects. However, these phenomena and physics change significantly with much more complexity in the presence of wind, with regard to heat feedback and burning rate; flame morphological characteristics; flame turbulence, soot and radiation emission. Remarkable progress has been made in understanding the behaviour of the heat feedback and burning rate, flame tilt, flame length and flame base drag of wind-blown pool fires. Several semi-empirical correlations have been proposed for these quantities, based on experimental data and the physically dimensional analysis. However, for wind-blown pool fires, the flame soot and radiation emission coupling with complex flow turbulence scales due to the interaction of buoyancy with wind still require more basic research. All these processes are more challenging especially for wind-blown large scale pool fires, which require knowledge and understanding of the physics, especially for establishing evaluation methodologies of their hazard and adverse impact.     

Gas-Phase Mass Transfer Model for Predicting Volatile Organic Compound (VOC) Emission Rates from Indoor Pollutant Sources

Abstract Analysis of the impact of sources on indoor pollutant concentrations and occupant exposure to indoor pollutants requires knowledge of the emission rates from the sources. Emission rates are often determined by chamber testing and the data from the chamber test are fitted to an empirical model. While the empirical models are useful, they do not provide information necessary to scale the chamber data to buildings nor do they provide information necessary to understand the processes controlling emissions. A mass transfer model for gas-phase-limited mass transfer is developed and described in this paper. Examples of sources with gas-phase-limited emissions are moth cakes, floor wax, stain, and varnish. The mass transfer model expresses the emission rate in terms of a mass transfer coefficient and a driving force. The mass transfer coefficient can be predicted from correlations of the Nusselt number and the Reynolds number. The experiments and data analysis used to develop the correlation are described in the paper. Experiments to verify the assumptions used to describe the driving force are also described. Suggestions for using data from existing empirical emission models to determine parameters for the mass transfer model are provided. The mass transfer model provides a significantly better fit to data from an indoor air quality test house than does the empirical first order decay model.     

Characterization of fine particle emissions from incense burning

Incense burning is an important indoor source of airborne particles. In this study, the emission factors of PM_2.5 and its chemical constituents emitted from six different brands of incense sticks were determined. Controlled experiments were conducted to measure the mass concentration of PM_2.5 and to determine its chemical composition (elemental carbon (EC), organic carbon (OC), metals, and ions). Measurements showed that the emissions vary for different brands of incense sticks, with smokeless incense sticks emitting the least amount. PM_2.5 emission factors range from 0.4 (smokeless incense stick) to 44.5 mg/g. Results also show that the amount of metals emitted is highly dependent on the quantity of metals present in the incense sticks. In addition, the information obtained from the controlled experiments is used to predict the concentration of PM_2.5 at incense smoke-influenced microenvironments, such as temples and homes, in order to assess the potential indoor exposure during the course of incense burning. Comparison with indoor air quality guidelines suggests that inhalation of incense smoke can pose adverse health impacts.     

Emission factors of gaseous pollutants from recent kerosene space heaters and fuels available in France in 2010

Laboratory measurements of the gaseous emission factors (EF) from two recent kerosene space heaters (wick and injector) with five different fuels have been conducted in an 8-m(3) environmental chamber. The two heaters tested were found to emit mainly CO(2), CO, NO, NO(2), and some volatile organic compounds (VOCs). NO(2) is continuously emitted during use, with an EF of 100-450 μg per g of consumed fuel. CO is normally emitted mainly during the first minutes of use (up to 3 mg/g). Formaldehyde and benzene EFs were quantified at 15 and 16 μg/g, respectively, for the wick heater. Some other VOCs, such as 1,3-butadiene, were detected with lower EFs. We demonstrated the unsuitability of a 'biofuel' containing fatty acid methyl esters for use with the wick heater, and that the accumulation of soot on the same heater, whatever the fuel, leads to a dramatic increase in the CO EF, up to 16 mg/g, which could be responsible for chronic and acute CO intoxications. PRACTICAL IMPLICATIONS: Our results show that in spite of new technologies and emission standards for unvented kerosene space heaters, as well as for the fuels, the use of these heaters in indoor environments still leads to NO(x) levels in excess of current health recommendations. Whereas injection heaters generate more nitrogen oxides than wick heaters, prolonged use of the latter leads to a soot buildup, concomitant with high CO emissions, which could be responsible for acute and chronic intoxications. The use of a biofuel in a wick heater is also of concern. Maintenance of the heaters and adequate ventilation of the room during use of kerosene space heaters are therefore of prime importance to reduce personal exposure.     

Influence of modified pent roof combustion cavity on diesel engine performance and emission characteristics

The utmost vital role of the IC engine burning chamber is to offer correct mixing of air and fuel in a little time to lessen the ignition lag phase, which determines the quality of the combustion, performance and the exhaust emission characteristics. To attain this, a systematised air movement termed ‘air swirl’ is offered to create high comparative velocity amongst fuel droplets and air. In this work, the engine piston head is modified to a 6° angle at the crown part, and the engine performance and emission analysis are carried out. The modified piston promotes speedier mingling between the inducted air and injected fuel, which speeds up the combustion process. By modifying the combustion chamber, we obtained a very less amount of NO_x Emissions and a moderate amount of hydrocarbon and carbon monoxide emissions.     

Evaluation of emissions of total volatile organic compounds from carpets in an environmental chamber

An environmental test chamber with controlled temperature, relative humidity and airflow rate has been used to evaluate emissions of total volatile organic compounds (TVOCs) from 11 new carpets. The quantity of TVOCs emissions was measured by a gas chromatography/flame ionisation detector.The TVOCs emissions of each product were tested as a function of time. The results showed that the time dependence of TVOCs concentrations and the change of emission rates with time can be described by a double-exponential model. With this double-exponential model, the initial emission rates (E₁₀ and E₂₀) and emission decay constants (k₁ and k₂) in evaporation- and diffusion-dominated phases were simulated. These emission parameters could be used in estimation of TVOCs concentrations in an indoor environment. Model evaluation studies indicate that the Highclass carpet has the smallest model accuracy while the Double-diamond and Classic design carpets have the largest model accuracy.