Research & Science

Denmark belongs to the countries in Europe where most candles are used, especially during the long winters. A study which was conducted by a team of independent scientists examined data of 6.757 participants of the Copenhagen Aging and Midlife Biobank cohort. The researchers found no statistically significant association between candle use and the risk of cardiovascular and respiratory events. Interestingly, it was observed that frequent candle users were more physically active and had a higher socioeconomic status than non-users and those who used candles rarely.

The full PDF version of the study is available at no charge:

[1] Use of candles and risk of cardiovascular and respiratory events in a Danish cohort study – Loft – 2022 – Indoor Air – Wiley Online Library

The most comprehensive study that has ever been made in this area demonstrates new insights into the emissions of burning candles depending on their composition.

All investigations were carried out under controlled climatic conditions in an 8 m³ stainless steel chamber. Combinations of four different fuels (waxes) and five different fragrances in addition to one set of unscented control candles were examined. This resulted in 24 experiments, 20 with scented candles and four with unscented candles. The typical combustion gases carbon monoxide, carbon dioxide and NO_x, organic compounds, such as formaldehyde, benzene, and polycyclic aromatic hydrocarbons, PM_2.5 and ultrafine particles were monitored in the chamber air and the emission rates were determined. The data were statistically evaluated using parametric and non-parametric methods as well as hierarchical cluster analysis. Exposure scenarios typical for indoor environments were calculated from the emission rates and the results were compared with indoor guidance and reference values.

As expected, a multitude of gaseous and particulate emissions were detected. These were typical combustion products as well as evaporated constituents of the fragrance mixtures. In most cases, the calculated indoor concentrations were well below the respective guidance and reference values. The exceptions observed in some cases for nitrogen dioxide, acrolein and benzo[a]pyrene are discussed critically.

The full PDF version of the study is available at no charge:

[1] https://www.sciencedirect.com/science/article/pii/S0160412021002154

In December 2018, the Danish Environmental Protection Agency Miljøstyrelsen published a comprehensive research report [1] on their website that provides a number of important new findings on particles emitted by candles and their evaluation. The most important findings are probably that these particles almost entirely consist of water-soluble salts for most candles and that their soot content is very low. This differentiates them significantly from particles emitted by other sources, and they must be evaluated differently as a consequence. It is recommended to purchase high-quality candles and protect them from draught during burning.

Background

Small particles with a size of less than 2,5 µm can get into the alveoli of the lungs if they are inhaled. If these particles are persistent, i.e. not water-soluble, they can only be eliminated by the body very slowly and may cause health problems. Exhaust from diesel cars, tire abrasion or wood burning stoves are well-known sources of such particles into outdoor air. But there are also particles in indoor air, emitted by cooking, vacuuming or burning candles for example. In contrast to outdoor particles, there is not much knowledge of what health relevance these indoor particles have so far, however.

There have been numerous media reports in the past years, especially in Denmark, that identified candles as one of the main sources of fine particles indoors. The measured concentrations were often compared with those measured close to a main road and candles were branded as a considerable health risk. Consumers are deeply concerned accordingly, especially in Denmark where the candle consumption per capita is highest in Europe, but also in other countries. Miljøstyrelsen therefore commissioned several research projects with the objective to investigate the emissions from candles and help with the assessment.

Candle manufacturers organised in ECA attach utmost importance to high-quality candles that are safe to use by consumers. There is a long tradition of independent scientific research in order to constantly improve both quality and safety aspects. Therefore, ECA and some of its member companies agreed immediately when Miljøstyrelsen invited them to work in a new research project under scientific guidance of the Danish Technological Institute. One of the main objectives of the project was to scientifically determine the number and composition of particles and other substances emitted by candles during normal use. Based on that, the second main objective was to develop candles that emit a minimum of health relevant substances.

Findings

The project, which ran from January 2017 until June 2018, investigated a number of the most common candles in Denmark intensively and with state-of-the-art scientific methods. The most important findings are:

• Candles do indeed emit a comparably high number of fine particles during burning. But as long as the candles are protected from draught as instructed by the manufacturers, virtually all particles emitted by most candles consist of the salts used to treat the candle wicks. These salts dissolve easily in water, i.e. they are not persistent and can be excreted easily by the body.
• The soot content of the particles is very low and much lower than in diesel exhaust for example.
• Heavy metals, such as lead or nickel for example, could not be detected in the emissions.
• The emission of volatile organic compounds (VOC) was unremarkable and at very low levels.
• Due to these significant differences, particles emitted by candles cannot be compared directly with those emitted by other sources, e.g. by traffic.
• It is recommended to purchase high-quality candles, protect them from draught during burning and trim the wick if it gets too long.

Outlook

Due to the limited resources of the project, it was not possible to modify the candles in a way that all emissions would decrease to even lower levels simultaneously. But this is one of the open points which were picked up by yet another research project that was approved by the Danish Innovation Fund in October 2017 and will continue until summer 2021. It is expected that the project will provide additional key knowledge of the emission of particles and other substances and facilitate an objective evaluation of the health effects.

[1] https://www2.mst.dk/Udgiv/publications/2018/11/978-87-7038-009-6.pdf

Airborne compounds in the indoor environment arise from a wide variety of sources such as environmental tobacco smoke, heating and cooking, construction materials as well as outdoor sources. To understand the contribution of scented candles to the indoor load of airborne substances and particulate matter, candle emission testing was undertaken in environmentally controlled small and large emission chambers.

Candle emission rates, calculated on the basis of measured chamber concentrations of volatile and semivolatile organic compounds (VOC, SVOC) and particulate matter (PM), were used to predict their respective indoor air concentrations in a standard EU-based dwelling using two different models. The output has been used to estimate more realistic consumer exposure concentrations of specific chemicals and PM in candle emissions. Potential consumer health risks associated with the candle emissions were characterized by comparing the exposure concentrations with existing indoor or ambient air quality guidelines or, where not existent, to established toxicity thresholds. On the basis of this investigation it was concluded that under normal conditions of use scented candles do not pose known health risks to the consumer.

[1] https://www.sciencedirect.com/science/article/abs/pii/S0273230014000348

Burning of scented candles in indoor environment can release a large number of toxic chemicals. However, in spite of the large market penetration of scented candles, very few works investigated their organic pollutants emissions. This paper investigates volatile organic compounds emissions, with particular reference to the priority indoor pollutants identified by the European Commission, from the burning of scented candles in a laboratory-scale test chamber. It has been found that BTEX and PAHs emission factors show large differences among different candles, possibly due to the raw paraffinic material used, while aldehydes emission factors seem more related to the presence of additives. This clearly evidences the need for simple and cheap methodologies to measure the emission factors of commercial candles in order to foresee the expected pollutant concentration in a given indoor environment and compare it with health safety standards.

[1] https://www.sciencedirect.com/science/article/abs/pii/S1352231012002683

This study investigates PAHs indoor emissions from burning decorative candle in an indoor environment because emissions from burning wax in home have rarely been addressed. A total of 12 air samples were collected during the entire burning period of the decorative candles. Particulate and gaseous PAHs emissions were simultaneously measured.

The measured total PAHs concentration (particulate + aqueous phase + gas phases) for the candles, reported as mass of PAHs emitted/mass of candle burning, was between 2.3 and 49.8 μg kg−1 and mean 15 μg kg−1. Considering the volume of sampled air, the concentrations of total PAHs ranged from 7 ng m−3 to 267 ng m−3. Concentrations of B[a]P emitted by candles ranged from 0.1 to 7.5 ng m−3, while total carcinogenic PAHs, expressed as B[a]eq, ranged from 0.2 to 10.7 ng m−3. The values of all the isomeric indices calculated in this research are in good agreement to literature data for emissions from high temperature processes.

[1] https://www.sciencedirect.com/science/article/abs/pii/S1352231010010502

The aim was to determine the light intensity emitted by candles made of paraffin, beeswax, fat and stearic acid. In order to be able to reach a conclusion regarding how effectively combustion occurs with these different candle materials, an apparatus was developed which allowed wax consumption rates and light intensity to be determined simultaneously. The relationship between these two factors (light intensity/wax consumption) can be used to provide a unit of measurement for the effectiveness of the transformation of chemical energy into light.

Download the study summary as a pdf here.

The internationally funded study on candle emissions has confirmed that well-made candles of all major wax types (paraffin, soy wax, stearin, palm wax and beeswax) exhibit the same clean burning behavior and pose no discernible risks to human health or indoor air quality.

Download the study summary as a pdf here.

Common household open flame and radiant ignition sources are the actual or suspected cause for many fires. The purpose of this research is to identify the burning behavior and properties of common candles in order to provide additional tools for use by fire investigators. The properties of paraffin wax are obtained from the literature and from experiments. The candles are burned under controlled laboratory conditions to measure the mass burning rate, candle regression rate, flame height, and heat flux. Using the properties of paraffin wax and characteristics of the candles, numerous simulations are performed with the NIST Fire Dynamics Simulator (FDS) to model the burning rate and heat flux profile of the candle flame. The modeling results are then compared with the flame height and heat flux data obtained experimentally. The model facilitates an enhanced understanding of the structure of candle flames.

[1] https://www.nist.gov/publications/characterization-candle-flames

This article gives an overview and description of the raw materials and additives that are used for the manufacture of candles and explains the combustion process in the candle flame. Starting with the definition and classification of candles the criteria are presented which are crucial for the safe handling of candles i.e. ensuring they are harmless in relation to both people and the environment. The structure and content of a proposed European quality standard for candles are derived from these criteria.

Download the article as a pdf here.

(English translation, courtesy National Candle Association)

The study determined the emission of various pollutants from heavily fragranced paraffin wax candles in a standardized test apparatus under realistic conditions. It showed that the emissions pose no significant risk potential to the consumers of the candles.

Download the study report as a pdf here.

(English translation (combined Parts 1 & 2), courtesy National Candle Association)

The study determined the emission of various pollutants from lightly fragranced paraffin wax candles in a standardized test apparatus under realistic conditions. It showed that the emissions pose no significant risk potential to the consumers of the candles.

Download the study report as a pdf here.

(English translation, courtesy National Candle Association)

Both the waxes and wicks as well as the combustion gases of paraffin, stearin and beeswax candles without colour and lacquer were examined for their toxicological risk. Even. with an assumed “worst-case scenario” and allowing for governmental limits and specifications, the toxicological evaluation arrived at the result that the examined candles do not cause any additional health risk.

Download the study report as a pdf here.