Combustible air fresheners are known to release numerous volatile organic compounds (VOCs) including both pleasant aromas and toxic components into the indoor environment. Scented candles have gained popularity over the past 30 years, in America retail sales of candles are estimated at approximately $2 billion annually.1 Whilst the abundance of these products increases, the focus on emission of chemicals has also grown. With the advent of mandatory testing for building materials used indoor in Europe, it was inevitable that Combustible Air Fresheners would come under scrutiny. CEN/PC 421 the European committee for Emission safety of combustible air fresheners has prepared three standards: “Development of standardised test methods for the emissions resulting from the use of combustible air fresheners and similar products”, “Methodology for the assessment of test results and of acceptable emission limits” and “Methods to define appropriate user safety labelling related to the emissions”.

Caroline Widdowson Markes International, Gwaun Elai Medi-Science Campus, Llantrisant, RCT, UK.

Introduction

Markes InternationalT: +44 (0)1443 230935 F: +44 (0)1443 231531 E: enquiries@markes.com W: www.markes.com

Sampling and analysis of combustible air fresheners

New Methods: Emission safety of combustible air fresheners

Conclusions

Safety requirements for candles are described in an EU Directive on general product safety, which states that for indoor candles, hazardous substances, including VOCs, created during the burning process shall be minimised as far as possible. In the absence of limit values set by individual EU member states, the concentration levels for VOCs released into the indoor environment should not exceed recommended limits laid down in the “WHO Guidelines for indoor air quality”. 2

References

1. Derudi, M. et al., Emissions of air pollutants from scented candles burning in a test chamber. Atmospheric Environment, 2012, vol 55, pp. 257-262.

2. Anon., 2001. 2001/95/EC of the European Parliament, Brussels: European Commission.3. CEN, 2015. EN 16738 – Emission safety of combustible air fresheners: Test Methods. Brussels: CEN-

CENELEC.4. CEN, 2015. EN 16740 – Emission safety of combustible air fresheners - User safety information.

Brussels: CEN-CENELEC.5. CEN, 2015. EN 16739 – Emission safety of combustible air fresheners: Methodology for the

assessment of test results and application of recommended emission limits. Brussels: CEN-CENELEC.

New European standards specifies a test method (EN 16738 – Emission safety of combustible air fresheners: Test Methods) for the determination of emissions resulting from the use of combustible air fresheners into indoor air by means of chamber sampling (according to EN ISO 16000-9) and analysis by thermal desorption–gas chromatography–mass spectrometry (GC–MS), a technique for the analysis and quantitation of organic volatile and semi-volatile compounds, and HPLC for Formaldehyde. This standard defines specific testing conditions for the measurement of the emissions from combustible air fresheners which minimises the effect of testing on the combustion process. This standard provides a measurement method for the determination of the following non-exhaustive list of target substances emitted directly from the burning process; VOC, benzene, naphthalene and formaldehyde.3

Methodology for the assessment of test results and application of recommended emission limits has been defined. The standards specify the methodology for the assessment of test results from the emissions of a combustible air freshener, when tested according to EN 16738 and followsREACH Guidance and consumer habits and practices to produce a consumer exposure assessment. The methods provide reference to published emission limit or guidance values.4Additionally, the methods define appropriate user safety labelling related to the emissions from combustible air fresheners.5 However, in addition to standardized testing of benzene and naphthalene, this process also enables the manufacturer to identify all the VOCs of interest from product to product, consequently giving useful data for the formulation and R&D process.

Combustible air fresheners, i.e.

Scented candle

Scented oil lamp

Incense

Catalytic burner

Catalytic lamp

Samples are placed inside a small chamber (1m3) held at 25°C, 50% RH and ignited following parameters listed in Table 1. Sorbent tubes are attached to the outlet of the chamber and the vapours are drawn onto the sample tube using a pump for analysis of VOC and SVOCs by thermal desorption GC–MS. To sample Formaldehyde the vapours are drawn onto DNPH cartridges for HPLC analysis.

Sample type Burning time (hr)

Air Change/hour

(h-1)

Equilibration time (min)

Number of samples in

the chamber

Number of samples

outside the chamber

Sampling time (min)

Scented candle ≥ 4 2 ± 0.2 120 ± 5 2 3 60 ± 5Scented candle ≥ 2 and ˂ 4 2 ± 0.2 90 ± 5 2 3 60 ± 5

Incense n/a 2 ± 0.2 5 ± 1 2 optional *Oil Lamp n/a 2 ± 0.2 120 ± 5 2 optional 60 ± 5

Catalytic Lamp n/a 2 ± 0.2 120 ± 5 2 optional 60 ± 5Scented candle with 2

or more wicks ˃ 4 2 ± 0.2 120 ± 5 1 1 60 ± 5

*adjust to combustion time, max 60 mins

Table 1: Chamber sampling parameters from EN 16738 - Emission safety of combustible air fresheners: Test Methods

Figure 1: Series of methods and image of a combustible air freshener, scented candle

Figure 2: Listed combustible air freshener, image of Incense

Weak Medium Strong

SVOC VOC VVOC

Sample in Desorb Flow

Figure 3: Illustration of a multi-bed sorbent tube

Figure 4: ACTI-VOC™ pump

EN 16738 – Emission safety of combustible air fresheners suggests the use of multi-bed sorbent tubes and focusing traps specifically with the following sorbent combinations:

Weak graphitized carbon black backed up a medium strength graphitized carbon black Weak graphitized carbon black backed up a medium strength graphitized carbon black further

backed up by a carbonized molecular sieve.

Analysis of the samples collected on the sorbent tubes is carried out using thermal desorption (Figure 5), in conjunction with gas chromatography–mass spectrometry (GC–MS). This approach allows comprehensive VOC and semi-VOC profiles to be generated, and target compounds reliably identified, even when they are present at trace levels.

Figure 6: Two different Incense sticks sampled and analysed under the same conditions using chambers,TD–GC–MS.

Active (pumped) sampling onto sorbent tubes is a versatile option for simultaneous monitoring of multiple compounds. The vapours from the chamber are pumped onto a sorbent tube (Figure 4)

A wide range of sorbents are available, and these can be classified generally as weak, medium or strong. Less volatile analytes are trapped on weaker sorbents and the more volatile on stronger sorbents (Figure 3). If a wide volatility range of compounds is to be monitored, it is often necessary to pack the tube with more than one sorbent material, arranged in order of increasing strength from the sampling end.

1. Propene2. Methanol3. Chloromethane4. Methyl chloride5. Acetone6. Propanol7. Furan8. Acetic acid methyl ester9. 2,3-Butanedione10. 2-Butanone11. Hexene12. 3-Methyl furan13. Hexane14. 2-Methyl furan15. Methyl proprionate16. Benzene17. 1-Hydroxy-2-propanone

18. 2-Pentanone 19. Pentadione20. 2,5,-Dimethyl furan21. 1-Methyl pyrrole 22. Toluene23. Hexanal24. Furfural25. Ethyl benzene26. Xylenes 27. Styrene28. Methoxy benzene29. Benzaldehyde30. Benzonitrile31. Phenol32. Benzofuran33. Decene34. Limonene

35. Phenyl ester acetic acid36. Butyl benzene37. 2-Methoxy phenol38. Benzoic acid methyl ester39. 2-Methyl benzofuran40. Tetramethyl benzene41. Phenylmethyl ester acetic acid42. 2-Methoxy-4-methyl phenol43. Naphthalene44. 2-Ethyl-2-methoxy phenol45. Tridecane46. Dimethoxy phenol47. Biphenyl48. Tetradecane49. Pentadecene50. Pentadecane51. Allethrin

Product A

Product B

While the current standard method specifies benzene (16) and naphthalene (43), a wide range of compounds of varying volatility can be detected and quantified (Figure 6). These included fragrance and flavour compounds that are of interest and in some cases insecticides with possible negative health implications, i.e. allethrin(51), a potent insecticide which causes respiratory issues and itching, burning and tingling feeling when in direct contact with skin.

Figure 5: Markes International TD100-xr™, automated thermal desorption instrument for analysis of VOCs &SVOCs.

The two products (A and B) contain a diverse range of ingredients from fragrant essential oils to binding agents, incense sticks have received increasing attention because of the potential for harmful components to be released when they are burnt. Manufacturers are also keen to understand the fate of the various components of the formulation.

EN 16738 – Emission safety of combustible air fresheners: Test Methods.

EN 16740 – Emission safety of combustible air fresheners –User safety information.

EN 16739 – Emission safety of combustible air fresheners: Methodology for the assessment of test results and application of recommended emission limits.