Methods of sensory evaluation of odour

Transcription

1 Methods of sensory evaluation of odour & 50 m 3 test facility at Arlon laboratory Anne-Claude ROMAIN, Jacques NICOLAS, Christophe DEGRAVE Department "Environmental Sciences and Management" Research group "Environmental Monitoring" ARLON

2 1. Methods of sensory evaluation of odour

3 Why sensory evaluation? Chemical VOC profiles are not sufficient to evaluate the odour acceptability of building material A B C A B C GCMS provides concentrations of individual chemicals, but not the global odour perception Dangerous to base the global evaluation on the sum of individual concentrations synergy/inhibition the most odorous compound may be among the ones which are the least concentrated

4 Sampling Odour sample are collected in litres bags. The bag material must be odour free without reaction or adsoption with the sample impervious, to prevent significant losses before measurement Pumping system cannot interact with the sample Tedlar bags (PVF) Sealed-barrel maintained under negative pressure Air drawn into the bag by the pressure difference

5 Different components of odour Intensity Concentration Hedonic tone Odour descriptor

6 Intensity Describes what is perceived by the human nose how "strong" the odour is, above the perception threshold Measured by sensory assessment with human panels on an odour intensity reference scale E.g. : classifying the odour magnitude in accordance with the concepts specified in a 7 level-scale (VDI ) sometimes difficult to class without reference Odour Extremely strong 6 Very strong 5 Strong 4 Distinct 3 Weak 2 Very weak 1 Not perceptible 0 Intensity level

7 Intensity Comparison with references : Standards AFNOR X ASTM E compare the intensity of the unknown odour with a reference odour emitted in varying concentrations usually : different dilutions of n-butanol Either in the lab, on the basis of samples, using an olfactometer button to select a level on a 1 to 10 scale actual odour sniffing port n-butanol comparison port or in the field, by comparing the actual odour to the one of different solutions of n-butanol

8 Concentration For a single compound, odour concentration chemical concentration Not linear with intensity described by power law or log law I klog C C 0 I I 0 C C 0 n

9 Concentration For a complex gas mixture compound, odour concentration = the number of times that the odour sample should be diluted in odourless air to reach the odour threshold of "average" people expressed in odorous unit per cubic meter (ou/m 3 ) Measured by an olfactometer (european standard EN 13725) E.g. : using a panel of 6 assessors

10 Hedonic tone Hedonic tone is the acceptability of the odour It describes the pleasant or unpleasant odour component E.g. : VDI level scale (may be selected on the olfactometer)

11 Odour descriptor Odour character is reported by using odour descriptors such as sweet smoky floral chemical spicy tobacco musty acid sour No accepted international standard vocabulary for building material chiefly valuable for the tracing of the source of odour (if there are some problems with the test arrangements)

12 Selection of test panelists One of the most important criterion is the representativeness to the target population. they must have a "normal" sensitivity not the "perfumer nose" not "anosmic people" EN13725 tested to n-butanol on the olfactometer a minimum of 10 times individual s average threshold measurement of n-butanol must be in the range of ppb antilog of the standard deviation must be less than 2.3

13 Relation between sensory measurement and chemical analyses GC-sniffing split at the GC-column outlet : either MS or sniffing port

14 2. Used methods for evaluation of building material emissions

15 Context Sensory evaluation not integrated in all labels and standards (AgBB) due to : Measurement uncertainties : e.g poorly reproducible results Ambiguous relation with VOC s determination in emission chambers E-nose technology for perceived air quality not successfull until today How integrate sensorial measurements in evaluation sheme (like AgBB) Various methods Usual odour dimensions : Intensity and acceptability (hedonic)

16 Sensory evaluation Quantitative Qualitative Detectability (concentration) Dilution factor (EN 13725) Intensity Magnitude estimation (ICL; VDI 3882(1)) Comparative methods (with references: acetone) (NFX , EN 13725) Quality Describe odour Hedonic tone Binary (yes/no) Continuous scale (M1; ICL; GUT; ) Category scale -4 to +4 (VDI )

17 Sensory tests and Labels 1. GuT, Oeko-Tex (for carpet), Natureplus labels Dimension : Intensity Trained panel, at least 7 persons In compliance with the Swiss standard SNV Small chamber : dessicator Method : 144 cm 2 sample thermostated for 15 hrs in a 2l desiccator T 37 C Hr 50 % Individual sniffing after this conditioning 30 minute intervals

18 Odour assessment of a sample that failed the test Intensity scale (magnitude) 1 = no odour 2 = not unpleasant 3 = slightly unpleasant 4 = unpleasant 5 = very unpleasant ( Intermediate values like 1,5; 2,5; etc. are possible ) To be ACCEPTED : grade 4 Time Test person Type of odour Assessment Grade 8:00 Person 1 sweetish slightly unpleasant 8:30 Person 2 chemistry, aromatic unpleasant 4 9:00 Person 3 chemistry unpleasant 4 9:30 Person 4 aromatic unpleasant 4 10:00 Person 5 pungent, chemistry unpleasant 4 10:30 Person 6 sweetish unpleasant 4 11:00 Person 7 sweetish, chemistry unpleasant 4 Evaluation as median: sweetish, chemistry,aromatic unpleasant 4 Evaluation as mean value: 4 Odour assessment of a sample that passed the test Time Test person Type of odour Assessment Grade 8:30 Person 1 fusty smell, new-product odour 9:00 Person 2 new-product odour slightly unpleasant slightly unpleasant 9:30 Person 3 fusty smell not unpleasant 2 10:00 Person 4 old slightly unpleasant 10:30 Person 5 new-product odour not unpleasant 2,5 11:00 Person 6 new-product odour not unpleasant 2,5 11:30 Person 7 fusty smell not unpleasant 2 Evaluation as median: new-product odour not unpleasant 2,5 Evaluation as mean value: 2, ,5 3

19 2. ICL: Indoor climate labelling (Denmark+Norway) sensory test at the «indoor-relevant time value» (based on chemical testing) : Dimensions : Acceptability and Intensity CLIMPAQ or similar small chamber Untrained panel 1. Acceptable (median of minimum 20 persons evaluations > 0) using the acceptability scale -1 : clearly unacceptable -0.1 : just unacceptable +1 : clearly acceptable +0.1 : just acceptable

20 Continuous acceptability scale (Fanger and Gunnersen) Imagine that you during your daily work would be exposed to the air form the test chamber: + 1 How acceptable is the air quality? Please mark on the scale and notice the distinction between acceptable and unacceptable

21 2. Intensity : 6-point continuous scale for odour intensity (magnitude and no comparison estimation). I > 2 (moderate odour)

22 3. M1 label, Building information foundation, RTS ( Finland) Dimensions : Acceptability and Descriptor CLIMPAQ or similar small chamber Untrained panel 2 levels

23 1. Untrained panel with at least 5 members : acceptability scale and descriptor 2. If panel acceptability vote between 0.4 and +0.4 at least ten more members : 15 evaluators, each giving 2 votes : 30 evaluations Classification : determination of the percent of unsatisfied Sensory evaluation Sensory assessment, percent of unsatisfied M1 <15% (result? +0,1) M2 <30% Odour description Not odorous Not significantly odorous M3 : > 30%

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25 4. Labels without odour test No sensory tests EMICODE Green label (USA) LQAI sheme (Portugal) Austrian ecolabel complementary AFSSET protocol (France) Mention of sensory tests but not yet included AgBB, Blue Angel For the time : no criterion for the sensory evaluation because no generally approved method New methods?

26 Selection of HEMICPD sensory test 1. Sampling Techniques Dessicator CLIMPAQ Evaluation in the chamber Flec Dynamic olfactometer (EN 13725)

27 Olfactometer Advantages Drawback Flow rate and dilution control Trained and calibrated panellists Laboratory measurements (standard conditions) Data acquisition Air samples in Tedlar Bags : Odour and VOC s simutlaneously sampled not applicable for low air volume Increase the reproducibility and the accuracy Comparison possible for the medium (VITO) and large chamber (Ulg) Not for the µchamber of BBRI More expensive than «dessicator» CLIMPAQ,

28 2. Odour dimensions Concentration? (Detection threshold ( EN 13725)) NO Not adapted for low odour emissions from building products Probably same concentration range for all the samples Not indicative of annoyance (or «perceived air quality) Odour concentrations measurements in the Ulg olfactometric laboratory «Resilient Novilon Flooring» material after 3 days Odour concentration (uo E /m³) TVOC (mg eqtoluène /m³) Medium chamber : bags sampled by VITO 93 (Bag A) confidence interval [59 to 147] Large chamber : bag collected by Ulg 81 confidence interval [51 to 181] 8 2 Low concentrations even for quite high VOC s emission Near the instrument limit of detection Large confidence interval

29 Intensity YES more indicative of annoyance (quality and quantity dimensions) more adapted for low odour emissions typical of building materials largely used in indoor Comparative method prefered : use of reference gas (acetone or butanol) Descriptors why not Better accuracy But very subjective, not accurate Hedonic tone YES annoyance dimensions (perceived air quality) largely used in indoor Acceptability continuous scale (Fanger) : untrained or Category scale (VDI ) : Reduce the subjective perception

30 3. Trained or Untrained Trained Usually with comparative scale Smaller number of panellist (max 10) to reach statistically reliable results Panels may become more comparable by training to meet common performance criteria Interlaboratory variations can be attributed to the panel differences. UnTrained No comparative scale Greater number of panellist (> 40) to reach statiscally reliable results Low repeatability Large standard deviation

31 HEMICPD and Sensory tests 1 quantification + 1 qualification method Intensity Hedonic scale Comparative method Category scale (-4 +4) Air sampled in Tedlar bags for VITO and Ulg chambers Sensory measurements in laboratory conditions (conform to EN 13725) With Trained panels (6 panellists simultaneously) Dynamic Olfactometer but Ulg is not equipped to perfom intensity and hedonic tests with its dynamic olfactometer (alternatives)

32 approach similar than : study by the Federal Institute for Materials Research and testing (BAM), the Hermann-Rietschel-Institute (HRI) of the Technical University of Berlin and the Federal Environment Agency (UBA) (June 2007) Study conclusions : Sampling the air in Tedlar bags Bags are transported to the laboratory Two stages measurements 1. Measurement of intensity (comparative scale with acetone and 8 trained panellists) 2. Hedonic Assessement (scale 4 to +4) Standard deviation for intensity evaluation (24%) lower than for hedonic assessment (66%) Better than expected thanks to Laboratory environement, trained panel, randon presentation Basis for the AgBB assessment

33 3. 50 m 3 test chamber

34 Laboratory built in the frame of the EC project " Improvement of transport safety by control of fog production in a chamber" ("FOG" project). Large test room : 4.8 x 4.0 x 2.6 m = 50.5 m 3 surrounded by a "buffer" zone

35 Two different systems of climate control : an air-based low-inertia system (ventilation) and a high inertia radiant system (floor and ceiling). control of temperature and air velocity

36 Close to a "real" room not perfectly clean, but versatile

37 Air flow Ventsorb 70 ENVIROCARB AP W 80 kg charcoal Corrugated 150 mm aluminium tube

38 HR % Set points and control (as close as possible to the "standard room" concept as defined by ISO ) Room temperature 23 C by floor heating Air exchange rate 0.5 vol/h Air flow rate 25 m 3 /h Air velocity m/s (not homogeneous) Floor surface = 20 m 2 loading factor = 0.42 m 2 /m 3 area specific air flow rate = 1.25 m 3 /m 2 h Hr in the fog chamber 2 temperature probes in ducts and 5 inside the test room 1 relative humidity probe inside the room Humidity not controlled, but rather stable around 50% /07/2007 3/07/2007 5/07/2007 7/07/2007 9/07/ /07/ /07/2007 Day 15/07/ /07/ /07/ /07/ /07/2007

39 Air sampling and analysis 1. Pumping the air in a 60 litres Tedlar bar (closed door) 2. Sampling the collected air in Tenax cartridge 3. Analyzing the sample air by TD-GCMS