2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
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Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology<br />
ple bags were used for all experiments. Both samples were<br />
analyzed by GC-MS and an overview of obtained odorant<br />
concentrations is given in Table II.<br />
Table I<br />
Odorisation Levels according to TPG 918 01(ref. 2 )<br />
Odorisation<br />
level Olfactory perception Comment<br />
(grade)<br />
0 Odour not detected –<br />
1 Very low intensity Odour threshold<br />
2 Weak odour –<br />
3 Mean odour Warning odour level<br />
4 Strong odour –<br />
5 Very strong odour –<br />
6 Extremely strong Upper limit of intensity<br />
odour<br />
Table II<br />
Samples overview<br />
DMS TBM Total<br />
[mg m –3 ]<br />
Sample 1 <strong>2.</strong>71 3.31 6.02<br />
Sample 2 3.32 4.35 7.67<br />
For the estimation of odorisation level shortened examination<br />
described in technical norm ČSn 38 5550 1 was<br />
applied. In this test the odour threshold (grade 1) is estimated<br />
as a first point and the warning odour level (grade 3)<br />
as a second point. From obtained data (mean value from all<br />
observers mean values) the dependence of odorisation level<br />
on odorant concentration in natural gas was created.<br />
The measurement was carried out by two different<br />
groups of observers.<br />
The first one (GROUP 1), consisted of professional<br />
observers who satisfied the conditions listed in ČSn En<br />
13725 3 for performing the olfactometry measurement.<br />
The second one (GROUP 2), consisted of observers who<br />
are performing the subjective odorisation control in gas distribution<br />
companies.<br />
Obtained data are given in Figs. 1. and <strong>2.</strong> Each of them<br />
represents the dependence of odorisation level on the odorant<br />
concentration in natural gas – air mixture.<br />
Conclusions<br />
Performed measurement shows considerable subjectivity<br />
of an olfactometry measurement of the odorisation<br />
level. While observers from Group 1 respond accurately with<br />
minimal deviations, observers from Group 2 respond in wide<br />
range of dilution with considerably scattered results. This<br />
result is connected with the sensitivity threshold across population<br />
and to some extent with professional deformation of<br />
s488<br />
Fig. 1. Dependence of odorisation level on the odorant concentration<br />
for Sample 1<br />
Fig. <strong>2.</strong> Dependence of odorisation level on the odorant concentration<br />
for Sample 2<br />
employees carrying out the on-site olfactometry odorisation<br />
control of nG at selected points on natural gas grid.<br />
From the data obtained from Group 1, the K value for<br />
the odorant used in samples can be estimated. This value<br />
is considerably lower than the K value, which is currently<br />
used in the Czech Republic (the obtained K value lies under<br />
0.003 mg m –3 comparing to published 0.07 mg m –3 in the<br />
national technical regulation 2 ).<br />
As a main result of accomplished experiments it can be<br />
strictly recommended to prefer objective method for periodic<br />
odorisation control. nowadays gas distribution companies<br />
slowly change the way of odorisation control considering the<br />
objective control as the guarantee of safe gas distribution and<br />
utilization up to end customers.<br />
This work has been partly supported by MSM 604 613<br />
73 04.<br />
REFEREnCES<br />
1. ČSn 38 5550; Odorizace topných plynů, 1986.<br />
<strong>2.</strong> TPG 918 01; Odorizace zemního plynu, 200<strong>2.</strong><br />
3. ČSn En 13 725; Kvalita ovzduší. Stanovení koncentrace<br />
pachových. látek dynamickou olfaktometrií, 2003.
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