The odour laboratory is accredited for sampling, measuring and analysing odour emissions from industry, plants, restaurants and other odour emitting companies.
Odour panellists smelling odour samples in the olfactometer
The odour laboratory consists of the following:
Instrument park for sampling, measuring and analysing odour samples
Olfactometer to assess the odour strength of the odour samples
A panel of trained odour panellists
A workshop for the production of odour bags
The odour laboratory’s measurements and analyses are most often carried out as:
documentation of compliance with limits for airborne odour for authorities, e.g. in relation to the company's environmental approval or the Danish Environmental Protection Act
quality assurance of effects when setting up filters to reduce airborne odour, e.g. biofilter, carbon filter, odour washer, etc.
In addition, we carry out a number of customised odour analyses, e.g. the smell of different types of sludge from sewage systems or odour of e.g. packaging or other products with residual odour from manufacturing.
In contrast to most chemical pollution, odours can be registered immediately, and therefore also often lead to complaints when companies emit odours. Irrespective of whether the odour is pleasant or unpleasant, it can be experienced as nuisance by neighbours.
Odours are measured by collecting air from the source, e.g. a stack, in a bag. This air is analysed within 30 hours in an olfactometer.
The analysis is performed by an odour panel comprising a minimum of four persons in our own odour laboratory. The panellists sniff to samples which are diluted less and less, until the panellists can perceive weak odour. The degree of dilution is a measure of the odour content in the bag. The panellists’ description of the odour is noted – e.g. rotten, chemical or sweet.
How odour samples are collected and analysed is described in a European standard, EN 13.725.
The sample bag with the odour sample is mounted on the tube in the lower right corner, and by using clean air, the air in the bag is diluted before presenting it to the odour judges (panellists).
The olfactometer dilutes the samples using compressed air and runs an automatic series of varying dilutions. Four panellists are used in the analysis of the air and they are exposed to the series of varying dilutions and mark once they can smell the sample.
At first, it is diluted so much that no one can smell anything, and after that the smell is gradually made stronger. When a panellist can smell something at e.g. 2,000 times the dilution, a button is pushed (bottom centre of the image). Once each panellist has detected the odour twice, a mean value can be calculated for the sample.
Results are given in odour unit/cubic metre (o.u./m³).
We select odour panellists from ordinary people who are tested against the reference substance n-butanol.
The panellists’ odour threshold for this substance must be within the limits defined by the standard for odour analysis. If they are within the limits, such individuals are suitable as panellists and called for odour tests.
Odour is measured by collecting a bag of air from the chimney, which is analysed within thirty hours in a so-called olfactometer, which dilutes the odour samples in a controlled manner.
At the odour laboratory, we make bags for collecting odour samples. We use Nalophan, which is, among other things, used for packing food items and comes in endless “tubes”. To make a bag, we weld a piece of e.g. half a metre at both ends and put a teflon hose fitted with a teflon plug in the one corner.
We measure the hydrocarbon and carbon dioxide content with a gas monitor to obtain additional information on the contents of the samples.
Here, air is being blown over a sample of wastewater to assess how much odour is released when the wind blows over a wastewater basin. We analyse the air in the olfactometer and, by using calculations, we can estimate the odour from the wastewater basin.
Our olfactometer is a TO8 from the company Olfasense. The sample bag is mounted on, and with the help of clean air, we dilute the air in the bag before presenting it to the odour panellists. At first, we dilute it so much that none of the panellists can smell anything, and after that the smell is gradually made stronger. When a panellist can smell something at e.g. 2,000 times the dilution, they push a button. Once each panellist has detected the odour twice, we can calculate a mean value for the sample. Results are given in odour unit/cubic metre (o.u./m³).
Our methods for the collection and analysis of odour samples take place in accordance with DANAK accreditation 51. We are accredited according to ISO 17025, and the odour analyses comply with the descriptions in DS/EN 13725 and the Danish Environmental Protection Agency’s method sheet MEL-13.
