2009 NASM Odour Guide for
Ontario Regulation 267/03 made under the Nutrient Management
Part 8 - Odour Assessment Test: Method
Table of Contents
- Laboratory Sampling Method
- In-Field Sampling Method
- Area Source - EPA style Flux Chamber Sampling Procedure
- Sample Evaluation/Odour Detection Threshold Determination
The intent of the odour assessment test is to, as accurately as
possible, determine the odour generated from the activity in the
field. All odour assessment tests must be conducted at the maximum
application rate approved for the site and the NASM used must be
representative of the material to be applied. For example, the depth
of NASM in the flux chamber must match the depth of NASM applied
to the land surface.
Laboratories participating in odour assessment testing are required
to have sound quality criteria for the overall performance in the
odour assessment test. The testing laboratory must comply with the
applicable quality criteria by means of performance testing as specified
in Clause 5 of EN 13725:2003
It is recognized that odour assessment tests conducted in a laboratory
may result in a higher odour detection threshold than an odour assessment
test conducted at an actual application site where there is a porous
substrate underneath (i.e. soil). An odour assessment test conducted
in a laboratory represents a conservative approach to classifying
The generator must submit the methodology proposed for the odour
assessment test to the Director prior to doing the test. For compliance
purposes, the method must be comparable to the standard methods
in section 8 of this guide. An odour assessment test carried out
without first discussing the methodology with the Director will
not be accepted by the Director as part of a NASM plan approval.
There are two acceptable methods for collecting odour samples for
evaluation by the odour evaluation panel: a Laboratory Sampling
Method and an In-Field Sampling Method.
8.1 Laboratory Sampling Method
When an odour assessment test is done for the purpose of classifying
a material, a minimum of three samples of the NASM must be collected
for analysis at a laboratory. The laboratory method used must be
comparable to the standard methods in section 8.3 of this guide
using an EPA style flux chamber with a diameter of 40.6 cm and area
coverage of 0.13 m2 with sweep gas flow rates metered
at 5L/min. NASM samples should be analyzed within 5 hours of collection
but must not be analyzed later than 24 hours after collection.
8.2 In-Field Sampling Method
If the in-field method is to be used, a minimum of 3 triplicate
samples collected from a minimum of three locations that are representative
of the spreading area shall be analyzed. The in-field method used
must be comparable to the standard methods in section 8.3 of this
guide using an EPA style flux chamber with a diameter of 40.6 cm
and area coverage of 0.13 m2 with sweep gas flow rates
metered at 5L/min. Field assessments for odour must be analyzed
within 3 hours of the application of the NASM to the site.
8.3 Area Source - EPA style Flux Chamber Sampling
This method can be used to obtain odour samples either in the field
from area sources with no induced flow, including but not limited
to land application sites or in the laboratory. The flux chamber
system described below can be set up in the field or in the laboratory.
Area sources are rarely homogeneous in nature. As a result, it
is important that a well developed sampling strategy is employed
to ensure that the samples collected provide a fair representation
of the odour emission potential of the source as a whole. This may
require sampling to be completed at multiple locations and/or times,
for each individual source.
A sketch of an acceptable area source odour sample collection system
is shown in Figures 8-1 and 8-3. Other odour sample collection systems
and procedures may be used, provided it can be demonstrated that
they are comparable to the standard methods in section 8.3 of this
guide and are acceptable to the Director.
Note that sampling, using this approach, is not to be conducted
on rainy days (or when rain occurs within 24 hours prior to the
scheduled sampling) as the rain will interfere with the normal generation
and release of the odorous emissions (odour scrubbing effect).
The following apparatus are used when collecting odour samples
using either of the methods presented in sections 8.1 and 8.2 of
Sample line - made of Teflon®, or glass; the
distance between the probe and the sample container shall be kept
to a minimum. All fittings shall be clean and odour free and a comparable
level of odour resistance of Telfon® or stainless steel composition.
Sample containers - material of construction shall
be Tedlar®, Teflon® or any other materials (such as Nalophan®)
which will not compromise the integrity of the sample. When such
other materials are proposed, approval from the Director is required.
The sample container shall be of sufficient volume to carry out
a minimum of a six member odour panel evaluation.
Sample lung - rigid vessel or container, capable
of maintaining a vacuum sufficient to pull the sample from the exhaust
stream, within the time required.
Pump - Leak free Teflon® coated diaphragm-type
pump (with adjustable flow) or equivalent, which is capable of delivering
at least 1 litre/minute.
Flow meter - Two (2) flow meters with a 0 to 5
litre flow range.
Neutral gas - nitrogen (4.8 grade or higher) or
air that is treated in such a way that it is as odourless as technically
Flux Chamber - Enclosure with a cylindrical shaped
base and a spherical top, constructed of stainless steel or plexiglass.
The unit shall be equipped with odour free fittings which will allow
for the introduction of neutral (sweep) gas, the extraction of a
gaseous sample and the relief of sweep gas pressure (i.e. with a
bleed valve). See Figure 8-1 for a diagram. The flux chamber shall
be equipped with a flotation device for sampling liquid surfaces.
The sample containers shall be preconditioned by heating to 70°C
(158°F), and flushed continuously with neutral gas for a minimum
of 24 hours. Note that materials other than Tedlar® and Telfon®
may not require such preconditioning. However, guidance in this
issue is required from the Director.
The flux chamber shall be clean and free of residual odour prior
to each use. The flux chamber must be tested using blanks between
each use to confirm that it is odour free.
The sample transfer line must be clean and free of residual odour.
If any contamination is observed on the sample transfer line, the
sample transfer line must be replaced. A new and/or clean odour
free sample line must be used for each source being measured.
8.3.3 Sampling Procedure
Assemble the odour sample collection system and place the flux
chamber over the surface area to be tested. Ensure that the cylindrical
walls of the flux chamber are slightly below the sampling surface
thereby preventing the introduction of ambient air into the chamber.
Start the flow of metered neutral sweep gas into the flux chamber.
The flow rate shall be metered at 0.00064 m3/s based on one square
metre of coverage. Using an EPA style flux chamber with a diameter
of 40.6 cm and area coverage of 0.13 m2, sweep gas flow
rates shall be metered at 5L/min.
Flux chambers covering a larger surface area will require a higher
sweep gas flow rate. In such cases, the sweep gas flow rate results
will need to be normalized to 0.00064 m3/s based on one square metre
Allow a minimum of four (4) air exchanges to occur within the chamber
prior to drawing a sample. Each air exchange represents passing
a volume of sweep gas into the flux chamber that is equal to the
To condition the sample container, connect it to the sample line
within the rigid vessel. Seal the vessel and start the pump. Fill
the sample container and stop the pump. Empty the sample container
and repeat the above procedure. The sample container is now conditioned
for the collection of odour samples.
Reconnect the conditioned sample container to the sample line within
the rigid vessel, seal the vessel and begin sampling by starting
the pump. The sample flow rate is required to be such that the sample
container is filled over a 10 minute sampling period. The sweep
gas volumetric flow rate must exceed that of the sample flow rate.
Record all data according to Figure 8-2.
A minimum of three separate samples shall be collected from each
source but, as indicated previously, area sources are rarely homogeneous
in nature. The number of separate samples may be higher than three
depending on the number of selected locations that will provide
a fair representation of the odour emission potential of the source
as a whole.
Note that when using the flux chamber approach for collecting odour
samples, the odour concentration is calculated based on the sweep
gas rate; meaning that the rate of odourant released from the source,
may not be equivalent to the rate of the flux chamber sweep gas.
The flux chamber sweep gas rate, and its normalization, is used
for convenience; as the rate of odourant release is very complicated
to calculate. The rate of odourant release from a surface area will
depend (among other parameters) on the temperature of the surface,
the porosity of the surface, ambient relative humidity, the substance
chemical and physical composition releasing the odourant, the surface
tension between the odourant and the surface area, and the sweeping
effect of the wind on the surface area.
8.3.4 Sample Recovery
After completion of the 10 minute sample collection, the sample
container is immediately sealed, labeled and shielded from direct
sunlight. To protect from photo-chemical degradation samples shall
be placed in a dark or opaque container for storage and transport.
Samples shall be transported to an accredited odour analysis laboratory
to be analyzed within 24 hours of sample collection.
Note: Do not use stickers, tapes or other adhesive/solvent
based products to label Tedlar® or Teflon® sample bags as
there is the potential for odours to migrate into the sample container.
8.4 Sample Evaluation/Odour Detection Threshold
8.4.1 Dilution Apparatus
The dilution apparatus is the equipment used to mix neutral gas
with the sample of odourous gas at set ratios prior to evaluation
by the odour evaluation panel. The EN 13725:2003 sets out the requirements
for the general properties of materials in Clause 6.1 and the dilution
apparatus in Clause 6.5.
8.4.2 Odour Evaluation Panel
The selection of the odour evaluation panel is critical for an
objective and unbiased evaluation of the subject NASM. The panel
must have a minimum of 6 members. Panel member selection criteria
must be based on the criteria established in EN 13725:2003 Clause
8.4.3 Odour Evaluation and Calculation of Odour Concentration
The EN13725:2003 recommends two Modes of Presentation (Binary and
Forced Choice) for the evaluation of odour by the panel. Either
method can be used in the evaluation of the odour from a NASM that
is to be applied to agricultural land under O. Reg 267/03. The criteria
for each mode of presentation are in Clause 8 of EN 13725:2003.
The odour detection threshold is calculated as the geometric mean
of the individual panelist responses. The odour concentration (ou/m3)
is equal to this numeric value.
Pre-dilution of samples may be required in situations where the
odour concentration is so high that it exceeds the dilution capability
of the olfactometer, or in the case that a wet source results in
the formation of condensation in the sample bag. In the case that
field dilution (pre-dilution) is employed, the DT is the product
of the pre-dilution ratio and the geometric mean of the individual
odour panelist responses.
Example calculations for determining odour concentration and odour
detection threshold are in Appendix F of EN 13725:2003.
Once the odour detection threshold of the subject NASM has been
determined it can be assigned an odour category based on the limits
established for OC1, OC2 and OC3.
Figure 8-1. Sketch of an Acceptable Sampling
Train for Odour Sampling (Flux Chamber Approach).
Figure 8-2. Flux Chamber Odour Sample Data
Figure 8-3. Flux Chamber Odour Sampling Configuration.