The term odour refers to perception regarding smell or scientifically it can be called as “a sensation resulting from the reception of stimulus by the olfactory sensory system”. It can be unpleasant or pleasant but it is caused by inhaling air borne inorganics or organics. The ever growing population, urbanization and industrialisation has led to odour problem which has increased in to a large proportion and thus a need to control the problem has risen. The major reason of odour problem is no proper sanitation facilities for urbanization. Industrialisation is taking place at a very fast pace and it has added to the problem. Undesirable odour detoriates the air quality and affects the human lifestyle. Odour problem is one the most complex form of pollution.

1. ASSIGNMENT
ON
PROBLEM OF ODOR POLLUTIO N
AND ITS MANAGEM ENT SOLUTIO N
Submitted to:
Dr. N.A. Siddiqui
Professor & Head -Health, Safety, Fire & Environment Engineering Department
SUBMITTED BY-:
CHINTAN GUPTA - 500042035
RENJITH PAROLIA - 500043311
RICHA ARORA – 500043338
ROHIT BISHT – 500043049

2. TABLE OF CONTENTS
1. ODOUR POLLUTION AND ITS CONTROL 3
2. EFFECTS OF ODOUR 3
3. ODOUROUS COMPOUNDS 4
4. SOURCES OF ODOROUS COMPOUNDS 4
5. MEASUREMENT AND CONTROL TECHNIQUES OF ODOUR 5
5.1. MEASURING CONCENTRATION 5
5.2. INTENSITY 6
5.3. HEDONIC TONE ASSESSMENT 7
5.4. CHARACTER 7
5.5. INTERPRETING DISPERSION MODELING 7
5.6. SAMPLING FROM AREA SOURCES 7
5.7. DIRECT SAMPLING 7
5.8. INDIRECT SAMPLING 8
6. ODOUR CONTROL TECHNOLOGIES 8
6.1. ODOUR CONTROL FROM AREA SOURCES 8
6.2. ODOUR CONTROL FROM POINT SOURCES 9
7. INTERNATIONAL STANDARDS, LEGISLATIONS AND REGULATIONS W.R.T.
ODOUR 10
8. RECOMMENDATION 11
9. BIBLIOGRAPHY 11

3. 1. ODOUR POLLUTION AND ITS CONTROL
The term odour refers to perception regarding smell or scientifically it can be called as “a
sensation resulting from the reception of stimulus by the olfactory sensory system”. It can be
unpleasant or pleasant but it is caused by inhaling air borne inorganics or organics.
The ever growing population, urbanization and industrialisation has led to odour problem
which has increased in to a large proportion and thus a need to control the problem has risen.
The major reason of odour problem is no proper sanitation facilities for urbanization.
Industrialisation is taking place at a very fast pace and it has added to the problem.
Undesirable odour detoriates the air quality and affects the human lifestyle. Odour problem is
one the most complex form of pollution.
Odour Pollution has entirely different characteristics but can be compared to noise pollution.
Nuisance is the primary effect of odour on people similarly like noise pollution. The features
are:
1) Odour moves downwind
2) People can smell at a distance.
3) In presence of strong odour, weak odour cannot be perceived.
4) Two or more odours neutrals the smell of each other.
5) Odour is liked and disliked is based on the scent with pleasant or unpleasant
experience
6) Substances made of similar or dissimilar chemical contribution may have same odour.
7) Strength and nature of odour may change on dilution.
8) Most animals have keener sense of olfaction as compared to humans.
9) When same strength of odour is combined it may produce a combination that on eor
both may not be unrecognizable.
10) An individual quickly loose it awareness of sensation when constant intensity of
odour is perceived.
2. EFFECTS OF ODOUR
Odour affects living beings and humans in numerous ways. When the Smell is strong,
unpleasant or offensive it ruins a person’s enjoyment of life more when the smell is frequent
or persistent. There are many factors related to perceive nuisance are:
1) Odour occurrence frequency
2) Duration of exposure to odour
3) Offensiveness
4) Expectation and tolerance of the receptor
Toxic stimulants of odour can cause respiratory symptoms or ill health but foul smell may not
cause not direct damage to the body. The secondary effects of odour are insomnia, nausea
and discomfort. The odour with strong smell can cause nasal irritation, breathing problem or
asthma. Offensive odour has made environment odorous and loss of property value near
odour causing industries and plants.

4. 3. ODOUROUS COMPOUNDS
Odorous compounds include organic or inorganic molecules. The two major inorganic odours
are hydrogen sulphide and ammonia. Organic odours are usually the result of biological
activity that decomposes organic matter and forms a variety of extremely malodorous gases
including indoles, skatoles, mercaptans, and amines.
 Hydrogen sulphide: Hydrogen sulphide is the chemical compound with
the formula H2S It is a colourless gas with the characteristic foul odour of rotten eggs.
 Ammonia: Ammonia or azane is a compound of nitrogen and hydrogen with
the formula NH3. The simplest pnictogen hydride, ammonia is a colourless gas with a
characteristic pungent smell.
 Indole: Indole is an aromatic heterocyclic organic compound with formula C8H7N. It
occurs naturally in human feces and has an intense fecal odour. At very low
concentrations, however, it has a flowery smell.
 Skatoles: Skatole or 3-methylindole is a mildly toxic white, crystalline organic
compound belonging to the indole family. It occurs naturally in feces (it is produced
from tryptophan in the mammalian digestive tract) and coal tar and has a strong
fecal odour.
 Mercaptons: mercapton is an organosulfur compound with the chemical
formula CH3SH. It is a colourless gas with a distinctive putrid smell.
4. SOURCES OF ODOROUS COMPOUNDS
The major sources for odorous compounds include agricultural waste, food processing
industries, composting of municipal solid wastes, livestock production industries,
semiconductor industries, and the incomplete combustion of hydrocarbon fuels in a range of
industries. The use of ethanol in industries also results in the release of odorous carbonyl
compounds into the atmosphere.
Odour sources can be classified as follows.
Sources of Odours are:
 Point Sources: Point sources are confined emissions from vents, stacks and exhausts.
 Area Sources: Area sources may be unconfined like sewage treatment plant, waste
water treatment plant, solid waste landfill, composting, household manure spreading,
settling lagoons etc.
 Building Sources: Building sources of odour like pig sheds and hog confinement
chicken.
 Fugitive Sources: In this source of odour, emissions are of fugitive nature like odour
emissions from soil bed or bio-filter surface.

5. 5. MEASUREMENT AND CONTROL TECHNIQUES OF ODOUR
Odor measurement is essential for odor regulation and control.[19] An odor emission often
consists of a complex mixture of many odorous compounds. Analytical monitoring of
individual chemical compounds present in such odor is usually not practical. As a result, odor
sensory methods, instead of instrumental methods, are normally used to measure such odor.
Odor sensory methods are available to monitor odor both from source emissions and in the
ambient air. These two diverse circumstances require different approaches for measuring odor.
The collection of odor samples is more easily accomplished for a source emission than for an
odor in the ambient air.
Field measurement with portable olfactometer seems more effective, but the use of field
olfactometer is not regulated in Europe so far, while it is popular in the U.S. and Canada, where
several States set limits at the receptor sites or along the perimeter of odor emitting plants,
expressed in units of dilution to threshold (D/T)
Different aspects of odor can be measured through a number of quantitative methods, such as
assessing concentration or apparent intensity. Initial entry into a room provides the most
accurate sensing of smell, before habituation begins to change perception of odor.
Sensation of odor has 4 properties related to threshold and tolerance: odor concentration, odor
intensity, odor quality, and hedonic tone.
5.1. MEASURING CONCENTRATION
Odor concentration is an odor's pervasiveness. To measure odor sensation, an odor is diluted
to certain amounts to reach a detection or recognition threshold. The detection threshold is the
concentration of an odor in air when 50% of a population can distinguish between the odorous
sample and an odor free blank. The recognition threshold is the concentration of an odor in air
in which 50% of a population can discern from an odorous sample and odor free blank.The
recognition odor threshold is usually a factor of 2 to 5 times higher than the detection threshold
The measurement of odor concentration is the most widespread method to quantify odors. It is
standardized in CEN EN 13725:2003. The method is based on dilution of an odor sample to
the odor threshold (the point at which the odor is only just detectable to 50% of the test panel).
The numerical value of the odor concentration is equal to the dilution factor that is necessary
to reach the odor threshold. Its unit is the European Odour Unit, OUE. Therefore, the odor
concentration at the odor threshold is 1 OUE by definition.
To establish the odor concentration, an olfactometer is used which employs a group of
panelists. A diluted odorous mixture and an odor-free gas (as a reference) are presented from
sniffing ports to a group of panelists. In comparing the odor emitted from each port, the
panelists are asked to report if they can detect a difference between the ports. The gas-diluting
ratio is then decreased by a factor of 1.4 or two (i.e., the concentration is increased accordingly).
The panelists are asked to repeat their judgment. This continues until the panelists respond
certain and correct twice in a row. These responses are used to calculate the concentration of
the odor in terms of European odor units (OUE/m3).

6. The test persons must fulfill certain requirements, for example regarding their sensitivity of
odor perception. The main panel calibration gas to verify this requirement used is n-Butanol (as
1 OUE/m3≡40 ppb/v n-butanol).
To collect an odor sample, the samples must be collected using specialized sample bags, which
are made from an odor free material e.g. Teflon. The most accepted technique for collecting
odor samples is the lung technique, where the sample bag is placed in a sealed drum, and a
vacuum is placed on the drum, which fills the sample bag as the bag expands, and draws the
sample from the source into the bag. Critically, all components which touch the odor sample,
must be odor free, which includes sample lines and fittings.
A human's odor detection threshold is variable. Repeated exposure to an odorant leads to
enhanced olfactory sensitivity and decreased detection thresholds for a number of different
odorants. It was found in a study that humans that were completely unable to detect the odor of
androstenone developed the ability to detect it after repeated exposure.
Humans can discriminate between two odorants that differ in concentration by as little as 7%.
There are a number of issues which have to be overcome with sampling, these include: – If the
source is under vacuum – if the source is at a high temperature – If the source has high humidity
Issues such as temperature and humidity are best overcome using either pre-dilution or dynamic
dilution techniques.
5.2. INTENSITY
Odor intensity is the perceived strength of odor sensation. This intensity property is used to
locate the source of odors and perhaps most directly related to odor nuisance.
Perceived strength of the odor sensation is measured in conjunction with odor concentration.
This can be modeled by the Weber-Fechner law: I = a × log(c) + b
I is the perceived psychological intensity at the dilution step on the butanol scale, a is the
Weber-Fechner coefficient, C is the chemical concentrations, and b is the intercept constant
(0.5 by definition)
Odor intensity can be expressed using an odor intensity scale, which is a verbal description of
an odor sensation to which a numerical value is assigned
Odor intensity can be divided into the following categories according to intensity:
0 – no odor
1 – very weak (odor threshold)
2 – weak
3 – distinct
4 – strong
5 – very strong
6 – intolerable

7. This method is applied by in the laboratory and is done so by a series of suitably trained
panelists/observers who have been trained to appropriately define intensity.
5.3. HEDONIC TONE ASSESSMENT
Hedonic assessment is the process of scaling odors on a scale ranging from
extremely unpleasant via neutral up to extremely pleasant. It is important to note that intensity
and hedonic tone, whilst similar, refer to different things. That is, the strength of the odor
(intensity) and the pleasantness of an odor (hedonic tone). Moreover, it is important to note
that perception of an odor may change from pleasant to unpleasant with increasing
concentration, intensity, time, frequency, and previous experience with a specific odor; all
factors determining a response
The overall sets of qualities are sometimes identified as the "FIDOL factors", (short
for Frequency, Intensity, Duration, Offensiveness and Location).
5.4. CHARACTER
The character of an odor is a critical element in assessing an odor. This property is the ability
to distinguish different odors and is only descriptive. First a basic description is used such as
sweet, pungent, acrid, fragrant, warm, dry, or sour. The odor is then referenced to a source such
as sewage or apple which can then be followed by a reference to a specific chemical such as
acids or gasoline
Most commonly, a set of standard descriptors is used, which may range from fragrant to sewer
odor. Although the method is fairly simplistic, it is important for the FIDOL factors to be
understood by the person recording the character. This method is most commonly used to
define the character of an odor which can then be compared to other odors. It is common for
olfactometry laboratories to report character as an additional factor post sample analysis.
5.5. INTERPRETING DISPERSION MODELING
In many countries odor modeling is used to determine the extent of an impact from an odor
source. These are a function of modeled concentration, averaging time (over what time period
the model steps are run over (typically hourly) and a percentile. Percentiles refer to a statistical
representation of how many hours per year, the concentration C may be exceeded based on the
averaging period.
5.6. SAMPLING FROM AREA SOURCES
There are two main odor sampling techniques, the direct odor sampling and the indirect odor
sampling technique. Indirect refers to collecting samples from the air stream which has already
passed over the emitting surface.
5.7. DIRECT SAMPLING

8. Direct refers to the placement of an enclosure on or over an emitting surface from which
samples are collected, and an odor emission rate is determined.
The most commonly used direct methods include the flux chamber and wind tunnels which
include the UNSW wind tunnel. There are many other available techniques, and consideration
should be given to a number of factors before selecting a suitable method.
A source which has implications for this method are sources such as bark bed biofilters, which
have a vertical velocity component. For such sources, consideration needs to be given as to the
most appropriate method. A commonly used technique is to measure the odor concentration at
the emitting surface, and combine this with the volumetric flow rate of air entering the biofilter
to produce an emission rate.
5.8. INDIRECT SAMPLING
Indirect sampling is often referred to as back calculation. It involves the use of a mathematical
formula to predict an emission rate.
Many methods are used, but all make use of the same inputs which include surface roughness,
upwind and downwind concentrations, stability class (or other similar factor), wind speed, and
wind direction.
6. ODOUR CONTROL TECHNOLOGIES
Odour control depends on type of sources and is discussed below:
6.1. ODOUR CONTROL FROM AREA SOURCES
For large area sources following methods can be used to reduce odour complaints.
i) Excluding development close to the site
Development close to the site is to be excluded. A reasonable “buffer zone” around the area
sources has to be determined. The actual size of the zone depends upon a number of factors,
including the size of the area from which odour emanates, the intensity of the odour being
emitted, the duration and frequency of the odour emissions, the actual process being
undertaken, the topography of the site, the weather conditions that prevails at the site. Green
belt development in the buffer zone may help at least partially to mitigate / obfuscate the odour.
ii) Ensuring that the operation is carried out under the best management practices
Best management practices (BMP) vary depending upon the industry producing the odour. For
all new developments, BMPs starts with the site selection and the building of the facilities.

9. iii) Nozzles, sprayers and atomizers that spray ultra-fine particles of water or chemicals
can be used along the boundary lines of area sources to suppress odours.
Rotary atomizer is one such technique widely recommended for effective control of odour in
case of area sources. The Atomizer uses centrifugal action by a spinning inner mesh to force
droplets on to an outer mesh which "cuts" the water into atoms. The rotary atomizer produces
millions of microscopic droplets of water -- up to 238 billion from single little droplets that are
thinner than a human hair and a fine spray which covers up to 30 metres. This creates a fine
mist, which is more effective with minimal use of water and electricity. There are a large
number of chemicals and proprietary products that claim to reduce odour when they are applied
to area sources. Atmospheric odour that is contained in a restricted area can be oxidized by
atomization of the chlorine dioxide. Odour from sources such as holding ponds, lagoons, and
sewage pre or post treatment effluent can be controlled by atomized spray of chlorine dioxide.
To reduce odour, chemicals have to be applied over very large area, the cost of materials and
labour would be very high. The large quantity of these compounds required could cause
pollution. The spray / atomizer techniques are used to conceal / mask odour also from building
and fugitive sources.
6.2. ODOUR CONTROL FROM POINT SOURCES
In case of point sources such as that of industries, the odour-causing gas stream can be
collected through piping and ventilation system and made available for treatment. Dispersion
method is the simplest of the methods that can be adopted for odour abatement. This is nothing
but to release odorous gases from tall stack. It results in normal dispersion in the atmosphere
and consequent decrease in ground-level concentration below the threshold value. Dispersal by
stacks requires careful consideration of the location & meteorological parameters, etc. In
general, dispersion of odour emissions via chimneys is not a recommended method. An array
of treatment technologies is available for control of odour from gas streams collected through
process ventilation systems. These include :
i) Mist filtration
ii) Thermal oxidation/ Incineration
iii) Catalytic oxidation
iv) Biofiltration
v) Adsorption
vi) Wet scrubbing/Absorption
vii) Chemical treatment
viii) Irradiation
ix) Masking
x) Condensation
xi) Green belt development
The choice of the technology is often influenced by the following factors:
• The volume of gas (or vapor) being produced and its flow rate
• The chemical composition of the mixture causing the odour

10. • The temperature
• The water content of the stream
7. INTERNATIONAL STANDARDS, LEGISLATIONS AND
REGULATIONS W.R.T. ODOUR
Many Countries have adopted measurements for controlling odour pollution, some of which
is given below:
Canada
Here the responsibility lies with the provinces. Different provinces have their own odour
policy.
Since 1976 Ontario has a regulations called Agriculture Code of Practice that quotes the
distance to be kept with the livestock facilities.
In Alberta, there are guidelines for air quality as H2S of 10 ppb/v on an hour average is taken
for the purpose of Odour Impact mangemnet. This leads to 20/ou m3 on the basis of the smell
of H2S only, with the threshold limit of 0.5ppb/v.
Denmark
Here the ground level concentration is to not exceed 5 – 10 ou m3, it depends upon the
location whether its redential or non- residential at 99%, with the average time of 1 min
New Zealand.
Here the Ministry of Environement, suggest that the air quality should be of 5 – 10 ou m3 at
99.5% to 99.9 %
Japan
Japanese Offensive Odour control law represents the odour intensity in terms of Odour Index,
that is:
Odour Index = 10 Log (Odour Unit)
Intensity value from 2.5 – 3.5 is acceptable. The intensity scale used is given below:
 0 – Not Percentile
 1 – Detectable Smell (faint)
 2 – Recognition ( Weakly quality perceptible)
 3 – Easily Quality perceptible
 4 – strong
 5 – Very strong
Germany
VDI3940 Method is applied by Germany, It is also called Determination of Odorants in
Ambient Air by Field Inspections.
 < 10 percent of odour hours of residential areas
 <15 percent of odour hours of non – residential areas
United Kingdom

11. They Implement the Environment Protection Act which covers IPC (Integrated pollution and
control) and LAAPC (Local authority pollution control). IPC policy covers the control for
the complex polluting processes with emission to water, land and air while LAAPC covers
the control for small process with emission restraining to air only.
8. RECOMMENDATION
I. There is requirement for data based information on the magnitude of odorous
chemicals or gases at the ambient environment as well as at point source
II. The report provided by the expert committee should be followed as guidelines for
odour control.
III. Management practices or Pilot practices should be done to control odour pollution and
should be sector wise. Additionally, such practices should be financially assisted if
required.
IV. Green belts should be adopted to control the odour pollution created near waste
disposal sites and industrial processing areas. The green belts should be equipped with
suitable species of trees and plants and other physical methods can also be adopted if
required.
V. The Human Resource working in this sector should be exposed to international Odour
pollution control and should provide assistance for the same
VI. According to the source of the odour emission, standards should be formed for
example, Pesticides, Chemical, Fertilizer, Drugs & Pharmaceuticals, Waste water
treatment etc.
VII. For developing an effective control system on odour pollution, it is vital that the
measurement on odour is done in such a way that it is accurate, acceptable and
precise.
VIII. The areas where there is more pollution related to odour should be tackled first with
the technology and knowledge presently held by the country
IX. The standards for pollution should be updated from time to time
X. Efforts should be exerted to maintain and operate the dump sites, treatment plants, air
pollution control device etc. so as to reach an optimal reduction in odour pollution
9. BIBLIOGRAPHY
 www.epd.gov.hk/epd/english/greenproperty/poll_pro/poll_pro_rec.html
 www.eolss.net/sample-chapters/c09/e4-11-02-00.pdf
 www.sinia.cl/1292/articles-
55384_Strategy_Odors_Management_2014_2017.pdf
 cpcb.nic.in/upload/NewItems/NewItem_141_package_odourreport_2.12.08.
pdf