Louisiana Administrative Code
Title 33 - ENVIRONMENTAL QUALITY
Part III - Air
Chapter 29 - Odor Regulations
Section III-2901 - Odorous Substances
Universal Citation: LA Admin Code III-2901
Current through Register Vol. 50, No. 9, September 20, 2024
A. Purpose. The purpose of this Chapter is to establish an ambient air standard for odors.
B. Scope. This Section is applicable to all sources which emit odorous substances into the ambient air except those exempted in LAC 33:III.2901.E.
C. Definitions
Odor Dilution Ratio-the dilution of a sample required to reach a given odor intensity level, detectability point, sensory target, etc. This is represented by Zt.
Zt = Co/Ct
where:
Co = the odorant concentration (of the sample); and
Ct = the odorant concentration when some sensory target has been reached, such as the odor threshold.
Perceived Odor Intensity-the intensity of an odor sensation which is independent of the knowledge of the odorant concentration.
D. Standard. Limit on Odorous Substances at or beyond Property Lines. A person shall not discharge an odorous substance which causes a perceived odor intensity of six or greater on the specified eight point butanol scale when determined by the department's test method. (Method 41)
E. Exemptions. The following buildings, materials and operations are exempted from the provisions of this regulation:
1. single
family dwellings;
2.
restaurants;
3. other
establishments for the purpose of preparing food for human
consumption;
4. materials odorized
for safety purposes;
5. materials
possessing strong odors for reasons of public health and welfare where no
suitable substitute is available and where best modern practices are
employed;
6. agricultural, fiber,
timber, poultry, seafood or fisheries production, unless such odors are
detected in concentrations or intensities above that normally detected from
these processes or byproducts when using applicable air pollution control
devices; and
7. emission points
regulated under the Total Reduced Sulfur (TRS) emission standard (LAC
33:III.2301.D.3).
F. Sample Analysis
1. Collection of Samples.
Samples shall be taken and transported in a manner which minimizes alteration
of the samples either by contamination or loss of material.
2. All samples shall be evaluated as soon
after collection as possible in accordance with the procedures set forth in
Subsection G of this Section.
G. Method 41-Odor Test Methods
1. Butanol Odor Evaluation Procedure
a. Sampling and Storage. Odorous gas sampling
is no more than typical integrated bag sampling. Figure l shows the sampling
train used by the department. A sample bag is placed inside the rigid
leak-proof container. Bag material shall be manufactured of FEP Teflon, Tedlar,
or Mylar.
b. The bag is filled by
partially evacuating the rigid container. After partial filling, the air in the
bag is expelled by pumping air into the container until the bag is empty. This
serves to precondition the bag walls.
c. The bag is then totally filled by
evacuating the container with a pump. The bag is removed, capped or sealed, and
tagged for storage and eventual transport to the odor lab for sample
evaluation. See Figure l for apparatus setup.
d. If the odorous air is very humid, and it
is suspected that condensation of water will occur in the bags, an additional
procedure, predilution, can be used to prevent condensation. The bag is half
filled with odor-free air using a cylinder and flowmeter. This will allow exact
metering of a known amount of odor-free air; the odorous air sample can then be
taken per previous instructions.
e.
Odorous samples should be stored in containers for a minimum of time after
collection. This should be adhered to wherever possible and the time of
storage, before odor measurement, must be recorded for each sample. Ideal
storage conditions are less than four hours; acceptable conditions for most
odor mixtures are 8-16 hours. Storage over 24 hours is unacceptable. In
general, to prevent sample deterioration:
i.
use FEP Teflon, Tedlar, or Mylar bags;
ii. minimize sample storage time;
and
iii. predilute sample bag or
use other suitable means to remove moisture if condensation is evident on the
bag wall.
2.
The department uses butanol referencing techniques for quantifying odors in
terms of intensity. The method parallels that specified in ASTM E544-75. A
complete description of the method follows.
a. Description
i. Figure 2 depicts the olfactometer.
Adjustable air flow controls are mounted on the rectangular base plate. The
odorant vapor generator, flow splitters, and ports that deliver the prepared
stimuli (butanol) are mounted on an aluminum plate disc that can be rotated
within an almost full revolution. A handle is positioned to turn the sample
ports and is set to limit the rotation of the disc to one turn.
ii. There are two air flow systems within the
olfactometer, each is controlled by a separate valve (V) and monitored by
separate in-line flowmeters (F1,
F2). Both can be supplied from the same air
supply.
iii. Odorant vapor flow
system is supplied with air at a rate of 350 ml/min (left flowmeter). This air
flow is delivered to the odorant vapor generator through a flexible food-grade
(almost odorless) Tygon tubing (T). The odorant vapor generator consists of a
glass vessel (G) and several flow-controlling capillaries. This section is
shown separately schematically in Figure 3.
iv. The odorant vapor/air mixture from the
generator is supplied to the upper cavity of the "odor splitter" (O) through
the upper tubular spout of this splitter. The splitter distributes the
generator-prepared vapor/air mixture to eight stainless steel capillaries. The
other ends of the capillaries connect via Teflon tubing to the corresponding
glass sniffing ports. The capillaries are calibrated so that Port Number 8
(highest odorant concentration) receives mominally 160 ml/min of the vapor/air
mixture, and the next Port, Number 7, receives nominally 80 ml/min of the same
mixture. Other ports receive odorant volumes as per Table l.
v. The make-up air flow system, which is
controlled by the valve-Flowmeter assembly (F2), is fed
at 950 ml/min. It is distributed by the lower level of the splitter (O). The
make-up air is delivered to this level via Tygon tubing attached to the spout
of the splitter under the olfactometer disc. There is no connection between the
lower level and upper level of the splitter. The lower splitter provides
additional air to Ports Number 7 through Number 1 so that the total flow to
each port is nominally 160 ml/min. Mixing occurs in the port. Rapid flow rate
changes occur on emergence from the Teflon tubing and from the lower smaller
cross section of the glass port into the wider vertical glass tube portion.
This action assures sufficient turbulence for adequate mixing.
(a). Flow rates are measured, if necessary,
by attaching a Buck Calibrator flowmeter to ends of the Teflon tubings
temporarily pulled out of the ports. Nominal flow rates should be:
|
Table 1 |
||
|
Odorant Vapor-Carrying Tubing End |
Make-Up Air |
|
|
Port Number |
Tubing End (ml/min) |
Tubing End (ml/min) |
|
8 |
160 |
|
|
7 |
80 |
80 |
|
6 |
40 |
120 |
|
5 |
20 |
140 |
|
4 |
10 |
150 |
|
3 |
5 |
155 |
|
2 |
2.5 |
157.5 |
|
1 |
1.25 |
158.5 |
(b).
The actual flow rates may differ, usually not more than within a few percent,
and are measured and included in calculations in more exact
experiments.
vi. Vapor
generator section, Figure 3, contains a saturator, (Vessel G) which consists of
a horizontal 16 mm o.d. by 170 mm long Pyrex tube with closed ends and three
side tubes, each 4 mm o.d. and 25 mm long. The middle tube is used to introduce
the odorant (butanol) and is then closed with a glass rod plug, P, connected to
the side tube by a short length of black neoprene tubing.
vii. Important Safety Note. When slipping the
neoprene tubing onto the glass side tubes, hold the side tube with fingers
using short neoprene tubing collar with which the tube is equipped. Twist the
attachable neoprene tubing to and fro, to facilitate the connection. If the
glass vessel is held instead, the small glass side tubes may break off. Use the
same precautions when removing the attachable tubing. Same applies to the other
glass tubing/neoprene slip-on connections. Collars are not shown in Figure
3.
viii. The two other glass side
tubes on the vessel are connected to the flow control capillaries. Capillary C
is the principal vapor flow control capillary, while Capillary E is simply an
exit capillary, with much less flow resistance than C. Capillary B is for air
bypass; it is always of the same size and length, while Capillary C may be
changed to provide 5x, 25x, 50x, and 100x flow split ratio. The department will
use the nominal 5x flow split ratio in establishing its butanol scale. The
ratio of flow rates through bypass B and through the saturator vessel vapor
space depend on the flow resistances of B and C. Capillary C is upstream of the
vapor space to maintain air pressure in the saturator vessel close to
atmospheric.
ix. The desirable
volume of odorant in the saturator vessel is 8-10 ml, which fills the lower
half of the vessel and provides the widest surface. At up to 60 ml/min air
flow, the air leaving the saturator is practically saturated with the odorant
vapor, as has been established by mass-transfer calculations and direct
measurements of l-butanol concentrations by hydrogen flame ionization detector;
at 60 ml/min, 98 percent plus saturation is reached. The degree of saturation
is not a function of the vapor pressure (which varies with odorants by several
orders of magnitude), but of the diffusion constant for the odorant in air, and
this constant varies from odorant to odorant within a fraction of one order of
magnitude. The method of air passage over the surface circumvents the need for
mist filters needed when the saturation is by bubbling the air through the
odorant. At lower flow rates, a few drops of the odorant may provide enough
evaporation surface.
x.
Vaporization rates are too low to produce significant cooling except for the
most volatile odorants. Hence, for simplicity, no thermostating is provided,
but the temperature at the saturator vessel is measured for use in vapor
pressure calculations. The temperature in the area of the apparatus will be
maintained at 25°C.
xi. The vapor
dilution immediately after the saturation in the vessel produces a margin of
safety in preventing condensation in the 8-way splitter, in case of a
temperature change or sudden pressure drop.
xii. Connections to the stainless steel
capillaries are via slip connectors, as shown in Figure 3. A short (5 MM)
length of food-grade Tygon tubing fits tightly around the Capillary. A piece of
black neoprene tubing overlaps this tubing and the larger connecting tube
(brass tee, or glass side tube, or multi-way air or odorant-side splitter) so
that the small Tygon tubing fits tightly against the larger tube. This system
permits only a limited contact between the odorant vapor and Tygon and
neoprene. These materials can be reached by vapors only by a non-connective
diffusion through stagnant annular space between the o.d. of the capillary and
the larger connecting tube; thus, depletion of vapor by sorption into Tygon or
neoprene is negligibly small. In reverse, when the odorant vapor is
discontinued, contamination of air flow by desorption of the odorant from Tygon
or neoprene is slow and usually does not generate a prolonged contamination
problem of any significance. Still, it is desirable to flush the odorant vapor
flow system during the shutdown.
xiii. Connections between B and E Capillaries
are via brass tees and slip on connectors. To check the generator system
splitter ratio, brass tee (T) is pulled off B and E, and the flow rates out of
B and E are measured using the same total odorant vapor flow rate as normal
(the splitter ratio may be slightly affected on the absolute flow
rates).
xiv. Important-only soap
film flowmeters are suitable for measuring the flow rates in ports and at B and
E. Other flowmeters produce some flow resistance which, in the low-pressure
flow system of the olfactometer, will influence the flow rates and yield wrong
values. Figure 3, bottom, illustrates connections to the soap film flowmeter
for two situations:
(a). connecting to Teflon
tubing ends pulled backward out of the ports for measuring flow rates to the
ports; and
(b). connecting to ends
of B or E when the brass Tee (Figure 3) is pulled off for measuring the flow
rates from B and E, to check split ratio in the vapor generator
section.
xv. Very
Important-to Prevent Undesirable Contamination of the System
(a). With the odorant in the vapor-generating
vessel, the flow of air to the odorant part of the system must be immediately
set in operation. If this is not done, odorant vapors from the vessel may drift
into the splitter bypass, condense there, and result in a much higher odorant
concentration than in the regular operation. It is best to place the odorant
into the vessel through the center spout (cf. Figure 3) with the bypass system
(two brass tees with Capillaries B, C, and E attached) removed from the vessel,
then plug the center spout of the vessel, begin air flow and then connect the
bypass system to the vessel.
(b).
The same applies to shutting-down of the olfactometer. First, the by-pass
system is removed from the vessel, and the end spouts of the odorant vessel are
plugged with pieces of neoprene tubing and glass rod plugs. With air flow still
continuing, the Capillary C is connected to Capillary E by a short piece of
Teflon tubing. This permits flushing the odorant vapors from the odorant side
of the system. Flushing is continued until the highest-concentration port does
not exhibit odor.
3. Problems/Backflow. Failure to observe need
for continuous air flow while the odorant vessel is connected to the splitter
(see preceding section) can easily result in diffusion of the odorant
throughout the system, including back-diffusion into the Tygon tubing
connecting flowmeter to the disc assembly. Such contamination is difficult to
remove, and replacement of some components may become necessary. A list of
sources for the components is attached (Paragraph G.5 of this
Section).
4. Sample Calculation of
Dilutions
a. Saturated Butanol
i. Odorant: l-Butanol
ii. Temperature: 25°C
iii. Vapor pressure, from Chemistry and
Physics Handbook or other source, for 25°C is 6.97 mm.
iv. This corresponds to:
l,000,000 x 6.97/760 = 9170 ppm in air saturated with l-butanol vapor at 25°C; (l atm = 760 mm).
b. Dilution Factor in Generator/Bypass
System. Dilution Factor: 4.66 +- .20
i. The
concentration of l-butanol in the flow supplied to the round splitter is then:
9170/4.66 = 1966 +- 16 ppm
ii. This is also the concentration supplied
to Port Number 8.
iii. Measurements
for other ports are conducted by pulling the Teflon tubing out from the ports
and connecting the Buck calibrator to these lines.
iv. The following set of data illustrates the
calculations. (See Table 2)
v. The
brass tee is sequentially pulled off Capillaries B and E and the air flow from
each is measured.
5. Components and Sources
a. Stainless Steel Capillaries
i. l/16 o.d., 0.030 i.d.
ii. l/16 o.d., 0.020 i.d.
iii. l/16 o.d., 0.010 i.d.
b. Teflon Tubing. Teflon tubing AW
Gage Number 15, standard wall, natural color.
c. Tygon Tubing
i. Tygon Food Grade 0.0315 in. i.d. For
slip-on-connectors for stainless steel capillaries.
ii. Tygon tubing, Food Grade Formulation
B-44-4X, 5/32 in. i.d., 7/32 in. o.d., l/32 in. wall. For flowmeter-to-disc
connection.
iii. Tygon Food Grade
tubing, 0.0655 in. i.d., 0.1945 in. o.d. For connection of soap film flowmeter
tubing to Teflon tubing ends.
d. Neoprene Tubing. Black neoprene tubing,
l/4 in. o.d., l/16 in. wall, for slip-on connectors and for plug.
e. Glass Ports, Odorant Vessel. Pyrex glass,
custom-made by glass blowers.
f.
Flowmeters
i. 50-500 cc/min
ii. 100-1000 cc/min
|
Table 2 8-Port 1-Butanol Olfactometer Port Concentration in ppm |
|||||||
|
Date |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
|
12-13 |
1038 |
533 |
274 |
138 |
70 |
35 |
17 |
|
12-15 |
1034 |
517 |
272 |
137 |
71 |
34 |
18 |
|
12-15 |
1042 |
524 |
268 |
137 |
71 |
34 |
19 |
|
12-15 |
1042 |
520 |
271 |
132 |
72 |
35 |
18 |
|
12-16 |
1010 |
513 |
271 |
136 |
70 |
35 |
17 |
|
12-16 |
1040 |
529 |
278 |
137 |
73 |
36 |
18 |
|
12-16 |
1032 |
516 |
272 |
134 |
72 |
35 |
18 |
|
Total |
7238 |
3652 |
1906 |
951 |
499 |
244 |
125 |
|
Avg. |
1034 |
522 |
272 |
136 |
71 |
35 |
18 |
|
+-10 |
+-7 |
+-3 |
+-2 |
+-1 |
+-1 |
+-1 |
|
6. Odor Panel
a. An odor panel consisting of eight members
shall be selected by the department. Panelists shall not use perfume or
perfumed shaving lotion within two hours prior to the test. Panelists shall not
smoke, eat, or chew tobacco or gum for at least one hour before testing.
Panelists shall not be tested for prolonged periods of time. A loose schedule
with long resting periods for panelists is recommended.
b. Panelist candidates are screened for their
ability to judge intensity. This is usually done using the butanol intensity
olfactometer. A bag sample is taken from one of the eight butanol ports
(usually Number 4 or Number 5) and the candidate must sniff the bag sample and
select the port they feel has the same intensity. Panelists should be able to
match butanol-to-butanol within two scale units. As with all sensory odor
evaluations, the screening tests should be conducted in as nearly an odor-free
environment as possible.
c. The
testing room will be supplied with activated carbon filtered air of controlled
constant temperature and humidity (25°C and RH 50 percent).
d. Each panelist compares the intensity of
the undiluted ambient sample being evaluated to the eight point butanol scale,
specified in this procedure starting from the low end of scale, i.e., levels
between two values on the scale may be selected by each panelist (i.e., 2.5,
6.5, etc). The arithmetic average of the values chosen by the eight panelists
will determine compliance with the standard specified in the regulations.
AUTHORITY NOTE: Promulgated in accordance with R.S. 30:2054.
Disclaimer: These regulations may not be the most recent version. Louisiana may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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