SAN DIEGO COUNTY AIR POLLUTION CONTROL DISTRICT
RULE 67.24 - BAKERY OVENS
(Adopted & Effective: 6/7/94: Rev. Adopted & Effective 5/15/96)
Except as provided in Section (b), this rule is applicable to bakery ovens which emit volatile organic compounds
(VOC's) during the baking of yeast-leavened products.
Bakery ovens subject to this rule shall not be subject to Rule 66.
(b) EXEMPTIONS (Rev. Effective 3/7/95)
- The provisions of this rule shall not apply to bakery ovens which are located at a stationary source where
the combined rated heat input capacity of all bakery ovens is less than 2 million British Thermal Units (BTU) per
It shall be the responsibility of any person claiming the exemption in Subsection (b)(1) to provide information
necessary for the District to determine the combined rated heat input capacity of all bakery ovens. Such information
may include oven or burner manufacturer specifications, or may include fuel or energy consumption rates for oven
start-up period(s) in cases where manufacturer specifications are unavailable.
- The provisions of this rule shall not apply to ovens used exclusively for the baking of products leavened chemically
- The provisions of Sections (d) and (g) of this rule shall not apply to bakery ovens which are located at a
stationary source where the uncontrolled emissions of VOC's from all bakery ovens combined is less than 50 tons
per calendar year.
(c) DEFINITIONS (Rev. Effective 5/15/96)
For the purposes of this rule, the following definitions shall apply:
- Bakery Oven means an oven which bakes yeast-leavened products, including but not limited to breads,
buns, and rolls.
- Combustion Stack means a stack on a bakery oven which emits exclusively combustion exhaust gases
which do not pass through the oven's baking chamber.
- Comfort Hood Vent means a vent or hood used to control air flow outside the entrance or exit
of a bakery oven.
- Exempt Compound means the same as defined in Rule 2. (Rev. Effective 5/15/96)
- Fermentation Time means the elapsed time between adding yeast to dough or sponge and placing
the dough or sponge into a bakery oven, excluding retardation time, expressed in hours.
- Purge Stack means a bakery oven stack used exclusively for evacuation of residual gases from
the bakery oven during burner ignition.
- Retardation Time means any portion(s) of the elapsed time between adding yeast to dough or sponge
and placing the dough or sponge into a bakery oven, where the dough or sponge is refrigerated at temperatures of
less than 10°C (50°F), for the specific purpose of retarding the fermentation process.
- Stationary Source means the same as defined in Rule 20.1.
- Uncontrolled VOC Emissions means VOC emissions from a bakery oven, before application of add-on
air pollution control equipment or process modification.
- Volatile Organic Compound (VOC) means any compound of carbon, which may be emitted to the atmosphere
during bakery oven operations, except methane, carbon monoxide, carbon dioxide, carbonic acid, metallic carbides
or carbonates, ammonium carbonate, and exempt compounds.
- Yeast Percentage means the pounds of yeast added to a hundred pounds of total flour in the recipe.
- No person shall operate a bakery oven subject to this rule, unless uncontrolled VOC emissions are reduced by
at least 90 percent by weight.
- A person may comply with the requirements of Subsection (d)(1) of this rule by using an air pollution control
(i) has been installed in accordance with an Authority to Construct; and
(ii) includes an emission collection system(s) which ducts the exhaust gases from all stacks, except purge stacks,
combustion stacks, and comfort hood vents, on all bakery ovens to VOC emission control device(s). Such ducting
shall be maintained so as to be free of visible holes, breaks, openings or separations between adjoining components
from which VOC's may be emitted to the atmosphere; and
(iii) has one or more VOC emission control devices, each with reduction efficiency of at least 90 percent by
- A person subject to the requirements of Subsection (d)(2) shall submit an Operation and Maintenance Plan for
the proposed emission control device and emission collection system to the Air Pollution Control Officer for approval,
and receive such approval prior to the operation of the control equipment. Thereafter, the plan can be modified,
with Air Pollution Control Officer approval, as necessary to ensure compliance. Such plan shall:
(i) identify all key system operating parameters. Key system operating parameters are those necessary to ensure
compliance with Subsection (d)(2)(iii) such as temperature, pressure, and/or flow rate; and
(ii) include proposed inspection schedules and anticipated ongoing maintenance regarding the key system operating
- A person subject to the requirements of Subsection (d)(3) shall implement the plan upon approval of the Air
Pollution Control Officer, and shall comply with the provisions of the approved plan thereafter.
After December 7, 1994, a person operating a bakery oven(s) subject to this rule shall maintain records in accordance
with the following:
- Maintain current records necessary to determine VOC emissions for all bakery ovens including, but not limited
to, type of each yeast-leavened baked product, yeast percentage for each product, and fermentation time for each
- Maintain annual records based on calendar year production rates, by weight, of finished baked product for each
- For control equipment, maintain daily records of key system operating parameters specified in Subsection (d)(3)(i),
which will demonstrate continuous operation and compliance of the emission control device during periods of emission
Records maintained in accordance with Subsection (e)(2) are subject to District verification after 60 days following
the end of a calendar year. These records shall be maintained on site for at least three years and shall be made
available to the District upon request.
(f) TEST METHODS
- For the purposes of determining the total annual uncontrolled VOC emissions from a stationary source, VOC emission
factors for each yeast-leavened bakery product shall be determined in accordance with both Table 67.24 and the
EF = 0.95 Yi + 0.19 ti - 0.51S - 0.86 ts + 1.90
Yi = initial yeast percentage
ti = total fermentation time
S = second (spiking) yeast percentage, if applicable
ts = fermentation time for second yeast percentage, if applicable, and
EF = emission factor, pounds of VOC emissions per ton of baked product
Annual uncontrolled emission rates shall be calculated by multiplying emission factors and the annual production
rate for each yeast-leavened finished bakery product. The highest of the two calculated emission rates for a stationary
source shall be used for the purposes of this rule. In cases where annual emissions for a stationary source, as
determined using the highest emission rate, exceed 80 percent of the annual emissions specified in Subsection (b)(3),
or other cases as deemed appropriate by the Air Pollution Control Officer, emission factors shall instead be determined
in accordance with Subsection (f)(2).
Instead of using calculated emission factors, an owner or operatior may elect to use VOC emission factors determined
according to Subsection (f)(2).
- VOC emission factors for yeast-leavened bakery products may be determined by EPA Methods 18, 25, and/or 25A
(40 CFR 60) as they exist on June 7, 1994, together with exhaust flow rates and oven throughputs. Test procedures
shall be performed in accordance with a protocol approved by the Air Pollution Control Officer. An alternative
test method may be used provided such method has been approved, in advance, by the Air Pollution Control Officer,
ARB and EPA.
- Measurement of emission control device reduction efficiency subject to Subsection (d)(2)(iii) of this rule
shall be conducted in accordance with EPA Methods 18, 25, and/or 25A (40 CFR 60) as they exist on June 7, 1994.
Test procedures shall be performed in accordance with a protocol approved by the Air Pollution Control Officer.
(g) COMPLIANCE SCHEDULE
A person operating a bakery oven(s) subject to Subsection (d)(2) of this rule shall meet the following increments
- For an oven which commenced operation prior to June 7, 1994, or for a replacement of such an oven:
(i) By December 7, 1994, submit to the Air Pollution Control Officer any necessary application for Authority
to Construct and Permit to Operate an air pollution control system meeting the requirements of Subsection (d)(2);
(ii) By June 7, 1995, install an air pollution control system pursuant to Subsection (d)(2).
- For an oven which commences operation on or after June 7, 1994, be in compliance with Subsection (d)(1) by
the date of commencement of oven operation.
- For an existing stationary source having a calculated annual emission rate pursuant to Subsection (f)(1) exceeding
80 percent of the emission rate specified in Subsection (b)(3), by August 7, 1994, submit to the Air Pollution
Control Officer for approval a plan for emissions testing pursuant to Subsection (f)(2). Such plan shall provide
for emissions testing to be completed, and test report(s) submitted, by December 7, 1994.
Stationary sources electing to comply with Subsections (d)(2) and (g)(1) shall not be subject to Subsection
*Yt = (Yeast Percentage) x (Fermentation Time)
If yeast is added in two steps,
Yt = (percentage of initial yeast addition) x (time from initial yeast addition to placement
+ (percentage of second yeast addition) x (time from second yeast addition to placement in oven)
** Emission Factor = pounds of VOC per ton of finished baked product