Date: July 21, 2009

To: Jeff Telander, EPA/OAQPS/SPPD

From: Rick Marinshaw, RTI International

Subject: Rationale for Establishing Work Practice Standards for Periodic Brick Kilns

I. Overview of Periodic Kilns

Periodic kilns are batch process units that are used for firing brick and structural clay 

products (BSCP) under a carefully-controlled environment. The large majority of BSCP are 

fired in tunnel kilns, which operate continuously and are much more energy-efficient than 

periodic kilns when producing BSCP of a uniform type, such as standard building bricks. The 

main advantage of periodic kilns is that they can readily accommodate variations in firing 

temperature profiles and cycle times to match the requirements of a wide variety of products. As

a result, periodic kilns generally are reserved for specialty products and typically are used only 

when necessary.

In the BSCP industry, periodic kilns are classified as either beehive kilns or shuttle kilns, 

but all operate generally the same. A batch of unfired bricks or shapes is loaded into the kiln, the 

kiln is sealed, and the burners are ignited and controlled to carefully increase the temperature 

according to a time-temperature profile specific to the products being manufactured. Once firing 

is complete, the temperature in the kiln is reduced, the burners are extinguished, and the fired 

product is allowed to cool. When the product is at or near ambient temperature, the kiln is 

opened, and the fired products are removed.

The U.S. Environmental Protection Agency (EPA) conducted an information collection 

effort in 2008 to update information on the inventory of affected units, hereafter referred to as 

“the 2008 EPA survey.” Based on the responses to the 2008 EPA survey for the BSCP industry, 

periodic kiln cycle times range from 35 to 168 hours per cycle, and typically take 48 to 58 hours. 

These cycle times cover the period beginning when the burners are first ignited and ending when 

the burners are cut off (Belden, 2008; Blankenbeker, 2008; Krzyzanowski, 2008; Pence, 2008). 

It may take an additional 8 to 10 hours for the fired products to cool before they can be removed 

from the kiln.
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II. Periodic Kiln Emissions

Based on data from the testing of three periodic BSCP kilns using Method 320 (Fourier 

transform infrared [FTIR] spectroscopy), emissions of hydrogen fluoride (HF) and hydrochloric 

acid (HCl) begin within the first 5 to 10 hours of the firing cycle and continue throughout the 

firing cycle (Western Environmental, 2003a; Western Environmental, 2003b; Western 

Environmental, 2008). Figures 1 through 3 depict the HF and HCl emission concentrations and 

kiln temperatures as a function of time for these tests. As indicated in the figures, emissions are 

highly variable and can experience large spikes at various points throughout the cycle. In 

addition, it is likely that emissions continue beyond the completion of the firing cycle, as the 

fired products cool. For example, Figure 1 shows that HF concentrations in the kiln exhaust can 

still exceed 100 parts per million at the end of the firing cycle.
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HF Emissions -- Acme (Bridgeport) Periodic Kiln #3

0

50

100

150

200

250

0

2

35

68

10

1113

14

1617

1921

23

2426

2732

33

3537

3840

41

4347

48

Cumulative Hours from Start of Cycle

HF concentration (ppm)

0

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600

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1200

1400

1600

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2000

Temperature (F)

Temperature

HF Concentration

HCl Emissions -- Acme (Bridgeport) Periodic Kiln #3

0.0

10.0

20.0

30.0

40.0

50.0

60.0

023568

10111314161719212324262732333537384041434748

Cumulative Hours from Start of Cycle

HCl Concentration, ppm

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Temperature (F)

Temperature

HCl Concentration

Figure 1. HF and HCl Emissions for Periodic Kiln, Acme Brick, Bridgeport, Texas

(Western Environmental, 2003b).
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HF Emissions -- Acme Milsap Round Kiln

0

50

100

150

200

250

300

023579

10121415171921232526283032343537394042444950

Cumulative Hours from Start of Cycle

HF Concentration (ppm)

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Temperature (F)

Temperature

HF Concentration

HCl Emissions -- Acme Milsap Round Kiln

0

10

20

30

40

50

60

023579

10121415171921232526283032343537394042444950

Cumulative Hours from Start of Cycle

HCl Concentration (ppm)

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Temperature (F)

Temperature

HCl Concentration

Figure 2. HF and HCl Emissions for Periodic Kiln, Acme Brick, Milsap, Texas (Western 

Environmental, 2003a).
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HF Emissions -- Acme Ft. Smith

0

10

20

30

40

50

60

70

80

90

02468

101214161819212425272931333537394142444648505254

Cumulative Hours from Start of Cycle

HF Concentration (ppm)

0

500

1000

1500

2000

2500

Temperature (F)

Temperature

HF Concentration

HCl Emissions -- Acme Ft. Smith

0

1

2

3

4

5

6

7

02468

101214161819212425272931333537394142444648505254

Cumulative Hours from Start of Cycle

HCl Concentration (ppm)

0

500

1000

1500

2000

2500

Temperature (F)

Temperature

HCl Concentration

Figure 3. HF and HCl Emissions for Periodic Kiln, Acme Brick, Ft. Smith, Arkansas

(Western Environmental, 2008).

III. Testing Periodic Kilns for Emissions of HF and HCl

The conventional compliance test requirement for most emission sources is to test each 

source for three 1-hour test runs. This requirement is based on the assumptions that the source 

operates continuously and that emissions are relatively constant. However, there generally are 

some variations in emissions. For this reason, the source is tested over three separate runs and 

the results are averaged to generate a number that is representative of typical emissions.
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Unlike continuous sources, emissions from periodic BSCP kilns can vary significantly 

over the course of one cycle. Because of these variations, and the fact that emissions begin 

shortly after the start of the firing cycle and continue beyond the end of the cycle for an 

undetermined period of time, the conventional compliance test requirement of three 1-hour test 

runs is not an option. Instead, the only way to accurately determine the total emissions from a 

periodic BSCP kiln cycle is to measure the emissions throughout the entire firing cycle and 

continuing beyond the completion of the cycle until emission levels become negligible. Testing 

for any less time could result in estimated emissions that either are much higher or much lower 

than actual emissions, depending on when during the kiln cycle emissions are sampled.

Because of the variations during firing cycles and variations across the tests represented 

by Figures 1 to 3, sampling a single kiln cycle might not be adequate for characterizing periodic 

kiln emissions. For the BSCP industry, that would mean testing each periodic kiln for more than 

100 hours in order to determine an emission rate that is representative of normal operating 

conditions. Furthermore, because periodic kilns are used to fire specialty products that may have 

significantly differently time-temperature profiles, it may be necessary to test the same kiln 

multiple times to characterize emissions from different types of products.

IV. Test Methods

The standard reference methods for measuring emissions of HF and HCl are EPA 

Methods 26 and 26A. These methods are reliable and relatively inexpensive. However, if 

emissions are variable and experience large spikes, as appears to be the case for BSCP periodic 

kilns, breakthrough of HCl can occur. That is, the testing apparatus reaches its capacity for 

absorbing HCl, and subsequent HCl in the emissions are not captured. It is not known if 

breakthrough has occurred until a breakthrough analysis is performed after completion of the 

test. If it is determined that breakthrough has occurred, retesting is necessary. Another 

disadvantage to using Methods 26 or 26A for testing throughout periodic kiln cycles is the need 

for additional manpower to operate the sampling trains around the clock and to recover samples.

The alternative to using Methods 26 or 26A is to conduct the tests using FTIR according 

to EPA Method 320. With FTIR, HCl breakthrough is not an issue. In addition, FTIR also 

provides near real-time emissions data, and the cost for testing by FTIR would not be 

significantly different than the cost for testing by Methods 26 or 26A throughout an entire cycle.

For these reasons, testing by FTIR is the only practical method for accurately measuring HF and 

HCl emissions from periodic BSCP kilns.

V. Emission Test Costs

The cost for testing by FTIR is estimated to be $49,750 for a single 50-hour kiln cycle

(DeWeese, 2009). If it were determined that the variations in emissions from cycle to cycle were 

significant, it might be necessary to test each kiln for two cycles in order to develop a 

representative emission rate. Doing so would double the testing costs to almost $100,000. In 

addition to these costs, additional costs would be incurred for testing the kilns for particulate 

matter (PM) emissions, which would have to be tested using a manual test method (e.g., EPA 

Methods 5 or 17). If testing were extended into the cooling period, the costs would be even 

higher.
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VI. Technical and Economic Feasibility of Numerical Emission Limits for Periodic 

Kilns

As stated in section 112(h)(1) of the Clean Air Act, work practice standards or other 

requirements can be prescribed in lieu of a numerical emission limit if the Administrator 

determines that a numerical emission limit is not feasible. Section 112(h)(2)(B) further defines 

the term “not feasible” in this context to apply when “the application of measurement technology 

to a particular class of sources is not practicable due to technological and economic limitations.”

To evaluate the feasibility of establishing a numerical emission limit for BSCP periodic 

kilns, the estimated average testing cost for HF and HCl emissions by FTIR for a single 50-hr 

kiln cycle (i.e., $49,750 per kiln) was compared to sales data for the 97 periodic kilns located at 

BSCP facilities that would be subject to the NESHAP (Walton, 2009). This analysis indicated 

the cost-to-sales ratio ranged from less than 1 percent to more than 700 percent. Cost-to-sales 

would be at least 3 percent for 53 of the 97 periodic kilns, and would be at least 10 percent for 48 

of the 97 kilns. When compared to typical profits, cost-to-profit would be at least 10 percent for 

89 of the 97 periodic kilns, at least 50 percent for 34 of the 97 kilns, and more than 100 percent 

for 3 of the kilns. If the additional costs for PM testing, extending the HF/HCl testing into the 

cooling period, or testing for two cycles are included, the cost-to-sales and cost-to-profit ratios 

would be even higher.

Based on these findings, it is concluded that it is not feasible to establish numerical 

emission limits for periodic BSCP kilns because of the technological and economic limitations 

described above. Demonstrating compliance with a numerical emissions limit for periodic kilns 

is technologically limited to testing procedures that are economically infeasible for the BSCP 

industry.

VII. References

Belden, B. 2008. “ICR - Brick & Structural Clay Products (Belden Brick).” E-mail and 

attachment from Bradley Belden, Belden Brick Co., to Jeff Telander, EPA/OAQPS/SPPD

containing response to Section 114 request for the BSCP industry. August 13, 2008.

Blankenbeker, S. 2008. “EPA Brick Info.” E-mail and attachment from Steve Blankenbeker, 

Taylor Clay Products, to Jeff Telander, EPA/OAQPS/SPPD containing response to Section 

114 request for the BSCP industry. August 14, 2008.

DeWeese, J. 2009. “Re: Discussion Of Test Methods and Costs For Brick Kilns.” Email and 

attachment from Jason DeWeese, EPA/EMAD, to Jeff Telander, EPA/SPPD. April 16, 2009.

Krzyzanowski, M. 2008. “USEPA Information Survey HAP Emission Sources & Controls -

BSCP Industry.” E-mail and attachments from Mike Krzyzanowski, Glen-Gery Corp., to 

Jeff Telander, EPA/OAQPS/SPPD containing response to Section 114 request for the BSCP 

industry. August 13, 2008.

Pence, J. 2008. “Acme Brick Company - ICR.” E-mail and attachments from Jason Pence, 

Acme Brick Co., to Jeff Telander, EPA/OAQPS/SPPD containing response to Section 114

request for the BSCP industry. August 13, 2008.
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Walton, T. 2009. Economic Feasibility of Testing Periodic Brick Kilns. Memorandum from 

Tom Walton, EPA/ABCG, to Jeff Telander, EPA/SPPD. July 15, 2009.

Western Environmental (Western Environmental Services and Testing, Inc.). 2003a. Acme 

Brick Company, Milsap, Texas, Emissions Testing: Round Kiln Stack. February 12 through 

14, 2003. File Number 03-8004.

Western Environmental (Western Environmental Services and Testing, Inc.). 2003b. Acme 

Brick Company, Bridgeport, Texas, Emissions Testing: Periodic Kiln #3 Stack. May 21 

through 23, 2003. File Number 03-8014.

Western Environmental (Western Environmental Services and Testing, Inc.). 2008. Acme Brick 

Company, Fort Smith, Arkansas, Emissions Testing: Kiln 1 Stack. December 10 through 12, 

2003. File Number 03-8029. Revised January 21, 2008.