DAQ-2024-008500

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June 14, 2024

Ryan Bares
Division of Air Quality
PO Box 144820
Salt Lake City, UT 84114-4820
[e-mail]

Re: Public Comment on R307-315 and R307-316 NOx Emission Controls for Natural Gas-Fired Boilers 2.0-
5.0 MMBtu and Natural Gas-Fired Boilers Greater Than 5.0 MMBtu

Dear Mr. Bares,

A. O. Smith Corporation (“A. O. Smith” or “Company”) appreciates the opportunity to provide
comments on the Division of Air Quality (“Division”) proposed rules R307-325 NOx Emission Controls for
Natural Gas-Fired Boilers 2.0-5.0 MMBtu and R307-316 NOx Emission Controls for Natural Gas-Fired
Boilers Greater Than 5.0 MMBtu (“Proposed Rules”) and looks forward to continuing to be a resource to
the Division.

About A. O. Smith

A. O. Smith Corporation, with global headquarters in Milwaukee, Wisconsin since 1874, applies
technology and energy-efficient solutions to products manufactured and marketed worldwide with
operations in the U.S., Canada, China, India, Mexico, the Netherlands, and the UK. Listed on the New
York Stock Exchange (NYSE: AOS), the Company is one of the world’s largest manufacturers of
residential and commercial water heating equipment and boilers, as well as a leading manufacturer of
water treatment and air purification products. Along with its wholly owned subsidiaries, A. O. Smith is
the largest manufacturer and seller of residential and commercial water heating equipment, high
efficiency residential and commercial boilers, and pool heaters in North America.

Overview

The Company appreciates the work of the Division in the initial update to these rules, however it
questions the benefits of adding a carbon monoxide (“CO”) limit to the requirements. A typical ultra-low
NOx boiler will operate well under the proposed 200 ppm CO limit during standard operation and will
not surpass 200 ppm CO in its normal operation. Additionally, the Company’s products undergo a series
of rigorous tests to meet performance and safety requirements. One such certification is the CSA/ANSI
Z21.13 safety certification, which covers CO emission limits for the boiler. If the Division chooses to
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adopt its proposed CO limit requirement within the proposed rules the Company would strongly
recommend that a final limit align with existing industry standards. A 400-ppm level would harmonize
Utah’s rules not only with the existing safety standards but also with air quality districts that choose to
regulate CO emissions.

Carbon Monoxide Limit

Under Bay Area Air Quality Management District (“BAAQMD”) Rule 9-7: Nitrogen Oxides and
Carbon Monoxide from Industrial, Institutional And Commercial Boilers, Steam Generators And Process
Heaters, BAAQMD sets a CO emission for every size of boiler at 400-ppmv dry at 3% O2.1 Additionally,
South Coast Air Quality Management District (“SCAQMD”) sets for Rules 1146 and 1146.1 pertaining to
Commercial Boilers between 2.0-5.0 MMBtu and greater than 5.0 MMBtu.2,3 These rules also set a CO
emissions limit of 400-ppmv dry at 3% O2. Alignment with these standards would meet the goals of the
state while also limiting the required certifications need for ultra-low NOX product lines.
Moreover, the Company observes that while most boilers typically operate at or under 100-ppm
CO at 3% O2, the products are not tested or certified for operation at that limit. The CO limit applied for
safety certification according to CSA/ANSI Z21.13 is 400-ppm CO at 3% O2. As such, all boilers certified
to those standards are verified to safely shut down under any adverse operating condition that could
produce more than 400-ppm CO. Conversely, boilers are not designed, tested, or certified to meet a
200-ppm CO limit. This new requirement will add unnecessary burden to manufactures of retesting and
recertifying products to meet a standard that will have minimal, if any, true emissions saving compared
to existing standards and certification. Given this the Company recommends that the current limit of
200-ppm CO at 3% O2 be increased to 400-ppm CO at 3% O2.

Timing

As previously stated, products are not currently certified to an emissions rate of 200-ppm.
Hence, if the Division moves forward with these new requirements manufacturers would have to test
and recertify all existing ultra-Low NOx product lines sold into the state. This would require a significant
investment and time committed to in-house and third-party testing. Given this, it is unreasonable to
expect manufacturers to meet the required compliance deadline in the rule of May 1, 2024. If the
Division chooses to move forward with the rule as proposed, at least 3 years would be required to retest
and certify all ultra-low NOx product offerings to a 200-ppm limit, and the Company requests that the
Division adopt a compliance deadline of 3 years after the publication of the final rule if a 400-ppm limit
is not adopted in line with existing state regulations and safety standards.

Conclusion

1 https://www.baaqmd.gov/~/media/dotgov/files/rules/reg-9-rule-7-nitrogen-oxides-and-carbon-monoxide-from-
industrial-institutional-and-commercial-
boiler/documents/rg0907.pdf?rev=ab95f36c2dd146528f1cf3c10596bce3&sc_lang=en
2 https://www.aqmd.gov/docs/default-source/rule-book/reg-xi/rule-1146-1.pdf?sfvrsn=4
3 https://www.aqmd.gov/docs/default-source/rule-book/reg-xi/rule-1146.pdf?sfvrsn=4
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For the reasons cited above, the Company encourages the Division to reconsider the Proposed
Rule and replace the 200 ppm CO emissions requirement with the requirement that Natural Gas-Fired
Boilers meet an emissions rate of CO less than 400 ppm, in line with the requirements of ANSI/CSA
Z21.13, BAAQMD 9-7, and SCAQMD 1146 and 1146.1. A. O. Smith looks forward to working with the
Division as it further considers its Proposed Rule.

Best Regards,

Kyle Bergeron
Manager, Government and Regulatory Affairs
A. O. Smith Corporation
Global Headquarters
11270 West Park Place
[phone]
[e-mail]