Boiler MACT Rules – Are You in Hot Water?

Boiler MACT Rules

The ‘Boiler MACT’ refers to EPA’s finalized NESHAP (National Emission Standard for Hazardous Air Pollutants) affecting major sources operating a boiler or process heater.  While the NESHAP was finalized in January 2013, it’s the compliance deadlines that began January 31, 2016 that have garnered much attention.

The Boiler MACT rules require owners of Industrial, Commercial, and Institutional Boilers and Process Heaters to not only meet new emissions limits, but also put in place work practices, energy assessments and routine compliance certifications.

Who doe NOT need to be concerned about the Boiler MACT rules?

If your major source boiler/heater is one of the following, your unit is NOT subject to Boiler MACT:

  • Electric utility steam generating unit (EGU) covered by subpart UUUUUof part 63
  • Hot water heaters with a capacity of no more than 120 U.S. gallons or hot water boilers (i.e. not generating steam) with a heat input capacity of less than 1.6 MMBtu/hr (burning gaseous, liquid, or biomass fuel)
  • Waste heat boilers, also known as heat recovery steam generators
  • Boilers used as control devices for other NESHAP standards, where at least 50 percent of the heat input to the boiler is provided by the NESHAP regulated gas stream
  • Research and development boilers
  • Boilers subject to other NESHAP standards/ Section 129 standards/hazardous waste boilers
  • Recovery boiler or furnace covered by Subpart MM
  • Temporary boilers or residential boilers

If your unit IS subject to the Boiler MACT rules, what do you need to know?

Here are some of the highlights and important dates that impact your compliance status:

1/31/16 - Initial Tune-up and Energy Assessment were due.  Also, your Continuous Monitoring System (CMS) and Data Acquisition System (DAS) have to be in operation and startup/shutdown procedures have to be in place.

7/29/2016 - demonstrate compliance with emission limits.

9/30/2016 - or within 60 days following completion of all performance tests/ compliance demonstration your Initial Notification of Compliance Status must be submitted.

Boiler MACT Emission Limits and Work Practice Requirements are dependent on several factors:

  • Whether your major source unit is new or existing
  • Large (>10 MMBtu/hr) or small (<10 MMBtu/hr)
  • The type of fuel burned
  • The boiler design

Existing and new small boilers (<10 MMBtu/hr) and existing and new limited-use boilers are NOT subject to Boiler MACT emissions limits.  If your boiler is subject to emission limits, the boiler design and type of fuel burned will determine the subcategory of your unit, and that subcategory defines what emission limits you must meet.

Boiler MACT Rules FAQ

EPA has provided a list of Frequently Asked Questions related to the Boiler MACT rules. Included below are the general FAQs, as well as FAQs related to the Boiler MACT applicability. A full listing of the FAQs can be accessed at the following web link: https://www.epa.gov/sites/production/files/2016-09/documents/boilermactqanda.pdf.


Q1. Can a boiler that combusts both gas and oil average its emissions when firing gas with those when firing oil?
As stated in 63.7522, emission averaging is only allowed between units in the same subcategory. Averaging emissions of a dual fuel unit burning oil with the emissions of the same unit when burning gas is not permitted. Under 63.7520(c), the unit’s compliance would be based on the emissions when firing oil.

Q2. Can a facility that is currently a major source of HAP become an area source before the first substantive date of the Major Source Boiler MACT (i.e., 2016), and comply with the Area Source Boiler MACT/GACT (NESHAP JJJJJJ) provisions? The EPA's memorandum that was published in 1995 specifically noted the first substantive compliance date of a MACT rule as the last day to switch to an area source, before Once In, Always In takes effect. Does this memorandum still represents EPA's policy?
The “Once In Always In” Policy does represent the Agency’s policy. You are correct that a source must reduce their emissions below major source thresholds prior to the compliance date of the rule.

Q3. Can a facility that is a major source boiler become an area source boiler? If so, what is the latest date by which it may do so, and what has to happen by then?
A facility would need to become an area source before the first applicable compliance date, which would be January 31, 2016 for existing sources. The facility would need to show that their potential to emit HAP is less than 10/25 TPY, and a federally enforceable permit restriction would be one way to show emissions are below major source levels.

Aggregate BoilersQ4. Can a facility that provided an initial notification as a major source later become an area source?
Yes, an existing facility has until January 31, 2016 to become an area source. However, the first applicable compliance date for new sources is January 31, 2013, or the date of startup, whichever is later.

Q5. For a new gas fired boiler installed in 2011, when do the tune-up and energy assessment need to be completed?
The amendments to the major source boiler rule published on January 31, 2013, establish the compliance dates for the tune-up and energy assessment. However, new units are not subject to the requirement to conduct an energy assessment, as indicated in item 4 of Table 3 in the January 31, 2013 amended rule. As for the initial tune-up requirement for new units, the January 31, 2013 amendments establish the date for the initial tune-up for new units. Section 63.7510 was revised and paragraph 63.7510(g) states:

(g) For new or reconstructed affected sources (as defined in § 63.7490), you must demonstrate initial compliance with the applicable work practice standards in Table 3 to this subpart within the applicable annual, biennial, or 5-year schedule as specified in § 63.7540(a) following the initial compliance date specified in § 63.7495(a). Thereafter, you are required to complete the applicable annual, biennial, or 5-year tune-up as specified in § 63.7540(a). This means a new gas-fired unit would need to conduct the initial tune-up by either January 31, 2014 (if required to conduct tune-up annually), January 31, 2015 (if required to conduct tune-up biennially), or January 31, 2018 (if required to conduct tune-up every 5 years).

Q6. Can the 48-hour limitation on use of alternative fuels in the definition of "units designed to burn gas 1” in §63.7575 be interpreted to mean 48 hours of fuel use capacity?
No, the 48 hours of testing allowed for periodic testing of liquid fuel, maintenance, oroperator training under the definition of “units designed to burn gas 1 subcategory” in63.7575 refers to operating hours not fuel capacity or amount of fuel burned. Therefore,a unit that burns liquid fuel for more than 48 hours during any calendar year, notincluding periods of gas curtailment, would be in the “units designed to burn liquidsubcategory.”

Q7. Is there a link to a website that gives guidance on conducting energy assessments?
Here is the link to the DOE website on energy assessment: http://www1.eere.energy.gov/manufacturing/tech_deployment/energy_assessment.html

Q8. If a boiler is planned to be shutdown permanently/decommissioned before the compliance date of the rule, what are the requirements under the rule and would these boilers need to be included in the initial notification due May 31, 2013?
The unit must have an initial notification if it is in operation at the time of the deadline for notification. If the unit was decommissioned prior to the notification date, and is not intended to be restarted, it does not require an initial notification. An existing unit would need to demonstrate compliance by January 31, 2016, but if the unit is decommissioned prior to the compliance date, it would no longer be subject to any rule requirements. EPA recommends that the facility notify the state or EPA Region where the facility is located that the unit has been decommissioned and explain the steps that have been taken to render the unit inoperable, to ensure the unit will not be subject to future inspections. The facility should also contact the state in which they are located to ensure they comply with any state requirements for decommissioning and make sure the unit is removed from the state list of emission sources and any permits are closed out properly.


Q9. Is a small hot water boiler (<1.6MMBtu/hr) subject to the major source boiler rule?
The definition of hot water heater in 63.7575 includes any water heater (not generating steam) that is no more than 120 U.S. gallons in capacity or has a heat input capacity of less than 1.6 MMBtu/hr. Those two thresholds are independent of each other, although both may apply in some cases.

Q10. Is a boiler that was constructed prior to 6/4/2010 but was not in use for several years and started operating again in June of 2012, considered a new source or an existing source?
If nothing has been done to the boiler that qualifies as reconstruction, then it would be an existing unit, based on the original date of construction.

Q11. Is a natural gas-fired boiler that burns oil for LESS than 48 hours during a calendar year considered to be in the “unit designed to burn liquid fuel” subcategory if any of that operation isn’t for “periodic testing” as described in the definition of the “gas 1” term?
Yes. Under the definition of “Unit designed to burn gas 1 subcategory” in §63.7575, the 48 hours allowed in a calendar year, outside of periods of gas curtailment, is only for periodic testing of liquid fuel, maintenance, or operator training.

offshore oilQ12. Does the Major Source Boiler Rule apply to offshore oil and gas operations?
The Major Source Boiler Rule applies to a boiler located at an offshore oil and gas facility if the boiler at the facility meets the definition of an affected source in the rule (see section 63.7485).

Q13. In the process heater definition, does the phrase "an enclosed device using controlled flame" mean all parts of the device are enclosed (the flame side and the other process material) or just the flame part?
The process heater definition phrase "an enclosed device using controlled flame" means just the flame part that is the fuel combustion chamber.

Q14. Does the exemption for “residential boilers” include dorms at universities having more than 4 families?
The Boiler MACT generally does cover boilers located in dormitories located on campuses. The inclusion of the “residential boilers” to the list of boilers not subject to the boiler rules applies to boilers in single family homes located at industrial, commercial (e.g., farms), or institutional (e.g., universities, military bases) facilities. For example, the boiler in the Dean’s residence at a university is a residential boiler, rather than an institutional boiler, even though the residence is owned by the University. So, a boiler located in a dormitory that does not meet the definition of “residential boiler” would be subject to the Boiler MACT.

Q15. Under Boiler MACT, how would a secondary material be classified that received a non-solid waste determination under the NHSM rule?
Under the boilers rules, units are be classified based on the subcategory definitions. That is, if a unit is combusting a material that meets the definition of “biomass or bio-based solid fuel” under the boiler rules it would be considered to be a unit burning that fuel.  The boiler rules also require the source to document that no secondary materials that are solid waste are combusted and, if they burn non-solid waste secondary material, to document why the material was determined not to be a solid waste.

Q16. Are there any waste heat boilers/heat recovery units or duct burners subject to the Boiler MACT?
The Boiler MACT covers boilers as defined in the rule. The amended definition of “Boiler” states waste heat boilers are excluded from this definition. The definition of “Waste heat boiler” was also amended. So, a waste heat boiler, as defined, with or without duct burners is not subject to the Boiler MACT.

Q17. Is a unit combusting coke oven gas considered a Gas 1 unit for purposes of the boiler MACT?
A unit combusting coke oven gas can qualify if as a Gas 1 unit if the coke oven gas meets the Hg level criteria. Also, units combusting process gases that are regulated under another subpart of Part 63 or under certain other regulations are exempt from the definition of "gaseous fuel."

Hot water heaterQ18. Does the regulation define and exclude hot water heaters?
Yes. A hot water heater with a capacity of 120 gallons or less or a hot water boiler (e.g. not generating steam) with heat input capacity of less than 1.6 MMBtu/hr burning oil, biomass, or gas, is not covered under the rule under the definition of hot water heater.

Q19. Is a boiler used for comfort heat located at an industrial facility covered under the rule if it meets the definition of a “hot water heater”?
No. If a unit meets the definition of a hot water heater, it is not subject to the requirements of the rule.

Q20. If a source has a contract with a gas supplier, and the under the terms of the contract the gas supply is curtailed, does this qualify as a period of natural gas curtailment?
Yes. A period of natural gas curtailment or supply interruption means a period of time during which the supply of natural gas is halted for reasons beyond the control of the facility. The act of entering into a contractual agreement does not constitute a reason that is under the control of the facility. However, an increase in the cost of fuel does not qualify as a period of natural gas curtailment. Onsite gaseous fuel system emergencies or equipment failures may qualify as periods of supply interruption if the emergency or failure is beyond the control of the facility.

Q21. Is there a limit on the number of hours a gas-fired boiler may burn oil during periods of natural gas curtailment or supply emergencies and still be gas-fired?
No. The 48-hour annual limit in the definition of “unit designed to burn gas 1” subcategory applies to combustion of liquid fuel for the purpose of testing of liquid fuel, maintenance, or operator training.

Questions or Need Help?

Give us a call at (512) 301-1451 and we’ll be happy to assist in answering your questions.

Additional Useful Links and Guidance

EPA Area source boiler webpage - www.epa.gov/boilercompliance

Combustion Portal - http://www.envcap.org/boiler/

EPA combustion webpage - www.epa.gov/airquality/combustion/actions.html

EPA boiler webpage - www.epa.gov/ttn/atw/boiler/boilerpg.html

Contact us