Summary: The National Fire Protection Association® (NFPA®) publishes the NFPA 85 as a standard for Boiler and Combustion Systems Hazard Code. Changes to the code happen frequently and do not always align with the current or soon to be released edition. A plant that treats code compliance as a five-year checkbox can miss a change that took effect years before the next edition arrives. Thermal Economy provides support to close possible compliance gaps.
Key Takeaways:
- A Tentative Interim Amendment (TIA), revised NFPA 85's manifolded vent line sizing rule in September 2025, months before most plants would think to check for a mid-cycle change.
- The 2027 edition is currently moving through committee. It is possible changes to this new edition could be published as TIAs before the publication date.
- A control system built around fixed setpoints from an old edition cannot flag a mid-cycle amendment on its own. Catching a change like this depends on paying close attention to the TIA's published by the NFPA.
The NFPA 85 is being revised continuously.
Most plant engineers think about code compliance the way they think about a calendar. A new edition of the NFPA 85 comes out every few years, someone reviews the changes, and the plant updates whatever needs updating. This cadence misses a category of change that happens quietly, between editions, that can have a measured effect on compliance and safety.
The National Fire Protection Association® (NFPA®) calls these in-between edition changes a Tentative Interim Amendment, or TIA. A TIA revises a specific section of a current edition without waiting for the full revision cycle to finish. A TIA goes through the same technical committee review as any other code change. Once the Standards Council issues the amendment, the change takes effect on the date the NFPA sets. This date usually predates an edition publication and may go months without being published in the most current NFPA 85. The next section will outline a recent TIA that took effect in 2025, that has yet to be published in a current NFPA 85.
TIA 23-1, a change in the vent-sizing rule.
TIA 23-1 was issued by the NFPA Standards Council on August 20, 2025, with an effective date of September 9, 2025. TIA 23-1 revises paragraphs 4.9.4 and 4.9.4.1 of the 2023 edition, the current edition of NFPA 85 in effect for most plants today.
The change governs manifolded vent lines, the shared vent piping that serves multiple burner valves in a system. Before the amendment, the rule stated the manifold line's cross-sectional area could not be smaller than the largest single vent line feeding into it. TIA 23-1 tightens this rule. Now, the manifold line's cross-sectional area has to meet the greater of two calculations:
1. The largest vent line plus 50 percent of the combined area of the remaining vent lines
2. Or, the sum of the two largest vent lines.
The same standard applies where a vent line is sized using the leak detection limit of the valve-proving system under 4.9.2.1.
In plain terms, a manifold that passed under the 2023 edition wording might undersize the shared vent path once you run both calculations required by the 2025 amendment. The tightened calculation changes what a correctly sized system looks like on a boiler running today.
A vent-sizing rule sounds like the kind of detail only a code committee could care about. On a system with multiple burners sharing a vent manifold, undersized vent piping can slow the pressure relief the vent path is there to provide during a valve-proving test or a purge sequence.
This is an example of why TIAs are necessary. A technical committee does not wait three years to fix a sizing formula it has identified as insufficient. By design, the committee process, and the interim mechanism, move faster than the printed edition does, precisely because some corrections cannot wait for the next cycle.
The NFPA 85, 2027 edition.
Separate from TIA 23-1, the next full edition of the NFPA 85 is set to publish in 2027. The first draft public comment window closed on January 6, 2026. The committee has since moved on to a second draft ballot, another step closer to a printed edition.
None of this changes what applies to your plant today. The 2023 edition, as amended by TIA 23-1, is still the operative code. But a committee actively drafting the next edition is a signal worth tracking. Changes proposed in a first draft sometimes surface as a TIA before the edition containing them is printed, much like TIA 23-1. Our team at Thermal Economy stays abreast of amendments and draft updates as they are published.
How to stay ahead of a mid-cycle change.
A burner management system does not know when a code section changes. The system runs the sequence it was commissioned to run, checks the permissives it was built to check, and reports exactly what it was told to report. If a vent-sizing calculation was correct under the old rule and is now insufficient under TIA 23-1, the control system has no way to flag this gap on its own. Someone has to know the rule changed, and then go check the equipment against it.
The time between NFPA 85 editions is a documentation and awareness problem more than an equipment problem. A person is needed to track changes in code in real time. A control system with drawings and specifications available at the HMI (Human-Machine Interface) makes that check faster once someone knows to run it. Your plants vent, valve, and permissive sizing information need to stay current and accessible, so a revised calculation can be checked against your system in minutes.
Catching a change like TIA 23-1 before an inspector does starts with checking NFPA's TIA list for the codes your equipment falls under on a regular schedule, not just when a new edition ships. TIAs post to nfpa.org as they are issued, with the effective date.
Someone to keep tabs.
The committee at NFPA is actively drafting the next edition, pointing to new areas of scrutiny. Thermal Economy makes sure this information is applied in compliance with effective dates.
It might be time to have us perform an onsite audit where you'll get a comparison against all current requirements. This same review can cover the rest of your burner management system against NFPA 85 as well.
There is no need to play a constant game of catch-up. Let our team of technicians help keep your system up to the latest standards.
Frequently Asked Questions (FAQ)
What is NFPA 85?
NFPA 85, the Boiler and Combustion Systems Hazards Code, is the National Fire Protection Association standard governing the design, installation, and operation of burner management and combustion control systems for fired boilers, heaters, and related equipment. NFPA 85 sets requirements for safety interlocks, purge sequences, flame monitoring, and related safeguards. The 2023 edition is the current edition.
What is a Tentative Interim Amendment (TIA), and how is it different from a new edition?
A Tentative Interim Amendment, or TIA, revises a specific section of the current edition of a code without waiting for the full revision cycle to complete. A TIA goes through committee and Standards Council review, then takes effect on a set date. A new edition replaces the entire document on a multi-year cycle; a TIA changes one requirement in between editions.
Does TIA 23-1 apply to a boiler commissioned under an older edition of NFPA 85?
TIA 23-1 amends the 2023 edition specifically. Whether it applies to an older installation depends on which edition your jurisdiction or insurer requires you to follow and whether your authority having jurisdiction has adopted the 2023 edition with this amendment. Confirm the applicable edition with your local authority having jurisdiction before assuming a status either way.
How do I know if my facility's manifolded vent line sizing meets the current requirement?
Compare your manifold line's cross-sectional area against both calculations TIA 23-1 requires, the largest vent line plus 50 percent of the remaining vent lines' combined area, and the sum of the two largest vent lines. The manifold must meet whichever of the two produces the larger required area.
Does complying with a TIA require replacing hardware, or just re-verifying a calculation?
The calculation result determines the answer. Many systems that were sized conservatively already meet the revised requirement without any physical change. A system sized close to the old minimum may need a larger manifold line or a documented engineering justification.
What happens if an inspector cites a TIA my plant hasn't implemented yet?
An inspector citing an issued and effective TIA is citing a change already part of the applicable code, not a proposed future one. Verify your system against the amended requirement and document the result, whether that means the system already complies or needs a correction. If there's a genuine question about how the amendment applies to your equipment, raise it with your authority having jurisdiction or a code consultant.
Why does it matter who is tracking code changes for my burner management system (BMS)?
A control system reports what it was built to report. The system does not monitor NFPA's amendment activity on its own. A plant that relies solely on the next scheduled code review can miss a TIA that has already been in effect for months. The person or provider responsible for your BMS should be watching code development between editions, not only reviewing it when a new edition ships.
