Carbon monoxide safety first. A chimney affidavit is a signed, sworn statement that a chimney has been inspected and is in good working order — the piece of paper that keeps a bad flue from being connected to a new gas burner. In New York City, it stands between your boiler project and a conversion that vents exhaust into your building through a cracked liner. Know what it is before your plumber asks for it.
The one-paragraph definition
A chimney affidavit is a signed certification — made by a qualified professional after a chimney inspection — stating that the chimney serving a boiler, furnace, or water heater has been examined and found sound and suitable for its intended use. It is not the inspection itself; it is the documented outcome of the inspection. It carries a signature, a date, and the findings that support it: flue condition, liner integrity, and confirmation the chimney can safely vent the appliance connected to it.
Call (347) 297-9646 or WhatsApp us — 24/7. Need a chimney affidavit for a boiler replacement or oil-to-gas conversion? Our Level 2 camera inspection produces the affidavit-ready report your plumber and gas company require.
Where NYC actually requires one
Two places in the NYC process, and they are not the same affidavit:
1. DOB boiler-replacement filings — the OP128 chimney affidavit. When a licensed plumber files for a lawfully existing boiler, furnace, or water heater replacement in a 1–5 family building, NYC DOB requires the OP128 form to include a chimney affidavit: a signed statement confirming the chimney is in good working order. The plumber cannot complete the filing without it. The affidavit is only as good as the inspection behind it — DOB Appendix-A’s own boiler inspection checklist has a CHIMNEY & VENTS section, so a plumber who signs a chimney affidavit based on a guess is staking their license on an assumption.
2. Gas utility meter applications — the oil-to-gas affidavit. For oil-to-gas conversions that need a larger replacement gas meter, the gas company’s own process requires signed affidavits confirming the chimney condition. This is the utility protecting itself — and you — before it turns gas into a building through a flue nobody verified.
Both require the same thing upstream: a documented, evidence-backed chimney inspection. Photos. A written report. Findings a third party can rely on.
What a proper chimney affidavit is based on
An affidavit is only credible if it rests on an inspection that would convince a stranger. For boiler flues and conversions, that means a Level 2 camera inspection:
- Full flue interior on camera — liner condition, tile cracks, joint integrity, soot and scale depth, blockages, fallen debris. The affidavit must describe what was found, not just declare the chimney “fine.”
- Flue sizing vs. the appliance — the flue must be correctly sized for the boiler or burner it serves, checked against the NYC Fuel Gas Code venting tables. This is the conversion-killer finding: an oversized oil-era flue that will condense acid under gas.
- Draft and spillage verification — proof the appliance actually drafts through the chimney, not spilling exhaust at the draft hood.
- A written report with photos — the deliverable. The plumber files against it; the gas company relies on it; the building keeps it in its file.
A Level 2 camera inspection with an affidavit-ready written report: Brooklyn starts at $199, Manhattan starts at $399 — roof, liner interior, draft test, photos, and the report included.
What it does NOT include (common confusion)
- It is not a DOB permit. The affidavit supports the plumber’s filing; the filing is the permit application.
- It is not the annual boiler inspection report. Annual inspection reports are a separate requirement (H-stamped and E-stamped low-pressure boilers in 6+ family residential, commercial, and mixed-use buildings), filed to DOB within 14 calendar days. The chimney affidavit belongs to the boiler installation/replacement paperwork, not the annual cycle.
- It is not a repair. If the inspection finds a cracked liner, wrong sizing, or a failed crown, the affidavit can’t be honestly signed until the work is done. A new stainless-steel liner (Brooklyn starts at $3,000, Manhattan starts at $5,000, labor and materials included) or basic chimney repairs (start at $500) come first; the affidavit follows the correction.
- It is not free to fake. NYC carries 869 DOB chimney violations mentioning “chimney” — 490 still open and active, and New Yorkers filed 401 chimney-related 311 complaints in 2026. A signed affidavit attached to a failing chimney is a liability with a paper trail.
The timeline: when to get one
Start the chimney inspection before the boiler is ordered or the gas application goes in. The sequence: (1) Level 2 camera inspection and sizing check, (2) liner or repairs if the camera says so, (3) affidavit-ready report to your licensed plumber, (4) plumber files OP128 with the chimney affidavit, (5) gas company receives its affidavits and approves the meter. Heating season is here — a conversion inspection booked today keeps the paperwork off the critical path.
Frequently asked questions: chimney affidavits in NYC
Who signs the chimney affidavit — me, my plumber, or the chimney company?
The affidavit is a signed professional statement about chimney condition. Your plumber files it as part of the OP128 boiler-replacement filing; the chimney company provides the inspected, documented evidence behind it (camera findings, photos, written report). The plumber signs the filing based on documented inspection evidence — not a phone call.
Can a chimney affidavit be based on a visual-only (Level 1) inspection?
For a boiler replacement or oil-to-gas conversion, no responsible professional should. A Level 1 inspection can’t see inside the flue — no liner interior, no sizing verification, no condensation mapping. Conversions and boiler replacements need Level 2 camera evidence: that’s what makes the affidavit defensible if the gas company or DOB ever asks questions.
How long does it take to get a chimney affidavit?
The inspection itself takes a few hours on site. The affidavit-ready written report follows in days, not weeks. The real schedule risk is what the camera finds: if the flue needs a liner or repairs, that work — and the correction documentation — comes before an honest affidavit can be signed.
What if my chimney fails the inspection behind the affidavit?
Three outcomes: it’s ready (plumber gets the report and files), it needs a stainless-steel liner sized to the appliance, or it needs repairs first (crown, smoke chamber, masonry). Basic chimney repairs start at $500. We fix what’s broken, re-inspect, document the correction — and then the affidavit can be signed on a clean record.
Is the chimney affidavit the same document the gas company asks for?
Related but separate. DOB’s OP128 chimney affidavit covers the boiler-replacement filing in 1–5 family buildings; the gas utility requires its own affidavits before installing larger replacement meters for oil-to-gas conversions. Both require the same upstream evidence: a camera inspection with a written, photographed report. One inspection feeds both documents.
My boiler is being replaced but I’m staying on oil. Do I still need one?
If your licensed plumber is filing a lawful boiler replacement in a 1–5 family building, the OP128 chimney affidavit requirement applies to the replacement regardless of fuel. Any new boiler on an old flue deserves a camera inspection first — the affidavit is just the paperwork catching up to that fact.
CTA. Boiler replacement or oil-to-gas conversion in the works? Get the chimney camera-inspected and documented before the paperwork stalls. Call (347) 297-9646 or WhatsApp us — 24/7 emergency chimney service across Brooklyn and Manhattan.