Carbon monoxide safety first. Converting a boiler to gas changes what goes up the chimney — and what the chimney was built to handle. A flue sized for oil may be wrong for gas; a cracked liner that survived oil soot can fail under gas condensation. If your chimney isn’t verified before the conversion, the first sign of trouble can be a CO alarm — or worse. Inspect the chimney before the gas gets turned on, not after.
Call (347) 297-9646 or WhatsApp us — 24/7. Level 2 camera inspection with an affidavit-ready report for oil-to-gas conversions.
Why the chimney inspection is the make-or-break step of a conversion
Every year, NYC building owners convert boilers from oil to natural gas — DOB NOW records show 91 job filings mentioning oil-to-gas boiler conversion since January 2025 alone. Most of the planning goes into the boiler, the burner, and the gas meter. The chimney is the part that gets assumed. That’s the mistake.
Oil and gas do not vent the same way. Oil exhaust is hot and dirty; gas exhaust is cooler and wet — loaded with water vapor. An oversized masonry flue that handled oil for decades can condense gallons of acidic moisture a day under gas, eating the liner from the inside. A cracked clay tile that oil soot masked can leak carbon monoxide straight into the chase once the draft profile changes. And the NYC DOB already flags this: for a lawfully existing boiler replacement in a 1–5 family building, licensed plumbers must file the OP128 form with a chimney affidavit confirming the chimney is in good working order. The gas utility’s own process requires signed affidavits before larger replacement meters go in for oil-to-gas conversions. Without a documented chimney inspection, the conversion stalls at the paperwork — or proceeds on a chimney nobody verified.
Across the city, DOB records carry 869 chimney violations — 490 of them still open and active — and New Yorkers filed 401 chimney-related 311 complaints so far in 2026. Old oil chimneys are overrepresented in both. If your chimney predates the conversion, assume it was never checked for gas.
What our conversion inspection actually covers
This is a Level 2 camera inspection, built specifically for fuel conversions. A camera runs the full flue, top to bottom, and you get evidence — not an opinion.
Full flue interior scan.
Every foot of the flue on camera: clay tile condition, liner joints, soot and scale depth, blockages, offsets, fallen tile fragments. You see exactly what the new gas exhaust will travel through.
Flue sizing vs. the new boiler.
The most common conversion failure. We measure the flue and check it against the new boiler’s venting requirements under the NYC Fuel Gas Code venting tables. Oversized flue under gas = chronic condensation and draft failure. Undersized = spillage. If the sizing is wrong, we tell you before the boiler is ordered.
Condensation and corrosion mapping.
Gas exhaust condenses in flues built for oil. We document existing corrosion and acidic damage so you know whether the liner survives the conversion or needs replacement first.
Draft and spillage test.
We verify the boiler drafts correctly through the existing chimney and check for exhaust spilling at the draft hood — the test a gas company inspector would want to see passed.
Smoke test on request.
Pressurizing the flue with smoke reveals leak paths that even a camera can miss — cracked tiles, failed joints, gaps into wall cavities. For conversions, we recommend it.
The affidavit-ready written report.
You get photos and a written report documenting flue condition, sizing, and suitability for gas venting — the document your plumber needs for the OP128 chimney affidavit filing, and the evidence your gas company wants before it signs off. Reports are delivered in days, not weeks.
What happens when the chimney fails the conversion check
Three honest outcomes, and we recommend only what the camera shows:
The chimney is ready.
Liner intact, sizing correct, draft strong. Your plumber gets the affidavit-ready report and the conversion moves forward. This is the best money you’ll spend on the project.
The chimney needs a stainless-steel liner.
Cracked tiles, corrosion, or wrong sizing — we install a new stainless-steel liner sized to the new gas boiler under the Fuel Gas Code venting tables. Brooklyn starts at $3,000, Manhattan starts at $5,000, labor and materials included. The liner we install is the flue your conversion deserves.
The chimney needs repair first.
Deteriorated crown, failed flashing, damaged smoke chamber, or masonry damage. Basic chimney repairs start at $500. We fix what’s broken, re-inspect, and then sign off.
The pre-conversion timeline: when to call us
Call before the boiler is ordered — not the week before the gas turn-on. The right sequence: (1) chimney camera inspection and sizing check, (2) liner or repair work if needed, (3) boiler and burner installation by your licensed plumber, (4) affidavit-ready report delivered to the plumber for DOB filing, (5) gas company sign-off. Discovering a wrong-sized flue after the new boiler is sitting in the basement turns a planned conversion into a mid-winter emergency — and 91 conversion filings since January 2025 means scheduling pressure is real.
A Level 2 camera inspection for oil-to-gas conversion: Brooklyn starts at $199, Manhattan starts at $399 — roof, liner interior, draft test, photos, and affidavit-ready written report included.
Frequently asked questions: oil-to-gas conversion chimney inspection
Does the gas company require a chimney inspection before converting?
The conversion paperwork requires proof the chimney is sound. NYC DOB requires a chimney affidavit — a signed statement that the chimney is in good working order — when a lawfully existing boiler, furnace, or water heater is replaced in a 1–5 family building. Gas utilities require their own affidavits before installing larger replacement meters for oil-to-gas conversions. Our camera inspection and written report give your plumber the documented evidence behind those affidavits.
Can my existing oil chimney handle a gas boiler?
Sometimes — but it has to be verified, not assumed. The flue must be the right size for the new boiler’s venting tables, the liner must be intact enough to survive gas condensation, and draft must be proven. In older NYC buildings, the flue was sized decades ago for a different boiler on a different fuel. Our inspection measures, documents, and answers that question with evidence.
What does a smoke test show that a camera doesn’t?
A camera shows the flue’s interior surface; a smoke test shows whether the flue actually holds exhaust. Pressurizing the flue with smoke reveals leaks through cracked tiles, failed joints, and gaps into wall cavities that a camera can pass over. For fuel conversions we recommend both — the camera finds damage, the smoke test proves containment.
How far ahead of the conversion should I book the inspection?
Book the chimney inspection before you order the boiler. If the flue sizing is wrong or the liner is shot, that changes the project scope — discovering it early saves you from re-ordering equipment or opening walls twice. Heating season is here — slots fill fast, book before the rush.
Do you work with our plumber or boiler contractor?
Yes. We do the chimney side — inspection, report, liner, repairs — and hand your licensed plumber the affidavit-ready documentation they need for the DOB OP128 filing and the gas company. One project, two specialists, no finger-pointing.
CTA. Oil-to-gas conversion on the calendar? Don’t let the chimney be the part nobody checked. Call (347) 297-9646 or WhatsApp us for a Level 2 camera inspection with an affidavit-ready report — 24/7 emergency chimney service across Brooklyn and Manhattan.