Vented or Vent-Free — Your Building's Code Tells You Which

In most cases, no — and that’s the most common surprise homeowners run into when they buy a set before calling for installation. A vent-free gas log set is designed to burn with the damper closed, exhausting combustion byproducts directly into the room. Many NYC residential buildings — particularly co-ops and buildings with tight envelope construction — prohibit these sets outright due to indoor air quality and carbon monoxide concerns. For most NYC masonry fireplaces, a vented gas log set is the right answer: it requires an open damper and a functioning flue, and it’s compatible with the existing wood-burning flue infrastructure in brownstones, row houses, and most co-op units. We confirm what your specific building permits before any product is recommended.

Because the work falls under two different trades in New York City. Prime Chimney — the chimney company — installs and configures the log set itself, the burner assembly, the damper clamp where required, and confirms the flue is in serviceable condition. The gas line connection to the firebox appliance is a separate scope. Under NYC plumbing code, any new gas line branch or connection must be performed by a licensed master plumber. That isn’t a quirk of how we work — it’s how the trade boundary is defined in NYC. We coordinate the handoff with the plumber so the chimney-company scope and the plumber scope are defined clearly before work begins so there are no gaps between the two trades.

Often yes — that’s the most common gas log installation we handle, particularly in Brooklyn brownstones and Queens row houses with original wood-burning masonry flues. The conversion uses a vented gas log set installed in the existing firebox, with combustion gases exhausting through the existing flue. The flue itself has to be in serviceable condition: the damper has to open fully and hold position, the liner has to be intact, and the flue opening area above the firebox has to be adequate for the burner output. If the damper is stuck or the liner has deterioration, those issues get addressed before the log set goes in — but for most pre-war NYC masonry fireplaces in working condition, the conversion is straightforward.

For a standard conversion where the existing flue is in serviceable condition, the timeline is typically two visits — the assessment visit to confirm code, measure the firebox, and check the damper and flue, then the installation visit once the permitted log set is selected. Between those, the homeowner orders the appropriate set based on the BTU sizing we recommend, and the licensed master plumber is scheduled to run the gas line connection. For conversions where the damper or flue needs work first, add one or two additional visits to address those repairs before the installation itself. We map the full timeline at the assessment visit so you know what to expect before any product is purchased.

BTU sizing matches burner heat output to the firebox dimensions and room volume. The principle is straightforward: an oversized burner in a small firebox produces incomplete combustion — meaning the burner can’t draw enough air to burn the gas cleanly — and that elevates carbon monoxide output. An undersized burner produces a small flame that doesn’t look right and doesn’t generate the heat the homeowner expected. The sizing step matches BTU output to the actual firebox dimensions we measure during the assessment visit. The product selection follows that number — not the other way around. Call (347) 801-0260 to schedule your firebox assessment.