Ventless Gas Stoves: How Vent-Free Works, Where It's Legal, and Which to Buy
No Sales Tax in any state on both vent-free gas stoves we carry. A ventless gas stove (also sold as a vent-free gas stove) burns natural gas or propane with no chimney, flue or vent pipe, so nearly all of its heat stays in the room, and it keeps running when the power goes out. The trade-off is that everything the flame produces stays in the room too. This guide covers how they work, where they're legal, how big a room one needs, and what to check before you order.
Quick answer: which vent-free gas stove to buy
- Want the blower included, or want it to sit inside an old masonry fireplace: the Buck Stove Model T-33 ($1,815). Order T-33NG for natural gas or T-33LP for propane.
- Want a traditional freestanding stove look: the Buck Stove Townsend II (from $1,899, blower optional). Order TS2NG or TS2LP.
- Before either: confirm vent-free is allowed where you live, and that the room has at least 1,600 cubic feet of open space (about 200 sq ft with 8 ft ceilings).
Both are made in the USA by New Buck Corporation, rated 22,400–32,000 Btu/h, and ship with No Sales Tax.
How a ventless gas stove works
A vented gas stove sends its exhaust outdoors through a pipe. A vent-free stove has no pipe at all: its burner is tuned to burn cleanly enough that the combustion products can be released into the room. That's why the heat output is so close to the gas input. ComfortBilt rates both Buck stoves at 99.9% efficiency, because there's no flue for heat to escape through.
Three parts do the work:
- Oxygen depletion sensor (ODS). The pilot assembly doubles as a safety shutoff. Both Buck manuals say the ODS pilot shuts the heater off if there is not enough fresh air in the room. It reacts to low oxygen. It is not a carbon monoxide detector, so you still want a CO alarm in the room.
- Standing pilot. A small pilot flame stays lit when the burner is turned off, ready to relight the main burner when the thermostat calls for heat.
- Piezo igniter. You light the pilot with a push-button spark. The T-33 manual says the system "requires no matches, batteries, or other sources to light." With no electrical parts needed to make heat, the stove keeps working in an outage. Only the blower needs an outlet.
Both stoves also take an optional remote or wall thermostat, which cycles the burner on and off to hold the temperature you set.
Where vent-free gas stoves are legal
This is the first thing to check, because the answer depends on your state and town, not on the stove. Both Buck manuals say plainly that state and local codes in some areas prohibit vent-free heaters. The rules we've confirmed from the source:
- California: Title 25, §34 of the California Code of Regulations says no unvented fuel-burning heaters shall be permitted in any dwelling unit or guest room offered for rent or lease. Treat California as a no, and confirm with your building department before buying anything.
- Minnesota: the state fuel gas code, Minn. R. 1346.5621, replaces the model code section with a flat rule: unvented room heaters and unvented decorative appliances shall not be installed in any dwelling or occupancy.
- Local permits: some places allow them only with paperwork. In Massachusetts, the City of Worcester's unvented heater application requires a fire department permit, a carbon monoxide detector in the room with the heater, and a final inspection by fire and gas inspectors.
- The model code most states use: the International Fuel Gas Code, Section 621, says unvented room heaters can't be the sole source of comfort heating in a dwelling (621.2) and can't be rated above 40,000 Btu/h (621.3). Both Buck stoves top out at 32,000 Btu/h, and both manuals call them supplemental heat.
The manufacturer adds its own limits on top of the code, in both manuals:
- Never in a bedroom or bathroom.
- Never in a recreational vehicle.
- A permanently located manufactured home is allowed where state or local codes don't prohibit it.
- Above 4,500 feet elevation, the pilot may go out.
If you're in a ban area, a mountain town, or you need a bedroom heater, skip vent-free and look at the alternatives further down.
How big a room a vent-free stove needs
Both manuals use the same worksheet: divide the room's volume by 50 cubic feet to get the most Btu/h that space can support. Size it on the stove's maximum rating. At 32,000 Btu/h, that's 1,600 cubic feet. A room smaller than that counts as unusually tight construction, and the stove shouldn't go there unless extra combustion and ventilation air is provided, as the manual describes.
| Ceiling height | Minimum floor area at 32,000 Btu/h |
|---|---|
| 8 ft | 200 sq ft |
| 9 ft | 178 sq ft |
| 10 ft | 160 sq ft |
| 12 ft (vaulted) | 134 sq ft |
That's a floor, not a target. A bigger, more open space dilutes moisture and combustion byproducts better, so a living room open to a kitchen is a far better spot than a closed-off den that only just passes.
Moisture, odor and ventilation
Burning gas makes water vapor, roughly a gallon for every 100,000 Btu burned. A stove at 32,000 Btu/h for five hours adds about a gallon and a half of water to the room's air. In a dry winter house that can feel pleasant. In a tight, already humid house it shows up as fogged windows and, over time, mildew. Both manuals warn that vent-free heaters add moisture to the air and that a room without enough ventilation air may grow mildew.
Odor is the other common complaint. The manuals list two normal causes:
- A slight smoke or smell during the first burns, as manufacturing residue cooks off. A "paper burning" smell from new logs is also normal.
- Impurities in the room air, such as cleaning products, paint, or cigarette smoke, burning in the flame.
The manuals' fix for condensation and odor is the same: open a window or door to ventilate. If a smell persists after the first few burns, turn the stove off and have a gas technician check it.
Natural gas or propane: order the right one
Each Buck stove is built for one fuel at the factory, and both manuals say it is not convertible for use with other gases. There is no conversion kit, so check your supply before you order:
- Natural gas: a utility line to the house. Order the NG version.
- Propane (LP): a tank. Order the LP version. Propane installs need an external regulator that cuts tank pressure to a maximum of 13" W.C.
Either way, the gas line, shutoff valve and leak test are a job for a qualified gas installer. Running a gas line is often the biggest cost on the job, so get that quote before you budget only for the stove. If you're weighing propane against other fuels on running cost, our pellet stove vs propane comparison works through the cost per million Btu.
Our vent-free picks: Buck Stove T-33 and Townsend II
Buck Stove Model T-33. The T-33 ($1,815) comes with legs and an 85 CFM heat-activated, variable-speed blower. It's the one to pick if you have a drafty masonry fireplace you've stopped using: the manual allows it inside a fireplace with an opening at least 32-1/2" wide, 24" high and 12" deep. Once it's in, you can't burn wood in that fireplace again. The T-33 manual also notes that in a power outage you can use it as your primary heat source, which is the situation most buyers are planning for.
Buck Stove Townsend II. The Townsend II is a steel freestanding stove with a traditional look and a visible log fire. It's $1,899 without a blower, or $2,268 with the MA CVF714 blower kit, the only blower Buck approves for it. It's certified to ANSI Z21.11.2 and isn't meant to go inside a fireplace. Call us to confirm the finish before you order.
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| Buck Stove Model T-33 | Buck Stove Townsend II | |
|---|---|---|
| Input | 22,400–32,000 Btu/h | 22,400–32,000 Btu/h |
| Natural gas SKU | T-33NG | TS2NG, TS2NGB (blower) |
| Propane SKU | T-33LP | TS2LP, TS2LPB (blower) |
| Blower | Included, 85 CFM | Optional |
| Install | On legs, or inside a masonry fireplace | Freestanding |
| Clearances | 4" sides and back, 48" ceiling | 4" sides and back, 48" ceiling |
| Price | $1,815 | $1,899; $2,268 with blower |
Both stoves need a metal or wood panel under them covering their full width and depth, and furniture and curtains kept at least 48" from the front, top and sides. The full manuals are linked under Documents on each product page: T-33 manual and Townsend II manual. You can also compare both on one page in our vent-free gas stoves for sale.
Vent-free vs direct-vent vs wood and pellet
A vent-free stove isn't the only way to heat a room without a masonry chimney. Here's how it stacks up:
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| Vent-free gas | Direct-vent gas | Pellet stove | Wood stove | |
|---|---|---|---|---|
| Venting | None | Coaxial pipe through wall or roof | 3" pipe through a wall | 6" chimney |
| Exhaust goes | Into the room | Outside | Outside | Outside |
| Heats in a power outage | Yes | Some models | No | Yes |
| Room-size minimum | Yes | No | No | No |
| Can be main heat | No | Yes | Yes | Yes |
| Bedroom use | No (Buck manuals) | Per its manual | Per its manual | Per its manual |
| Example we sell | Buck T-33 | Not carried | ComfortBilt HP21 | Drolet Escape 1500 |
Choose vent-free when you need supplemental heat in a large, open room, you want heat through power outages, and it's legal where you live. A direct-vent gas stove keeps the gas convenience and sends exhaust outside, but needs a wall or roof vent. A pellet stove like the ComfortBilt HP21 ($1,949) vents through a 3" wall pipe and can heat a whole floor, but needs electricity. A wood stove like the Drolet Escape 1500 ($1,349) heats without power and can be your main heat, but needs a real chimney. We go deeper on that choice in heat without a chimney: ventless gas vs a pellet stove.
Ventless gas stove FAQ
Are vent-free gas stoves safe?
Used as designed, yes: they're certified to ANSI Z21.11.2, and the ODS pilot shuts the stove off if room oxygen runs low. The risks come from installing one in a room that's too small, a bedroom, or a tight house, and from skipping cleaning. Put a CO alarm in the room, keep the room above the 50 cu ft per 1,000 Btu/h minimum, and run it as supplemental heat. Our vent-free safety guide covers the code and air-quality side in detail.
Can a ventless gas stove be my only heat source?
No, not as a permanent setup. IFGC 621.2 bars unvented room heaters as the sole source of comfort heat in a dwelling, and both manuals say not to install one as your primary heat. The exception the T-33 manual allows is a power outage, when the stove can carry the house until the furnace comes back.
Why does my new vent-free stove smell?
A light smoke or "paper burning" smell during the first few burns is normal, from manufacturing residue and new logs. After that, smells usually come from something in the room air (paint, cleaners, candles, smoke) passing through the flame. Ventilate the room. If an odor persists, turn the stove off and call a gas technician.
Will a vent-free gas stove work at high altitude?
Both Buck manuals warn that running the heater above 4,500 feet could cause pilot outage. If you live above that, a direct-vent appliance or a wood stove is the safer choice.
Can I put one in a mobile home or cabin?
A permanently located manufactured home is allowed by both manuals where state and local codes don't prohibit it. RVs are not. A cabin is fine if the room meets the volume rule and local code allows vent-free. For solid-fuel options in manufactured homes, see our mobile home wood and pellet stove guide.
Do vent-free gas logs work the same way?
Same burner principle and the same ODS, but a log set goes inside a fireplace and is usually bought for the flame. Our ventless vs vented gas logs guide explains the difference.
Related guides
- Are ventless gas fireplaces safe?
- Heat without a chimney: ventless gas vs a pellet stove
- Ventless vs vented gas logs
- Pellet stove vs propane running cost
Questions about fuel, room size or local rules? Call us at 1-888-914-0022. Both Buck Stove vent-free gas stoves ship with No Sales Tax in any state.