Propane Heaters in Ice Shanties and Blinds: Run Time and Safety

How long a tank lasts

A propane heater burns fuel at a steady rate set by its BTU rating. BTU (British thermal unit) is a measure of heat. A 9,000 BTU heater burns 9,000 BTU of propane every hour on that setting, so run time comes down to how much propane you have and which setting you use.

Here's what that works out to for the heaters people ask about most, using about 21,570 BTU per pound of propane and 1 lb per cylinder, the same as our calculator:

Our math: pounds of propane × 21,570 BTU per pound ÷ heater BTU per hour. That's the EIA's 91,452 BTU per gallon divided by 4.24 lb per gallon. A "1 lb" cylinder actually holds 16.4 oz, so you may get a few minutes more. BTU ratings and maker's claims from Mr. Heater's product pages, manuals and Big Buddy spec sheet. *Hunting Buddy run times are a Mr. Heater answer posted on Tractor Supply's product page; Mr. Heater's own page doesn't list them. Real run times are often shorter in the cold, as explained below.

Mr. Heater's own numbers back up the math. Its Portable Buddy page lists a burn rate of 0.099 gallons per hour on high. At the U.S. Energy Information Administration's 91,452 BTU per gallon, that's about 9,050 BTU per hour, right on the 9,000 rating.

Two takeaways for the ice or the stand:

• For a full day on high, bring a bigger tank. An 8-hour day at 9,000 BTU takes 3 or 4 one-pound cylinders, or a small part of a 20 lb tank.
• Run on low whenever you can. Low doubles a Buddy's run time.

Plug in your own heater, setting and tank size in our Propane Heater Run Time Calculator.

Doing the math yourself

You need two numbers: the BTU in your tank and the heater's BTU per hour.

1. Find the pounds of propane. A "1 lb" cylinder holds 16.4 oz, which is 1.025 lb. A "20 lb" grill tank holds up to 20 lb when full.
2. Multiply by about 21,570 BTU per pound. 1 lb × 21,570 = about 21,600 BTU. 20 lb × 21,570 = about 431,000 BTU.
3. Divide by the heater's BTU per hour on the setting you'll use. It's printed on the heater's label and in the manual.

Example: a Hunting Buddy on high (12,000 BTU) with one cylinder: 21,570 ÷ 12,000 = about 1.8 hours. On a 20 lb tank: 431,400 ÷ 12,000 = about 36 hours.

Treat the answer as the best case. The last bit of propane in a cold cylinder often won't come out.

Why the cylinder dies early in the cold

This is one of the most common complaints on ice fishing forums: the Buddy dims and goes out with a quarter of the cylinder still sloshing around.

Here's why. Propane sits in the cylinder as a liquid and boils into gas to feed the heater. It boils at about −44 °F, so it still boils on a cold day, but boiling chills the cylinder. A small cylinder can't pull heat back in from cold air fast enough, so the pressure and the flame drop. The emptier it gets, the worse it gets.

What helps:

• Start with a warm cylinder. Keep spares in the truck cab or an inside coat pocket until you need them.
• Use a 20 lb tank on the ice for long days. A bigger tank has much more metal and liquid to hold heat. Mr. Heater sells a hose and filter to connect the Buddy to a 20 lb cylinder. Use the parts Mr. Heater makes for your model, since its pages warn that unauthorized accessories are prohibited.
• Keep the heater off bare ice. Anglers report a scrap board under it helps.
• Burn up leftovers on a lantern or camp grill outside, instead of throwing away partly full cylinders.

Never warm a cylinder with a flame, a heater or anything hot. If a cylinder is too cold to work, swap it for a warm one.

Is a propane heater safe in a shanty or blind?

It can be, if it's the right heater and you follow its manual. Every propane flame makes carbon monoxide (CO), and every flame uses up oxygen. The danger comes from running a heater in a small, tight space without fresh air, or from using a heater that was never meant to go inside.

Use a heater rated for indoor use

Mr. Heater lists the Little Buddy, Portable Buddy, Hunting Buddy and Big Buddy as indoor-safe. They have two safety shut-offs:

• An oxygen depletion sensor (ODS), which shuts the heater off if the oxygen in the air gets too low.
• A tip-over switch, which shuts it off if it's knocked over.

A Minnesota report to the legislature noted that most portable propane heaters are approved for outdoor use only and lack these safety systems. Tank-top heaters and other outdoor heaters don't belong in a shanty or a closed blind. The same goes for camp stoves, grills and lanterns. The CPSC says never to use fuel-burning camping equipment indoors unless it's made for enclosed use, and never to burn charcoal in a tent or vehicle.

An indoor rating still needs fresh air

The ODS is a backstop, not a CO detector. The Buddy manual warns that without enough combustion and ventilation air, the heater "may give off excessive CARBON MONOXIDE." Its rules for inside use:

• At least 9 square inches of fresh air opening, like a 3 by 3 inch vent or a cracked window.
• If the enclosure has no window or roof vent, don't use the heater inside it.
• Never run it while sleeping, and never in a moving vehicle.
• Keep it 30 inches from anything above it, 24 inches in front and 6 inches on the sides. In a fabric blind, that means well away from the walls, the roof and your gear.
• Disconnect the cylinder when the heater isn't in use, and don't store spare cylinders near it.
• Above 7,000 feet it may burn dimmer or shut off. If it shuts off, get fresh air in, wait 5 minutes and relight.

Know the signs

The CPSC lists headache, dizziness, weakness, nausea, vomiting, drowsiness and confusion. It feels a lot like the flu, without a fever. If anyone feels that way, shut off the heater, get everyone outside and get medical help. The CPSC estimates about 170 people die in the U.S. every year from CO made by consumer products other than cars, and the Minnesota Department of Health counted four ice shelter deaths from CO between 2015 and early 2019.

CO alarms: the one thing you can't skip

You can't see, smell or taste carbon monoxide, so an alarm is the only warning you'll get. The Minnesota Department of Public Safety's advice for ice houses:

• Bring a battery-operated CO alarm made for the ice house. Don't just carry your home alarm out there.
• Change its batteries more often than your home alarms, because cold drains them fast, and carry spares.
• Don't wait to smell gas. CO can reach deadly levels in an ice house in less than 20 minutes.

Look for an alarm listed to UL 2034, the standard the CPSC points to, and check the operating temperature on the box. Many home alarms are made for ordinary indoor rooms. First Alert's CO400 manual, for example, says it's meant for "ordinary indoor locations of family living units." An ice house or blind on a zero-degree morning is not that, so choose one rated for the cold, or keep it inside your coat until the shanty warms up.

If it goes off, the CPSC says don't go looking for the cause. Get out into fresh air, call 911 and count heads.

Setting up a heater safely, step by step

1. Read the manual for your exact heater and check the hose and connection for damage.
2. Hang or set the CO alarm first, at about head height where you sit, and press the test button.
3. Open your vents. At least 9 square inches for a Buddy. A pop-up shelter's vent windows or a cracked door on a hard-side house both count. Don't block vents with snow or gear.
4. Set the heater on a flat, stable surface with its clearances, out of the walkway.
5. Light it, warm up on high, then turn it down to low. You'll double your run time.
6. Swap cylinders outside if you can, with the heater off.
7. Shut it off and disconnect the cylinder when you leave, and before anyone dozes off.

Compare indoor-rated heaters on our propane heaters page. Running a flasher too? See our fish finder power guide.

Questions people ask

How long does a 1 lb propane tank last in a Mr. Heater Buddy?

Mr. Heater says about 3 hours on high (9,000 BTU) and about 6 hours on low (4,000 BTU). Our math from the propane's energy gives about 2.4 and 5.4 hours, and the cold can cut that further. Our calculator does it for any heater.

Can you sleep with a Buddy heater on?

No. The Buddy manual says never to operate it while sleeping, and the CPSC says not to use portable heaters while sleeping in tents, campers or vehicles. Turn it off before anyone goes to sleep.

Why does my Buddy heater go out before the cylinder is empty?

Cold. Propane boiling into gas chills the cylinder, and a small cylinder can't warm back up fast enough, so the pressure drops. Start with warm cylinders or switch to a 20 lb tank with Mr. Heater's hose and filter.

Can I hook a Buddy heater to a 20 lb tank?

Yes. Mr. Heater says the Portable Buddy connects to a 20 lb cylinder with its optional hose and filter. On low, a full 20 lb tank works out to around 100 hours.

Can I refill 1 lb propane cylinders?

They're sold as disposable, and the Buddy manual calls for 16.4 oz disposable cylinders. Refill kits exist, but we don't recommend refilling them, especially for a heater you'll run in a closed space.

Do I really need a CO detector in my ice house or blind?

Yes. It's the only way to know CO is building up. Minnesota's public safety officials say to bring a battery alarm made for the ice house, change its batteries often and carry spares.