I have one of those tall propane outdoor heaters.....( fumes)?

shoul be ok,,bit to be on the safe sd i would get a co detector ,they are cheap

Hi bfhwm50, ChrisFixit from the Atlanta Home Depot here. While I understand your desire to keep your plants warm during the winter, from a safety stand point this is probably not one of the better ways to go about it.

As the previous answer stated there is the possibility of gas buildup, also with an active flame in an enclosed area like a garage there are any number of undesirable possibilities, including gas fume ignition. A much safer option would be to still store the plants in the garage and cover them with a "Frost Protek" plant cover. These covers are of the same type that commercial plant houses use and have a rated protection at temperatures as low as 30 degrees.

If you do go forward with the idea of using a patio heater please make sure you leave a garage door or window ajar to allow venting, employ the use of a Carbon Monoxide detector, also after turning on the heater set your self an alarm to remind you to go out and turn it off. I hope this has been helpful and good luck.

Cheers,

ChrisFixit

You need to consult the CERTIFIED operating instructions of any heater you attempt to use for this area to ensure it is suitable for that application. If it is not certified for indoor use and it causes a fire or hurts anyone, the manufacturer will take no responsibility and insurance companies will deny any claims because the heater was used "In a manner other than what it was intended".

If this is a patio heater, I think I can safely say that Yes, it would be dangerous to use it. The legal ramifications aside, the burner on those heaters is fairly high up and you don't want that anywhere near the buildings ceiling structure.

As a general comment, you need to make sure you have enough fresh air for an appliance to operate safely and efficiently. A propane burning heater requires combustion air to burn properly, but it also requires ventilation air to allow the products of combustion to escape. Propane burns clean, but if you REBURN those products of combustion you make carbon monoxide in a big way!

The general rule of thumb we use in the industry is 1 square inch for every 1000btu's. So if it is a 20,000 btu heater you need to have at least a 2" x 10" (or 20 square inch) opening for safe and proper operation. That doesn't mean propping a door open, or opening a window in the area. These can easily be shut, cutting off the fresh air supply.

I recommend you look at a direct vent wall furnace like an Empire DV35 or something for this application. Direct vent means that they draw air from outside, burn it with the fuel and then put the products of combustion back outside. They are not cheap, but it's the safest way to go.

Hope this helps!