Propane Heater in the Garage? Fumes, Damp and Frozen Bottles

Your workshop is freezing and a propane heater promises fast, portable warmth. But is it safe with the door shut, and why is everything suddenly damp?

Ventilate well, burn propane rather than butane in the cold, and match the bottle to the heater. PartsForMachines lists 32 SIP, Sealey and Draper gas heaters in its propane heater range, from bottle-top warmers to 117kW warehouse heaters.

Is It Safe to Run a Propane Heater With the Garage Door Shut?

No, not unless the garage is properly ventilated. A portable propane heater takes its oxygen from the room and leaves all of its exhaust there. That exhaust is mainly carbon dioxide and water vapour, but carbon monoxide can build up if the burner is short of air or not burning properly, and you cannot see or smell it.

Heaters such as the RP15 radiant propane heater are made for small workshops and garages with good ventilation. Check the manual for the ventilation it needs: the LP100’s, for example, asks for a permanent opening of 25cm by 25cm for every kW of output. Keep air moving through, and fit a carbon monoxide alarm.

Why Does My Workshop Get Damp When the Propane Heater Runs?

Because burning gas makes water as well as heat. Water vapour and carbon dioxide are the main products of combustion, and a portable heater releases all of that moisture into the workshop air, pushing the humidity up.

The water then condenses on anything cold enough to chill the air below its dew point: windows, a concrete floor or the bare cast iron of a machine table. Ventilate so the damp air can escape, protect bare metal, and for a room full of machine tools consider an electric heater, or a flued one that vents outside.

Propane or Butane: Which Gas Works in a Cold Garage?

Propane. It boils at about −42°C, so it keeps turning to gas in a freezing garage. Butane boils at around 0°C, so it struggles to vaporise once the bottle is that cold. Nearly every heater in this range burns propane.

The exception is the CH4200 cabinet gas heater, an indoor heater for rooms such as a home office, which holds a 15kg butane bottle in its back. Only ever connect the gas a heater is built for: the CH4200’s instructions, for example, rule out propane.

How Long Will a Propane Bottle Last on My Heater?

Divide the gas in the bottle by the heater’s hourly use. A 13kg bottle, for example, on the 47063 10kW jet heater, which burns up to 0.74kg an hour, lasts nearly 18 hours at full output.

Bigger heaters use far more. The 1706 burns about 3.63kg an hour, so the same bottle lasts about three and a half hours, and the 3711DV takes up to 6.89kg an hour. Small ceramic heaters sip gas: 0.22 to 0.33kg an hour on the LP13. Drawing gas that fast can also make a bottle ice over, so match a big heater to a big cylinder, or two linked together.

What Should I Check Before I Buy?

• how fresh air will get in and fumes get out, plus a carbon monoxide alarm
• the gas: propane for a cold workshop, and only the gas the heater is built for
• hourly gas use in kg against your bottle size and running hours
• the power it needs: none, a mains socket, a 110V site supply or a battery
• its safety devices, such as flame-failure, tip-over and overheat cut-outs

Not sure which heater suits your space? Contact the PartsForMachines team by WhatsApp, telephone or email with its size, how it is ventilated and the gas bottles you use, or browse the propane heater range.

Product options, delivery options and returns terms are shown on each product page. A 30-day return policy applies to eligible items.

Frequently Asked Questions

Are heaters that sit on top of the gas bottle safe?

They can be, if you follow the manual. The 07866 bottle-mounted heater, for example, clamps onto the rim of a 7 to 15kg propane cylinder. Keep the bottle upright and secure, well clear of anything that burns, and ventilate as for any gas heater.

Why does my heater go out when I let go of the button?

Often the flame-failure device is doing its job. Some heaters need the gas button held after lighting until the thermocouple has warmed up; one maker asks for 30 to 60 seconds. Follow your manual’s timing, and if it still goes out, work through its troubleshooting.

Can I use a barbecue regulator on a space heater?

No. Use the regulator that came with your heater, unaltered: every heater in this range is supplied with one. Small ceramic heaters such as the LP13 use a 37mbar fixed regulator. After connecting, check the joints with soapy water or leak-detection spray, never a flame.

Should the gas bottle stand inside or outside the workshop?

Store spare bottles outside in a well-ventilated spot, away from drains: propane is heavier than air, so escaping gas sinks into drains and low corners. Keep the bottle in use upright, at the distance the manual gives, and never in the heater’s hot-air path.

Is it safe to warm a frozen gas bottle?

No. Never heat a gas cylinder for any reason: heat raises the pressure inside, and an overheated cylinder can rupture. Ice on the bottle means gas is being drawn off faster than the bottle can supply, so use a larger cylinder or two linked together.

Is it normal to smell gas when the heater starts?

A brief whiff as it lights can be normal: the LP55, for example, gives only a short scent at start-up. A lingering smell can mean a leak. Turn the gas off at the bottle, ventilate, avoid flames and switches, and get it checked before reuse.

Does a propane heater need mains power?

Fan heaters need power for the fan: a mains socket, a 110V site supply on dual-voltage models, or an 18V battery on the 09269 cordless propane heater, which runs up to 8 hours per charge. Radiant heaters such as the RP15 need none.

What fire risks does a propane heater bring into a workshop?

The open flame and hot outlet are the danger. Keep petrol, solvents and other combustibles well away, leave the clearances the manual gives around the heater and in front of its outlet, and switch it off before spraying or sanding.

Can I turn the heat down to save gas?

On models with variable output, yes. The 2261DV runs from 31.4 to 66.2kW, burning 2.10 to 4.27kg of propane an hour, and the DV85 from 16.1 to 24.9kW at 1.16 to 1.79kg. Check the spec for a variable output range.