Does Propane (LPG) Heat Produce Carbon Monoxide?
Carbon monoxide – CO – is a toxic gas.
Natural gas or propane (LPG) appliances can produce carbon monoxide when they burn with incomplete combustion.
Properly functioning gas appliances produce little, if any, carbon monoxide.
Complete and Incomplete Combustion
Propane – LPG – burns within its limits of flammability.
The lower and upper limits of flammability are the percentages of LPG that must be present in an LPG/air mixture.
This means that between 2.15% and 9.6% of the total LPG/air mixture must be LPG in order for it to be combustible.
However, the optimal mixture is 4% LPG/air. So, 4 parts LPG (propane) to 96 parts air.
With complete combustion, the burner produces a blue flame.
So, richer mixtures, those closer to 9.6%, are likely to suffer from incomplete combustion.
A yellow flame, the collection of soot and excessive water vapour condensation are three physical signs of incomplete combustion.
The natural gas – methane – limits of flammability are different, at 5.4% to 17%.
The optimal combustion mixture for methane is also different, at approximately 10.42%.
Combustion Formula Equation for LPG - Propane
In the presence of sufficient oxygen, LPG burns to form water vapour and carbon dioxide, as well as heat.
Formula Equation for Complete Combustion of LPG - Propane:
Propane + Oxygen → Carbon Dioxide + Water + Heat
C3H8 + 5 O2 → 3 CO2 + 4 H2O + Heat
If not enough oxygen is present for complete combustionof LPG, incomplete propane combustion occurs with water, carbon dioxide, and carbon monoxide being produced.
Formula Equation for Incomplete Combustion of LPG - Propane:
Propane + Oxygen → Carbon Dioxide + Carbon Monoxide + Water + Heat
2 C3H8 + 9 O2 → 4 CO2 + 2 CO + 8 H2O + heat
Combustion and Carbon Monoxide (CO)
All gas appliances, domestic and industrial, produce water vapour, Carbon Dioxide and heat, and usually very small amounts of Carbon Monoxide.
If installed and maintained correctly, the operation of the gas appliance provides quick and efficient heating, cooking, hot water and more, and the products of combustion do not create any hazardous situations.
If an appliance is not correctly installed and maintained or has been modified, the products of combustion might change, and become hazardous to the people around the appliance.
Something as simple as a ventilation change (getting fresh air to the appliance to sustain complete combustion) may cause a gas appliance to malfunction, and create a hazardous situation for the people around.
Sometimes it is obvious when a gas appliance malfunctions.
Sooty smoke, red or yellow flames or poor performance are indicators, but sometimes no indicators are obvious.
If Carbon Monoxide (CO) is produced and escapes the appliance into the surrounding air, it will not be obvious (no smell and no taste) but will be very dangerous.
It is essential that gas appliances are correctly installed and serviced every two years, to maintain good combustion and safe, efficient operation.
Using Approved Appliances and Gas Fitters
Australia has some of the most stringent standards on gas appliance combustion emissions of any country in the world.
This makes our indoor gas heaters very safe to use.
The gases of primary concern are CO (carbon monoxide) and NOX (nitric oxide and nitrogen dioxide).
These gases can be produced during combustion.
To be certified for use in Australia, indoor gas heaters must meet or surpass these strict standards.
Only buy or use Australian tested, certified and labelled gas appliances.
Make sure your gas appliances are installed by a licensed gas fitter and that you have adequate ventilation.
Finally, when you use your gas appliances, always read and follow the manufacturer’s instructions.
Don't Use Outdoor Gas Heaters Indoors
The same requirements are not applicable to outdoor heaters and appliances.
Because they are intended for outdoor use, with unrestricted ventilation, they are not required to meet the indoor heater emission standards.
This includes heaters, BBQs, pizza ovens and all other outdoor appliances.
If a gas appliance has been marked for outdoor use only, do not use it indoors or in partially-enclosed areas without adequate ventilation.
Gas Appliances Maintenance
This can vary by manufacturer and appliance model.
It is important that your gas appliances are only service by qualified technicians.
In most cases, this means a licensed gas fitter or a factory technician.
Good maintenance helps ensure proper combustion and minimal CO generation.
Key warning signs that your gas appliance requires servicing are a yellow or red flame, a flame with a yellow burning tip, the accumulation of yellow/brown soot around the appliance, pilot lights that frequently blow out or an acrid smell and eye irritation.
The exceptions to this are gas fireplaces and gas log fires that are designed to have yellow flames.
The above signs may be indications of incomplete combustion.
The result is that you could be wasting gas and/or generating carbon monoxide.
The latter is a serious safety problem, if it occurs with an indoor appliance.
If you observe any of these warning signs, you should schedule a service ASAP.
Detecting Carbon Monoxide
Carbon monoxide is colourless, odourless and tasteless.
CO is slightly less dense than air, so it rises.
It is considered toxic when encountered in concentrations above about 35 ppm.
It is lethal in 30 minutes at 4,000ppm. It drops to 5 minutes at 5,000ppm.
Health symptoms of CO poisoning includes headaches, nausea, dizziness, shortness of breath, light-headedness and loss of consciousness.
If you experience any signs of carbon monoxide poisoning while operating any gas appliance, you should stop using it immediately, move to an area where you can breathe fresh air and seek medical attention.
If you smell gas, it is not carbon monoxide, it is the odourant added to natural gas or LPG.
You should immediately deal with the leaking gas.
Turn off the gas and ventilate the room, if safe to do so.
The best way to detect carbon monoxide is with a CO detector.
These can be purchased from many retailers, including hardware stores, as well as from online merchant.
At the time of this writing, at least one major hardware chain and various online merchants had a choice of models, for under $50 each.
When used and maintained correctly, indoor gas appliances are very safe.
Just remember to never use outdoor gas appliances indoors.
There is nothing like the warmth you get from a gas heater, the fun of cooking with gas or the beautiful warmth of a gas fireplace. Enjoy!
The information in this article is derived from various sources and is believed to be correct at the time of publication. However, the information may not be error free and may not be applicable in all circumstances.