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What Causes Black Smoke Coming from Your Patio Heater

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Patio heaters can make time spent outdoors more enjoyable but knowing the right way to use and maintain one can require some homework on your part. A common issue people with propane-powered patio heaters face is the appearance of black smoke while theirs is in us. 

Three things can cause black smoke to come from your patio heater:

  • An improper gas mixture is changing how the heater burns propane.
  • Substances on the exterior of the heater are being burned off.
  • Interior debris and corrosion are being burned.
patio heaters on back deck

Within each of these three categories, there are actually several more specific causes, from faulty parts to poor maintenance. We’ll be going over how properly functioning patio heaters are supposed to work and breaking down issues you may see in your own heater.

Why Black Smoke from Your Patio Heater Can Be Dangerous

As you likely know from firing up a propane grill at a barbecue, if a propane-powered flame is producing black smoke, there’s a problem. Propane is what’s known as a “clean burning” fuel, which means that it doesn’t produce any harmful emissions (aka black smoke) when burned.

Not only is this good for the environment, but it’s good for your health, too. When burned or combusted, other fuels like gasoline in your car produce hazardous emissions that are dangerous for you to inhale either directly or indirectly on a regular basis.

Because of the specific chemical reaction occurring when propane is burned, propane-powered appliances like your patio heater are safe to use regularly if the heater is functioning properly. Under proper conditions, combusted propane produces carbon dioxide and water vapor, both of which are safe to have in the air around your patio.

However, if you have black smoke coming from your patio heater, that’s a clear sign that either something else is burning alongside the propane or when propane isn’t being burned efficiently. In the next section, we’ll go over how the latter can happen and what you can do to fix prevent this cause of black smoke from your patio heater.

Propane Heaters Run on a Specific Oxygen Ratio 

Although propane is largely known as a “clean” fuel, that doesn’t mean it never produces smoke. Propane-powered appliances rely on specific parts to control the ratio of gases supplied to the ignition source. When the correct amount of specific gases is provided, then fuels can burn efficiently.

In most cases, the key gas is oxygen. Without enough oxygen, fuels can undergo what’s known as “incomplete combustion.” When this occurs with propane, the resulting black smoke can be very dangerous for the health of you and your family.

While normal propane combustion produces water vapor and carbon dioxide at safe levels, incomplete propane combustion produces carbon monoxide instead. Inhaling significant amounts of this gas, whether all at once or over time, can be harmful to your health in the short and long term.

Symptoms of carbon monoxide poisoning can be as innocuous sounding as a headache and moderate dizziness all the way up to such as:

  • Blurred vision
  • Difficulty breathing
  • Falling unconscious 

When exposed to carbon monoxide in an open-air environment like a patio, your risks of serious damage are certainly lessened, but there can still be cumulative effects from low to moderate levels of exposure. Fortunately, the color and appearance of your patio heater’s flame can give you a good indication of whether an improper gas mixture is causing any black smoke you see.

How to Know If Your Heater Has an Improper Gas Mixture

Apart from the black smoke itself, changes in the appearance of your patio heater’s flame can be the best indicator that the propane to oxygen ratio is improperly regulated. While having too little propane can cause changes to the flame’s appearance, that’s unlikely to cause black smoke, so we’ll focus on the other end of the spectrum.

If there’s too much propane relative to the amount of oxygen, the flame produced will be much larger than normal. Another tell-tale sign is that the majority if not all of the flame will have a yellow to golden color. 

When burned at the right gas ratio, propane-powered flames are supposed to have an inner core of yellowish-orange color with the outer portion a medium blue color. Think of what you’d see when turning on a gas-powered stove. If your patio heater’s flame is significantly more yellow than that, it is running on a low ratio of propane to oxygen.

Pinpointing the Issue Causing Improper Gas Mixtures

There are two main parts of your patio heater that could be causing the ratio of propane and oxygen:

  • The air mixer valve
  • Gas regulator

Either (or, however unlikely, both) of these parts could be malfunctioning and producing an improper gas mixture that causes your patio heater to emit black smoke. Depending on which part is causing the issue, there are different fixes for each.

Obviously, if either part is faulty, it will need to be replaced. However, if the issue is the air mixer valve, it may not be an issue of the individual part that you put in but rather the model. 

If you ever replaced the air mixer valve yourself, you may have thought that any model would do, when actually propane-powered appliances often require specific models to get the correct gas ratios. Make sure that any replacement air mixer valve you’ve installed actually meets the specifications outlined in your patio heater’s owners’ manual.

On the other hand, if the improper gas mixture is coming from a malfunctioning gas regulator, the issue could be caused by an incorrect pressure adjustment. To effectively regulate the amount of propane released into the propane burner, the gas regulator needs to be calibrated first, a process you can either have done by a profession or reference your owners’ manual to doublecheck yourself.

Substances Burned Off the Exterior of Your Heater

If you’ve eliminated an improper gas mixture from the list of potential causes of the black smoke, that means that additional substances are being burned alongside the propane in your patio heater’s fuel tank. 

In this section and the next, we’ll be discussing the most likely exterior and interior sources of debris that could be producing any black smoke you see. In either case, the most effective way you can combat this issue if with proper maintenance of your patio heater. 

However, in some cases, seeing black smoke is normal and not indicative of any problems that you need to fix, as we’ll get into first.

Black Smoke Is Common When First Using a New Heater

One of the most common times that patio heaters will produce black smoke is when they are first used. This can be disconcerting to new owners, who may have been sold on the clean-burning aspect of a propane heater, but it’s actually quite common.

When manufacturing and put together, many patio heaters will still have lubricants and oils on them that were transferred during the production process. When this happens, the first time that new owners ignite their patio heaters, black smoke is produced when this residue burns.

You’ll be able to tell whether this is a “surface” issue or an ongoing problem based on how long the black smoke persists. Generally, black smoke produced from burning off manufacturing-related substances should only last the first thirty minutes after you start using your heater.

If your problem persists longer than that, the issue may still be from substances on the exterior of your heater but just not ones that can be attributed to how recently you bought it.

Check that Your Burner and Ports Are Clean

Over time, the propane pilot and burner on your patio heater can build up carbon sediment. This usually happens when the burner isn’t cleaned regularly, as this is a problem that makes itself worse over time. 

When a small amount of carbon sediment accumulates, it makes it harder for the gaseous byproducts of propane combustion to escape. Specifically, the carbon dioxide produced has nowhere to go, so it becomes black sediment that accumulates on the burner and the ports. 

The more this happens, the harder it is for carbon dioxide to dissipate, and the more sediment builds up over time. You can quickly solve this problem by wiping down the burner or following whatever cleaning method is described in your owners’ manual. 

The most difficult issues arise when sediment in the ports have hardened and become clogged. In such cases, you may need to use something like a paperclip to break up and remove the sediment.

If you’re still having issues with black smoke after you’ve checked the potential cause of black smoke that we’ve gone over so far, you make be dealing with substances built up internally in your patio heater.

Check Internal Issues Your Patio Heater May Have

As we’ve discussed already, sediment can easily build up on the exterior of your patio heater and cause black smoke. But if you let this go on for too long, the sediment can actually end up inside critical parts of your patio heater as well.

The propane in your patio heater will be housed in its own storage tank. To reach the burner, the propane will have to pass through the gas regulator. Then, the air allowed in via the air mixer valve and the propane both enter the burner through a specific tube, which is known as the burner venturi tube.

This tube can also be blocked up when insects or spiders crawl into your patio heater and leave debris, such as spider webs. When you turn on your patio heater, whatever is in the burner venturi tube is what is getting burned right along with the propane, producing the black smoke that you see.

To clean this tube, you’ll need to take apart your patio heater, a step that you’ll again want to reference your owners’ manual to make sure you both dismantle and reassemble everything properly. Once removed, the tube should be thoroughly cleaned with a pipe cleaner.

Other internal parts connected with the burner venturi tube will also likely have similar debris and/or sediment. Generally, you can safely clean these parts using compressed air canisters. To be safe, make sure not to directly apply the compressed air from a close range.

Regular Maintenance Lessens the Chance of Black Smoke

Now that you know the several ways that your patio heater can produce black smoke, it should be pretty clear just how key proper and regular maintenance is. In most cases, identifying and fixing the cause of black smoke can be fairly straightforward, but you can often prevent these issues from ever happening in the first place.

First, you should make sure to schedule thorough yearly maintenance of your patio heater where you inspect, clean, repair, and recalibrate all its parts as necessary. While your owners’ manual will have more specific instructions, in general, you want to:

  • Check that the gas regulator is still calibrated for the correct pressure
  • Thoroughly clean or replace all internal parts, like the burner venturi tube and pilot feed tube
  • Replace burner/pilot that appear worn out or require replacing according to manufacturer instructions
  • Check the propane level and perform leakage tests

Performing yearly maintenance will help you avoid black smoke from your patio heater and lengthen its lifetime. A great time to take care of it, is right before whatever time of year you use the heater the most. But that alone is not enough. To be a responsible owner, you also need to be diligent each time you start and finish using your patio heater.

Make sure that you inspect the visible connections when you’re ready to ignite and turn off the heater. Also, wiping down the burner and its ports before and after each use is a great way to reduce the chance of harmful build-up. 

Not only will this lessen the chance of black smoke, but it will reduce the amount of sediment that makes it into the interior of your patio heater and the amount of time and money you spend cleaning and/or replacing the inner tubing.

Proper Storage Also Helps Minimize the Chance of Black Smoke

On top of proper maintenance, you also need to pay attention to how you store your patio heater. Beyond just avoiding the production of black smoke, proper storage is important to make sure your patio heater lasts a long time and is used safely.

As we’ve gone over, one of the biggest overall causes of black smoke is built-up sediment and debris, whether external or internal to a patio heater. While normal use of your patio heater can result in carbon sediment, the dust that settles on an unused patio heater can be just as problematic.

When you’re not using your patio heater, make sure to store it in a secure place with a secure cover surrounding it. A well-secured cover can prevent dirt from accumulating on the burner and ports and reduce the number of insects and spiders that could make their way inside its parts.

Storing your heater this way will also help reduce the chance of any water accumulating inside it, which can make it easier to get a flame going even on days following heavy rain. Finally, for safety, you also want to make sure to fully turn off the patio heater and use the propane manual shut off whenever no one is on the patio or within sight of the patio heater. 

As easy to use and enjoyable as patio heaters are, it’s still important to keep in mind that they can be serious consequences to not using and storing them properly. Following these suggestions will help make sure that you’re doing so in a way that allows you to enjoy your patio heat for as long and as safely as possible.

Conclusion

We’ve discussed several possible reasons that your patio heater is producing black smoke. While the various causes may seem like a lot to keep track of, avoiding these potential issues can be straightforward if you know what to expect and build regular maintenance and proper storage into your routine.

Remember, every time you get ready to use your patio heater:

  • Wipe down the burner and ports with a clean cloth.
  • Keep an eye out for overly yellow flames in the burners to make sure the gas ratio isn’t off.
  • Have another cloth on hand to wipe down the patio heater after you’re done using it.
  • Completely turn off the ignition knob and then use the manual shut off for the propane tank.
  • Cover your patio heater until next time.

If you make sure to follow these steps, your regular routine will allow you to rule out possible causes if you do see black smoke again. In case that happens, you’ll be more familiar with your patio heater and be ready to handle the issue promptly to keep your heater in good condition and you and your family safe. 

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Jena Slocum Co-Founder

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