Gas Fireplace Insert Smells Like Burning Plastic? (Fix It Now!)

HK Sloan
by HK Sloan

When it comes to gas appliances, you should always be aware of any lingering smells. Odors like kerosene, burning hair, burning plastic, or rotten eggs can not only be unpleasant, but they could be dangerous. And although gas fireplace inserts are safer than wood-burning fireplaces, it’s crucial to maintain and service them regularly.

A gas fireplace insert is a metal box that you can install in your existing fireplace. It’s more like a metal box inside of a bigger metal box. As heat is generated between the two metal boxes, the insert will radiate heat. It’s normal to smell gas or residual smells during this process, but the odor shouldn’t last more than a few hours.

If your gas fireplace insert smells like burning plastic, don’t panic just yet— it’s probably nothing serious. You could be smelling factory paints and oils as they finish curing, or it could be leftover building materials as they burn. Both of these are harmless and completely normal! Just make sure to ventilate your home the first couple of times you use your gas fireplace insert.

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Difference Between Gas Fireplace and Gas Fireplace Insert

So what’s the difference between a gas fireplace and a gas fireplace insert?

Gas Fireplace

A gas fireplace has been installed where there was previously no fireplace. In essence, a gas fireplace has to be built into the house. A gas fireplace doesn’t need a chimney or existing fireplace– it only requires an exterior wall. The exhaust from the fireplace will then exit through its outer wall for optimum ventilation.

Gas Fireplace Insert

On the other hand, a gas insert is a heating element that you can insert into your existing fireplace. A gas fireplace insert is a metal box inside a larger metal box, and it releases heat as it builds between the metal boxes. You can use gas fireplace inserts in wood-burning fireplaces as a more cost-efficient option. No need to knock out any walls– gas fireplace inserts utilize the existing chimney for ventilation.

Ventless and Vented Gas Fireplace Inserts

Ventless gas fireplace inserts can be especially susceptible to “mystery” odors as the fire draws from the air circulating in your home. That means the heat could amplify any cleaning solutions, candles, or chemicals every time you turn on your gas insert. Vented gas fireplace inserts draw on the air coming into the fireplace from the chimney or flue.

Although gas fireplaces and gas fireplace inserts are both effective ways to heat your home quickly, they are different methods and will require different troubleshooting. Since you can turn on both with a switch, a gas fireplace insert may look like a gas fireplace to the untrained eye. If your gas fireplace is running in a hearth or chimney, chances are it’s an insert.

Gas Fireplace Odors

Possible Causes of Burning Plastic Smell

If your gas fireplace insert has a chemical or burnt plastic smell, there are a couple of potential culprits. It’s important to identify the cause of any odors so that you can determine if you need to take any safety precautions.

Factory Paints

If you are using your gas fireplace insert for the first time, it is likely burning off any remaining factory paints, sealants, or chemicals. Also called out-gassing, chemicals that were trapped will release once they are heated. In our case, dyes or other materials used to assemble the gas fireplace insert are being heated and released during the turn-on process.

Although out-gassing can produce undesirable odors, most residual odors produced by factory paints are harmless and will disappear with use. If you smell burning plastic when you turn on your gas fireplace insert, first open a window. If the smell persists longer than three hours, contact your gas appliance expert.

Building Materials

Since gas fireplace inserts are installed into existing fireplaces, they can react with the existing building materials. Existing building materials could be anything from adhesives to debris. For example, the mastic in your stone fireplace could be releasing odors the first few times you use your insert.

Any odors that are released during the heating process are considered normal off-gassing. Ventilate your space by opening any windows and doors. The plastic or chemical smell should circulate out within a couple of hours.

But if your gas fireplace insert is melting a foreign object, you could be breathing unsafe fumes. Turn off your main gas valve and contact a professional for assistance. Of course, always make sure a gas fireplace insert is compatible with your existing setup.

Surrounding Air Quality

If your air quality is compromised, you may experience intensified chemical odors coming from your gas fireplace. Since ventless gas inserts draw air from inside your home, any odors in the air will be sucked into your gas insert and heated. As you use your gas fireplace insert, any new furniture odors, candles, or cleaning product smells in the immediate area can be exaggerated. Although the smell can be unpleasant, it is primarily non-toxic.

If you suspect your gas fireplace insert is amplifying the smells around you, check your air quality. Remove any potential odor-causing factors, such as a new rug or oil diffuser. Remove any potential odors one by one until you have identified the cause.

Damaged Component

If the plastic burning smell lasts longer than a few hours, you could be smelling a damaged component of your gas fireplace insert. If you have fried your circuit board or a humidifier nozzle has melted, your insert will not perform as it should. Turn off the gas and contact a technician to check for signs of damage.

Solutions for Gas Fireplace Insert

Open a Window

Although a burning odor may be alarming when you first turn on your gas fireplace insert, off-gassing is standard for new appliances. Simply ventilate the area around your fireplace by opening all windows. The odor should dissipate within 3-4 hours.

Contact a Professional

Remember, it’s normal for gas fireplaces to smell for the first few uses. It could be dust, build-up, or factory paints. If you can stomach the odors, you can let them burn out for the first couple of uses. If the smell remains after ventilation, contact your service technician immediately to check for any damaged components or leaks.

Service Every Year

We applaud gas fireplace inserts for convenience and efficiency, but that doesn’t mean they don’t need to be maintained and serviced regularly. Gas inserts, when maintained properly, can last over 30 years! We recommend servicing your gas fireplace insert every year for maximum safety and efficiency.

The Importance of Cleaning Your Insert

Gas fireplaces don’t produce creosote like wood-burning fireplaces, but that doesn’t mean they are self-cleaning ovens. Gas fireplaces and gas fireplace inserts are still prone to build up. It’s important to keep your insert clean to guarantee safe operation.

To clean your gas fireplace insert, you’ll need to disassemble it. First, turn off your pilot light and gas valve (Turn clockwise). Remove the screen and logs, if any. You can use compressed air or a Shop-Vac to remove dust and build up.

If you are uncomfortable working with gas appliances, schedule a service appointment with a licensed technician. Remember, always refer to the manufacturer’s instructions and abide by local regulations.


Since natural gas is odorless and colorless, regulations require gas companies to include an additive. That additive, methyl mercaptan, creates the “rotten egg” smell that is often synonymous with a gas leak.

If you smell rotten eggs, turn off your main gas valve immediately. Open all the windows and doors to ventilate your space adequately. If the smell doesn’t dissipate within the hour, you may have a gas leak in your home.

If you suspect a gas leak, turn off your gas, exit your home immediately and call your local gas appliance expert. They will be able to determine if emergency services need to be involved.

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Related Questions

Will a gas fireplace insert work during a power outage?

Yes, most gas fireplace inserts remain fully operational during a power outage. If your insert has a standing pilot light, you don’t need electricity to turn on your gas fireplace insert. Gas fireplace inserts are a great way to keep warm when the power is out, as they are much safer than wood-burning fireplaces. 

Is it normal to smell gas from a fireplace?

Natural gas is odorless but has an additive that makes it smell like rotten eggs. It’s normal to smell gas when you turn on your fireplace, but if the odor lingers, you could have a gas leak. Turn off your gas immediately and call your service technician; they will determine the next best steps. 

Is a gas fireplace insert the same as a gas fireplace?

While they operate in the same way, a gas fireplace insert is installed in an existing fireplace while a gas fireplace is built into an exterior wall. Some people may say that they have a converted gas fireplace, but they mean they have a gas insert. Because inserts heat the surrounding masonry, strange smells could result from debris left in the previous fireplace. 

HK Sloan
HK Sloan

HK Sloan is a freelance writer currently covering DIY Home Improvement, Health, and Lifestyle. Sloan is passionate about improving situations for less, whether it be working on mind, body, or home.

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