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Gas heaters are generally safe, but an unreliable heater could cause a fire or emit harmful gases such as carbon monoxide. Having your gas heater serviced at least once every two years can protect you and your loved ones. A recall is usually issued for any gas heater that is harmful.

These days, heaters come with a variety of functions including a safety alert feature, but the first consideration you’ll have to make is which fuel source to use. Natural gas and electricity are the two most common forms. They both do the job, but each has its own set of benefits and drawbacks that could influence your selection. In this article, you are going to see various drawbacks and dangers that are common when using a gas heating system in your house. Read on to find out whether gas heaters are safe.

Why Do Many People Use Unvented Gas Heaters?

Unvented gas heaters are popular because they can heat living and working environments fast, economically, and with minimal effort. Installation of unvented heaters does not necessitate large financial investments or home modifications. Most unvented gas heaters are also silent and do not require the use of a fan. These characteristics may make them appealing to you as a homeowner, but let’s be clear: they are hazardous. However, even with proper maintenance and adherence to safety guidelines, unvented gas heaters have their risks.

The Risks Of Using Gas Heaters Without Ventilation

Unvented gas heaters are associated with three principal risks: fire, excessive humidity, and health dangers caused by your gas heater’s fumes, water vapour, and pollutants.

Fire Hazards

The threat of fire is the most evident disadvantage of unvented gas heaters. The most common causes of house fires are improper installation, location, and maintenance of these heaters. In smaller settings, these heaters could still be a fire hazard if you place them directly on rugs or carpets, very near to a wall, or near combustibles like furniture, fabrics, or paper. In addition, letting them operate for an extended period or running them unattended, especially if you have pets or children, can lead to house fires too.

Moisture Damage

In addition, unvented gas heaters produce unwelcome amounts of dampness and condensation. This condensation is caused by the heater’s efficiency and the subsequent release of methane into the room. Since there is no venting to capture the water vapour created during the heating process, they escape into the outside air. When you add far too much dampness to a space, it might lead to the following:

  • Wooden furniture can be prone to warping and decay.
  • Paint and wallpaper may start to bubble and peel.
  • Mould could grow on the plaster.
  • You and your household members might experience serious health issues, particularly if they suffer from allergies or asthma.

In order to reduce humidity in the air, you must reduce your gas heater’s efficiency from around 99 per cent to 90 per cent (by enhanced ventilation).

How Unvented Gas Heaters Are Hazardous To Your Health

Natural gas and even propane heaters have a substantial impact on indoor air quality, which can be a serious health hazard. To efficiently eliminate pollutants like carbon dioxide as well as carbon monoxide from your space, ventilation is required. On the other hand, unvented gas heaters lack this option, making them unsafe.

Carbon Monoxide (CO)

Low quantities of carbon monoxide cause long-term health problems. It is poisonous and even lethal in greater concentrations. Carbon monoxide is an irritant-free, odourless, colourless, and invisible gas that can only be detected using carbon monoxide detectors. Carbon monoxide is the most common fatal gas, causing organ damage, lifelong brain damage, and ultimately death. Carbon monoxide poisoning caused by unvented gas heaters kills about 200 people each year.

Carbon Dioxide (CO2)

While carbon dioxide is not harmful, it does offer several health hazards. Headaches, dizziness, restlessness, weariness, high blood pressure, hypoxia, and, in severe forms, convulsions and comas are all symptoms of increased carbon dioxide exposure.

Nitrogen Dioxide (NO2)

Even when you are just exposed to low quantities of nitrogen dioxide, it can damage your immune system and make you more susceptible to respiratory diseases. Because nitrogen dioxide is continuously formed in a flame, it has been linked to increased cases of asthma, coughs, sore throat, nausea, and vertigo. Chronic lung damage, such as emphysema may result from long-term exposure to this gas.

Sulphur Dioxide

Some carbon molecules create soot when gas does not burn entirely, indicating the presence of carbon monoxide in your space. When using natural gas in an unvented gas heater, methyl mercaptan is introduced into the solution. It gives off a sulphuric rotten egg odour that alerts you to the leak. When methyl mercaptan is burned, sulphur dioxide is produced, which can irritate your eyes and respiratory tract.

Furthermore, a visible residue can be left on the walls, indicating that the region has been contaminated. Yellow and brown residues are the result of contaminants from your gas heater reacting with tobacco smoke, animal dander, and polyurethanes present in furniture and carpeting. Grey residues are the result of the same contaminants reacting with the non-organic air fresheners’ chemical compositions and wax. Black residues are a prominent sign of soot created by incomplete combustion in the heater. Still, they can also be caused by debris accumulated on the outside and the top of your heater, including lint and dust.

Although unvented gas furnaces appear cost-effective and efficient, these characteristics are merely a ruse due to poor ventilation. Because of the health risks associated with the long-term use of these types of heat sources, some states are starting to prohibit their use in all new residential construction. In addition, they are mandating that existing systems in older homes be adequately maintained in approved places or removed entirely.

How To Make Unvented Gas Heaters Safer

Most unvented gas heaters are small units designed for emergency usage or use in small areas, such as a single room. Some versions include options for ducting or fans with less ducting. They are frequently made available as furnishing and cabinetry. They can be wall-mounted or utilised as fireplace additions to mimic the look and feel of a typical wood fire; most have heat outputs ranging from around 5,000 to about 30,000 Btu/hour. This fuel-powered heat source may be a great backup heat source, making it an attractive alternative for some households. Follow the guidelines below if you opt to install an unvented fuel heater in your home.

Use Oxygen Sensors

Only certified unvented gas heaters are recommended for use. Oxygen Depletion Sensor (ODS) pilots will be installed on approved heaters, which will switch off gas flow whenever oxygen levels in the space fall to around 18.5 per cent or lower. For comparison, typical air levels hover about 21%.

Use in Appropriate Spaces

A professional installer, once again, might be able to identify the best heating unit for your room; their expertise is priceless. Experts have strongly advised against using a gas heater that is too big for any given room. Because unvented gas heaters are primarily intended for supplemental heating, they should not be used for more than 4 hours at a time and should not be used in compact, poorly ventilated locations like restrooms or bedrooms.

Is It Safe To Use Portable Gas Heaters Indoors?

If you have a mobile outdoor gas heater, you should never use it indoors. It is not safe to use outdoor portable gas warmers indoors since they lack the necessary emission control elements. Some argue that utilising a portable heater indoors depletes oxygen levels in that space. In addition, when using outside gas heaters indoors, more people complain about lack of oxygen rather than carbon monoxide poisoning. However, carbon monoxide exposure is a far more serious threat.

Inside use of portable gas heaters is safe, presuming we are talking about gas bayonet heaters designated for indoor use. There are also portable heaters only meant to be used in outdoor spaces, like your patio. As previously stated, you should never operate an outside gas heater indoors because they are not suited for indoor use. Portable gas heaters for indoor use are quite safe. Outdoors, portable gas heaters are also quite safe to use. Using an outside propane portable heater indoors, on the other hand, is a horrible decision that can be both harmful and tragic.

Common Gas Leak Signs

Gas has an awful odour that is sometimes compared to rotten eggs. Since natural gas is generally odourless, it is required by law for gas manufacturers to incorporate a substance compound mercaptan that gives the gas a unique odour. It is a dangerous scenario to be in when you smell gas, and you should act quickly. Many homeowners have lost everything as a result of gas heater explosions or other gas-related incidents. If you detect gas and can trace it to your gas heater, turn it off right away, exit your home, and contact the fire department.

Knowing how to recognise the indicators of a gas leak can keep everybody in your house safe and give you peace of mind. Teach your entire family how to recognise the indicators of an indoor gas fuel leak. Here are some of the tale-tell signs that gas is leaking from your gas heater in your house:

Is a Section of Your Lawn Starting to Wilt?

An underground gas leak could be to fault if a section of your lawn is withering (brownish, yellowish tint). Outdoor vegetation will invariably grow above the gas line on your property. Your lawn, as well as plants just above the gas line, will start to die if it is a gradual leak. Do not stay indoors if you smell, hear, or see a gas leak. If you are in an emergency, call the fire department right away. Any device that could generate a spark should be avoided. When a gas leak is discovered, the first goal is to prevent a gas fire.

Do You Get a Whiff of Rotting Eggs or Sulphur?

The odour of gas is sometimes compared to that of rotting eggs. If you detect the smell of rotten eggs or sulphur, you should not disregard it as natural gas is making its presence felt. You should follow the odour to figure out where it’s originating from and what you should do next. To be safe, exit your home and contact your local fire department for an assessment.

Is There a Hissing Noise?

If the gas leak is emanating from a pipeline or behind the wall, you might hear it rather than just smell it. When gas leaks from a gas pipe, it generates noise. If you can identify the scent and hear a sound that goes along with it, take action right away to avoid more gas from leaking.

Pros And Cons Of Using A Gas Heater To Heat Your Space


Because gas furnaces are large and sophisticated, they require skilled installation. They also need a chimney or flue to exhaust the combustion process’s pollutants. A chimney must be able to fit in your home, and if it doesn’t already have one, one must be added during installation.


A gas heater costs more to buy and install than an electric heater of equivalent size. Natural gas, on the other hand, is a cheaper source of fuel compared to electricity, rendering gas heaters more affordable to run.


With proper maintenance, gas furnaces can last for long. Electric heaters have a shorter life span.


When HVAC firms tell customers that their furnaces should be serviced at least once a year, they are talking about gas furnaces. Annual professional maintenance is essential to keep gas-fuelled heaters in good working order for many years to come.


The most serious problem associated with gas furnaces is the risk of carbon monoxide poisoning, which can be lethal in high enough concentrations. Installing a carbon monoxide sensor near the furnace will help you discover any danger. Gas leaks and fires are additional dangers that can be avoided with regular maintenance.

What Are The Signs And Symptoms Of CO Poisoning?

The following symptoms are most typically associated with carbon monoxide exposure:

  • Headaches
  • Dizziness
  • Nausea
  • Flu-like symptoms and exhaustion
  • Exertion causes shortness of breath
  • Impaired decision-making
  • Pain in the chest
  • Confusion
  • Depression
  • Hallucinations
  • Agitation
  • Vomiting
  • Pain in the abdomen
  • Drowsiness
  • Changes in appearance
  • Fainting
  • Seizures
  • Trouble with memory
  • Problems with walking

Which Groups Of People Are The Most Vulnerable To CO Poisoning?

Carbon monoxide poisoning can affect anyone. Because of poorly managed or ducted heating systems, risks are higher in the winter. The following people are at the greatest risk:

  • Unborn children
  • Infants
  • Adults in their later years. Adults 60 years and older are the most common victims of CO poisoning.
  • People who live at high elevations.
  • People suffering from chronic heart disease, anaemia, or breathing issues.
  • People who already have high CO concentrations in their bodies, such as smokers.

Reach Out To A Professional To Fix Any Gas Heater-Related Issues

Are gas heaters safe? Well, gas heaters should never be used in your kids’ rooms because they can cause carbon monoxide to build up if the room is not adequately ventilated. As you have read in this article, gas heaters can pose a lot of dangers to you and your family. Therefore, heating systems should be repaired and vents should be cleaned regularly. Keep the door slightly open for ventilation while using a gas heater in any room. If you see any signs of a gas leak or any problem concerning your gas appliance, call a professional to fix it for you before you put yourself and your loved ones in danger.


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