Ventless Heating

When you need a safe, vent free heating solution in your home, garage, workshop or office, or portable heat when camping, find what you want right here!

I review all the top models of portable, ventless propane (LPG), gas and other fuelled heaters so you can see at a glance what is best for your wants and needs.

I also provide a lot of useful information about them and everything you need to know about the safety and correct way to use them to get the most from them. Let's face it, safety is a major issue when it comes to household and workplace heating as well as outdoor use when camping or filling the need for warmth on a porch or patio during the colder days and evenings.

It makes sense to start things off by taking a look at just exactly what is meant by a vent free heater and what it actually is. To do that, let's first look at why there is a need for a kind of vent to the outside for certain heaters.

What is a Ventless Heater?

ventless portable heater diagramBy ventless, I mean the heater does not have a ventilation pipe, duct or other means of allowing exhaust gases produced by the combustion process to escape to the outside of the building. On permanent fireplaces, this is achieved by a flue that runs up a chimney or via a pipe through an external wall of the building.

When there is no venting pipe, the gases produced by burning the fuel are allowed to disperse in the atmosphere of the room. As long as there is some form of fresh air ventilation in the room, there is generally not a problem with this, as the air will be continuously replenished with fresh air from outside.

Most modern portable containerized gas (generally propane) burning heaters are highly efficient and will burn up to 99% of the fuel cleanly, resulting in very low emissions of harmful gases getting into the room's atmosphere. However, in a very tightly closed off room these gases will accumulate over a period of time and may reach dangerous levels if no action is taken to ventilate the room.

See below in the chapter on observing safety first for an outline of the dangers this may create.

Why Most Heaters Have Venting

vented heatingBut before I get into that, let's ask the obvious question,

"Why do heaters need to be vented?"

Now let's answer that question by explaining how the process that's going on inside the burning chamber works.

When you burn combustible fuels such as gas or propane, wood or other solid fuel such as coal for example, there are several gasses that are produced as a by-product of the combustion process.

Some of these are harmless, but others can be harmful to heath or even toxic.

For that reason, these gases are generally vented to the outside via an exhaust hose, duct or chimney to prevent their build-up inside the home or other building where these fuels are being burned.

That's why homes are built with chimneys to allow the smoke and other gasses to escape into the atmosphere.

But there is also a class of portable heater that also burns combustible fuels that is designed so that it efficiently combusts almost all of the gasses and therefore needs no venting to the outside. However, there are certain limitations to this type of setup, as will be explained below.

Observing Safety First when Using Unvented Heaters

While most new portable propane heaters are very safe in that they convert almost all of the fuel into heat, there is always going to be some small amount of unburned gas that will be given off by the device. The efficiency of the best of these is outlined below:


The flame produced by a modern unit burns with better than 99% efficiency, but not all of that is available as pure heat. Around 9.6% of the energy that is available in gas for heat is derived from the burning of the hydrogen present in the gas. This produces water vapor which must be condensed to recover the heat.

When there is no way to vent this to the outside, that moisture condenses inside the room on any suitable surface. This can cause problems with the creation of molds, wood rot, damp plaster and peeling paint.


The only way to prevent condensation and avoid the problems it creates is to allow it to escape from the room. This is usually done by opening a window or door, which reduces the efficiency of the heater and allows precious warmth from escaping with the moisture.

Noxious Gases

There are several gaseous pollutants that are also released by the combustion process, some of which are harmless while others can be potentially harmful. Of the harmless gases, water vapor and carbon dioxide (CO2) are the most prolific, while the two highly dangerous gases produced are carbon monoxide (CO) and nitrogen dioxide (NO2).

Carbon monoxide (CO) is poisonous if breathed in for prolonged periods and can cause permanent brain and organ damage as well as death. It is undetectable by humans as it is colorless, odorless, tasteless and non-irritating.

In the early stages of poisoning the body, it makes itself known by producing headache, drowsiness and listlessness. If a person exposed to this gas does not seek fresh air, the drowsiness will lead to sleep and eventual death.

Nitrogen Dioxide (NO2) is another toxic gas that can prove highly dangerous if exposure is prolonged. In small does it attacks the upper respiratory system causing irritation, coughing, vertigo, sore throat, headache and nausea.

Preventing Health Hazards of Non-Vented Heaters

The hazards associated with using portable, ventless gas burning heaters can be reduced to acceptable levels by simply providing a means for the dangerous gasses to escape from the room. This is best accomplished by simply cracking open a window and leaving the door ajar to create a cross draft that will carry the harmful gases out of the room while allowing fresh air in.

Doing this will of course cause a slight reduction in temperature, but this is highly preferable to the alternative situation!

It is also important to ensure that your appliance is properly maintained and clean so that it continues working at its peak efficiency, to maintain the cleanest burn and keep dangerous emissions to a minimum. Follow the manufacturer's operating instructions closely and only use an approved model with an ODS pilot.

The Size of Your Home

How large or how small your home happens to be can of course have a bearing on the type and output of any heating devices you choose to use. Larger buildings will require higher output to ensure the larger internal volume is sufficiently warm during the colder weather and often the best course of action is to have a cebtral heating system or HVAC installed for maximum comfort with minimum hassle.

There are of course problems of economy that will crop up when using a central or whole house system as these tend to require a lot of power to run them effectively. Smaller, individual room heating units can be more economical if only those rooms that are actually occupied are heated. Having fixed units installed that are vented through existing chimneys or venting outlets are the norm.

Small homes are of course far more economical to keep warm during cole weather and as long as they are well insulated, you can get away with minimal heating and still be comfortable. For more information on small dwellings, please visit for extensive tips and tricks that make small, beautiful!

Need More Details and Information?

If you need to know more about this type of heating, I have provided several in-depth, information sheets that are published in this website. You can find them by following the page navigation links that are listed at the foot of the page.

I also provide in-depth reviews of the top portable gas heaters that are suitable for use indoors as well as outdoors as supplemental and emergency heating for all situations.

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