Guide To Flueless Gas Fire Technology

Flueless Gas Fires are a great way to add additional heat and a design feature to your property. There are many myths and rumours surrounding this type of energy efficient gas fire. These are posted mainly on web forums and blogs and while making wild claims the posters never back things up with any real facts regarding the technology, or say how the fires work, the criteria required but most importantly how safe they are. When installed correctly and used the way they are designed to be used, flueless gas fires are a great way to add instant heat to a room.

To cut through all of incorrect information posted on the internet we have created this page to explain the concept of flueless gas fire technology, how the fires are designed to work, the correct installation requirements and the CE testing procedure that must be passed before a manufacturer sell a flueless gas fire in the UK. Then you can make up your own mind.

We would not be able to sell them if they were not safe. Like everything technology moves on and modern flueless gas fires that are sold within the EU are designed to comply with a very strict set of test and manufacturing regulations. This is why there are only a small number of gas fire manufacturers who can sell this style of fireplace in Europe. The modern flueless gas fires have very small levels of emissions - typically around only 3ppm of CO. These emissions are taken using a flue gas analyser directly from the top of the fire. It is a concentrated sample. The emissions are then diluted with the fresh oxygen supplied into the room by the air vent. When you consider a smoker has over 100ppm in their breath you can see how low the emissions are. You will not see that mentioned in blogs or forums! 

What does ppm mean? It means "parts per million parts". During the CE tests this is measured at the outlet of the appliance in a concentrated sample direct from the burner. Once this has been diluted by the oxygen in the room the CO concentration is tiny. You will not see that fact mentioned on the many Forums or Blogs posts that rubbish the technology. This is mainly due to the comments coming from people who have an axe to grind or do not manufacture/sell flueless gas fires and want people to buy something else.

The "Angel Flueless Gas Fire" with a beautiful open flame and no glass screen.

What is the Safety Device? All modern flueless gas fires manufactured and sold in the EU have an ODS pilot system. This special part monitors the oxygen levels in the room. If the air vent is blocked the ODS will shut off the fire long before there is an issue over the emissions. For instance our fire shuts down at only 25ppm, the CE maximum is 80ppm and it is reported that exposure to CO of levels of 800ppm and higher are considered hazardous. Most CO monitors go off at 36ppm to 99ppm when sampling the concentration in the room. This means your cvo flueless gas fire will go switch off "before" the CO alarm goes off. 


What are the main installation requirements?

  1.  A Modern Air Vent. This will allow a trickle of fresh air into the room. A common mistake made is that people think it takes air from the room, it does not. The amount of fresh air supplied into the room by the vent is specified by the gas fire manufacturer and will be shown on the air vent. A modern vent includes baffles which means no drafts. Do not make the mistake of thinking that the manufacturers specified free air is the actual vent size. It is the "amount of fresh air" supplied by the vent and each vent has a different specified amount and high quality vent manufacturer will specify this with the vent. Better still buy the vent from us and you will get a high quality vent with baffles and the correct air supply. If you fit the wrong vent the fire will shut down and appear "unreliable" as the safety device will operate.
  2. A Gas Supply, the gas pressure must be maintained at the manufacturers stated level or the combustion will change.
  3. Room Size, there will be a specified "minimum" room size. The room can be bigger than this, but not smaller. When taking account of the minimum room size it is the height x depth x width in meters - giving a m3 result. Also make an allowance for the amount of furniture in the room.


The flueless gas fires we manufacture have very unique features that other companies do not offer: open flame, no glass or catalytic filters. This means that the air circulating from our fire radiates out from the front and the top. We have manufactured our own unique style of open flame flueless gas fires since 2003. Since then we have won many style and technology awards and the fire has appeared on many TV programs. To date there are many CVO flueless gas fires installed in homes and commercial properties across Europe. At CVO Fire we specialise in manufacturing Flueless Gas Fires with a beautiful open flame.

What are the main reasons to go "Flueless"? Mainly, energy efficiency and there is no need to build or use a chimney. All of the gas you burn is turned to heat and returned to the room. This means you are not wasting money. Despite all the hype in the media, Gas is the cheapest form of utility to use being over 70% cheaper "per kw/h" of heat than wood, electric or bio-ethanol. The reason for buying a secondary heat source for your home is for additional heat. A flueless gas fire will give you between 2.0kw and 3.5kw of heat (depending on your chosen model) and will cost you only 9p to 15p per hour to run. For the same heat an electric fire will cost you 30p to 53p.

 The "Flueless Recess System" this system allows any of our flueless gas fires to be built into the wall.

What makes our flueless gas fires different? They are handmade in the UK using locally sourced materials. Every fire is individually handmade and tested for up to 1 hour before being packed and shipped. Our fire does not need catalytic convertors so also does not need glass on the front, leaving a beautiful open living flame.

What does "Flueless" mean? Flueless means that there is no chimney or flue pipes required to use the fire. All of the emissions from the fire vent from the top or front of the fire. As the fires burn very cleanly a flue or chimney is not required. (Just to be clear - Balanced flue fires need flue pipes up and out of your wall - so they are not flueless - and they cost a lot of money to install.)

How can they be safe, where do the emissions go? Flueless gas fires are very safe. About 20 million are installed in the USA and they can be found in Australia and Japan - two countries with strict environmental laws. The emissions from these appliances are very small. The fire needs an air vent in the room. This vent provides fresh oxygen to replace the oxygen burnt by the fire and keep the air fresh. You should also consider that as a manufacturer our factory is inspected each year by officials from CE to ensure we are making products to the exact standards set our by EU law. Additionally, every month we do our own internal audit on our appliances and we also test the components when they arrive at the factory and before we build the fires. This is what makes our fires the most safe and reliable on the market. The fire also has a safety device. This will shut the fire off if someone tampers with the fire or the air quality is reduced. Our fire shuts down at only 25ppm and it is reported that exposure to CO of levels of 800ppm and higher are considered hazardous.

Is Burning Wood Safer? The emissions from a wood burning appliance are much higher than a flueless gas fire (they can be up to 50x greater). If they are installed with a faulty flue system or the door seal is damaged these emissions will come into the room. Wood burners do not have any ODS system, hence why it is law to have a CO monitor with a wood burner.


Why do I need an Air Vent? The fire burns oxygen from the room to ensure that the flame is clean. As the fire uses a small quantity of the air from within the room this must be replaced by fresh air supplied by the wall vent from outside. If the air vent is the wrong size and does not supply enough air or becomes blocked all together after a period of time the volume of used air will reach a level where the pilot will operate to shut the fire off. This is normally shown by an increase in noise from the pilot. This is why every flueless gas fire has a minimum room size and a minimum specified volume of "free air" that must be supplied in to the room. We supply high quality vents for around £30 that ensure you do not get drafts, it is just a trickle of fresh air. You must never block the vent up otherwise the safety device will operate and shut the fire down.

The "Bonita Traditional Flueless Gas Fire" There are many installation options available with wall mounted, traditional and built in.
See an example of how a Kiah Traditional Fireplace Installation Transformed a Property -


Safety Device Explained. All flueless gas fires sold in the EU have an ODS pilot system. This is a due safety device which will shut off the gas to the main burner if there is a problem. The CE standard says this must operate if the CO in the room reaches a maximum of 80ppm. Our fires shut off at around 25ppm. When you consider a smoker has over 100ppm in their breath you can see how small and sensitive this is. If the fire is installed in a room smaller than the minimum and with the wrong air vent or a blocked vent it will shutdown approx 1 hour or so after being started. This can sometimes lead people to think the fire is faulty however it is indicating an installation fault. Another indication of an installation fault is that the fire stops then later will work perfectly again. Do not use the fire and get a gas engineer to check the complete installation against the manufacturers instructions.

Clean Burning: Flueless Gas Fires have an outstanding safety record because they are designed to burn incredibly cleanly. Most manufacturers use filters or catalytic converters to clean out the emissions however the CVO gas burner technology has taken this a step further and our flueless gas fires burn so clean no filter is required.

Will I get a Stain on the Wall? Without the catalytic convertors and glass screen it means the emissions from our fire are diluted quicker by the fresh air. With other brands of flueless fire the vent on the top of the appliance can concentrate the heat into one fixed outlet area and cause stains on the wall directly above the fire : our fire does not do this.

How do the Running Costs compare with other types of Fires? When replacing a conventional or balanced flue gas fire with a flueless gas fire you will lower your overall gas bills by up to 70%. The annual cost of using a flueless gas fire is around £50/year, compare this to an electric fire of £150/year or burning wood at £500/year for the same heat and you can see why so many people choose flueless gas fires. When considering other appliances, with safety in mind, you should also consider that the emissions from a wood burning fire are very high and these appliances do not have a safety device to shut them down. The dust particles have also been proven to be very hazardous. Wood burning fires may seem glamorous however when considering your family's health great consideration should be put into researching the health hazards of burning wood first.

"We just wanted to drop you a note to say how much we love our open flamed flueless fire.  Its a beautiful looking fire of excellent quality. It warms the room up nicely and everyone we've come across in your company from sales, accounts and delivery have been really helpful and a pleasure to deal with"



Reliability: A CVO Flueless Fireline was installed in a Central London Restaurant in December 2003 and worked continuously until the restaurant was closed in May 2007. This fire operated for typically 15hrs/day, 6 days a week for 41 months = 14,760 hours. This is equivalent to nearly 25 years operating in a domestic property.

History: The Flueless Gas Fire has only recently been introduced in the United Kingdom market, but is one which has been sold in countries such as Australia , Japan , and the USA for many years. Such is the success in these countries that it now outsells conventional chimney appliances.

"If the 15 million Chimney Fires in the UK were replaced by Flueless Fires this would save 40,260,000,000 kW of gas every year and carbon dioxide emissions would reduce by over 7,649,400 tonnes every year. A Flueless Gas Fire converts 100% of the gas to heat where a conventional fire this could be as little as 10%. Running costs are from only 9p per Hour"

Does a Flueless Gas Fire cause Smells in the room? If it is installed correctly, with an air vent in the room, and operated as instructed then NO. As described above the fire uses fresh air from the room. If the air quality is poor then this poor quality air will be drawn into the fire and burned causing a smell. Whenever the cause of smells has been investigated it has not been the fire but by people doing something to the air quality or changes in the home. Examples are: burning scented candles, using air fresheners, decorating, new furniture, spraying aerosols, new carpets etc.

Fuel Efficiency and Economy: The energy efficiency of a Flueless Gas Fire is 100%. This is partly because there is no flue or chimney through which heat can escape and this means that all the heat remains in the room. As a result running costs are very low. This is a considerable saving for the householder. A conventional Chimney or flue set up draws a large amount of air from a house. This means the heat generated by Central Heating systems, when the fire is not in use, is also being lost up the chimney. With a Flueless Fire this situation does not occur.

Can I Install a shelf above a Flueless Fire? Flueless gas fires are designed to be wall mounted. Mounting anything above the fire must be done in line with the CE approval. The fires that we sell are approved with a special deflector which allows a shelf above however this must be done in line with the installation booklet. This deflector must be ordered at the time of ordering the fire. Please ask for details.

Can I Install a Flueless Fire into a wall? Flueless gas fires are designed to be wall mounted however the CVO flueless gas fire is also approved as a recessed version which has allowed customers to install the fire into the wall. Please ask for details.

Flexibility: A flueless gas fire can be used to heat limited use areas or rooms in which some other forms of heating would be difficult or expensive to install such as basements, room extensions and conservatories however there must be a primary heat source also in that room. A flueless gas fire can be installed almost anywhere, even on an inside wall.

Heating your Home: A Flueless Gas Fire works in an opposite way to a conventional gas fire as the heat is distributed gently throughout the property. The vent supplies air into the room which is being heated. This air then circulates in the property giving additional warmth.

Condensation: A myth created by people who do not understand the technology is that a Flueless Gas Fire will cause condensation in your house. This is untrue. Flueless gas fires are a secondary heat source, working with your central heating system. The background air temperature prevents most of the moisture from condensing and it is dispersed by normal air movement.


Consider the Benefits of a CVO Flueless Gas Fire.

There are many Flueless Fires on the market, and you may be considering an alternative, but before you do that, listed below are some of the advantages of buying a CVO Flueless Gas Fires design.

  • Won the Interbuild Energy Efficiency Award 2005 (Fireline)
  • Won the Palmes D'Or Classic Design Award 2006 (Fireline)
  • Have a large and beautiful flame picture.
  • Most models can be set to run on LPG or Natural gas.
  • Burn so cleanly that no filter system is required to clean flue gases.
  • No glass front to obscure the flame.
  • Several  fascia options from Steel to Stone
  • Are handmade in the UK at our factory in County Durham.
  • Are given a 100% full function test before leaving the factory.
  • Are delivered by our staff ( UK Only)
  • Can be recessed into the wall using the optional wall plate.
  • Have Contemporary and Traditional Designs to suit all tastes.
  • [Request Brochure]
  • The Full Flueless Range