One of the growing trends in home decor is the gas fire, which can come with or without a flue. In general terms, a fire that comes with a flue needs a chimney for the venting of any dangerous gases that build up during combustion.
Conventional gas fires are open-fronted fireplace and inset into a standard sized chimney. The fire draws air from inside your living room to create the flames and the by-product gases escape up the chimney. Of course, these fires look good but they’re not very good for the air quality in your home because the fire is constantly ’stealing’ air to keep on burning.
Flueless gas fires, on the other hand, are, as the name sugggests, designed to work without any flue at all. Generally they use catalytic converters to convert the noxious gases into harmless vapour, which is then allowed into the room.
Balanced flue gas fires use an system allows the products of burning to pass out through the wall directly behind the fire while at the same time drawing in the air needed for combustion via the same route. This type of fire is usually glass fronted and the appliance is completely sealed off from the room.
Power flue gas fires transport combustion products to the outside of the house by means of a fan at the rear of the appliance.
If you want to buy a new fire but are unsure about what type of chimney you have (if any), the quick rule of thumb is that homes built before the late 1960’s tend to have what is 
known as a Class 1 chimney, which is the typical brick built chimney. Homes built after that time could have a Class 2 flue or a Class 2 pre-cast flue. The pictures should help you decide exactly what chimney you have but it is vital that you are certain what type of chimney you have before choosing your gas fire.
