Gas boilers are manufactured in thestanding version (standing because Istand on the floor) is a larger watercapacity and power, and in the hangingversion is often designed for installation between cabinets in the kitchen or bathroom. Most manufacturers producegas boilers fired with natural gas andpropane-butane. In the case of liquefiedpetroleum gas is propane-butane tankmounting. They can be divided intoseveral groups: single and double actionwith an open combustion chamber-probably the cheapest and simplest inthe construction of gas boilers, toprovide in the basic version only centralheating-one function or central heatingand hot water – two functions. Boilers, single and double action with a closedcombustion chamber “Turbo”-like theprevious version with one function onlyprovide central heating-with two-wellhot water but with a closed combustionchamber does not draw combustion airfrom the room in which they areinstalled. This is important in a situationwhere there is no dedicated a special boiler room and the unit must be placedin the kitchen or bathroom. Higher costthan its predecessor but more comfortand security. Condensing boilers anddouble action-in functions similar topredecessors but in the construction ofmore complicated, with a closedcombustion chamber, can under certainconditions-regenerative heat from theexhaust, which in the case of classic boilers rise to the chimney. Comfortableand safe but much more expensive thanpredecessors.