Boilers exhaust the air required for combustion, as well as the flue gases, thus do not use the ambient air. One of the two intertwined pipes provides the combustion air, while the other one exhausts the flue gas. This is why there is no problem with regard to indoor ventilation conditions. Upon placing the hermetic gas boiler device on any spot, it must be connected to other spots with air circulation, directly opening up to outside through flue outlets, by using hermetic gas boiler flue extension pipes (see hermetic gas boiler flue equipment section of our website) at technically appropriate lengths. All our products related to hermetic flues have competence and patent certificates