Parallel controls use separate motors to regulate fuel flow and airflow, enabling each motor to be tuned throughout the boiler ignition range. During installation, to points are usually drawn to create a curve of airflow corresponding to the fuel flow. The air-fuel ratio can be varied along the ignition range to prepare the optimal ratio in different ignition conditions. Also with the use of electronic dampers, this method of control is very reproducible.

To increase the overall efficiency of the boiler, the heat released from the combustion process must be properly transferred into the fluid used. Any heat that is not transferred to the fluid is lost through the body of the boiler or the flue gas. The temperature of the gas inside the chimney is a good indicator of the heat transfer process and therefore efficiency. There are practical limitations to the low flue temperature. Its temperature will be higher than the fluid used in the boiler. In boilers that do not do distillation, the temperature should be high enough that water vapor does not distill in the exhaust chimney and clean the heat transfer surface in the distillation that causes corrosion. Condensing boilers that use natural gas are made and designed with accessories that are resistant to corrosion. Also, their chimney temperature can be less than . degrees Celsius. Trapping heat distillation increases efficiency by more than %.

All combustion equipment must be operated properly to prevent hazardous conditions, catastrophic damage, and human and construction damage. The main reason for the explosion of engine room boilers is the combustion of flammable gases that have accumulated inside the engine room boilers. This can happen for a variety of reasons, such as fuel, air, or the combustion process is interrupted for any reason, the flame goes out, and flammable gases accumulate that cause re-burning.

Older hot water boilers operate without distilling water vapor from the gas vent. This prevents corrosion and component breakdown. The return temperature of the distillation boilers during operation is lower than that of the old boilers, which distills the water vapor coming out of the ventilator. This enables the condensing boiler to extract excess heat from the water vapor phase to the extraction liquid and increase the boiler efficiency. Some carbon dioxide dissolves in the distillation to form carbonic acid. While some condensing boilers are designed to control distillation that causes corrosion, other engine room boilers require equipment to neutralize distillation. Traditional engine room boilers that do not perform distillation operations mainly operate in the range of % -% combustion efficiency and distillation boilers operate in the range of % -% combustion efficiency.

Steel boilers, as their name implies, are made of steel and are usually made of horizontal cylinders. Steel boilers have a combustion chamber in which pipes are placed around this chamber. The pipes that are installed around the combustion chamber of steel boilers are made of a special alloy so that they do not burn or damage in the face of a direct flame. These pipes are called (fire pipes). Steel boilers are divided into friends from the point of view of heat transfer, which are as follows.