Horizontal gas and oil-fired steam boilers feature an offset furnace tube wet-back structure, where high-temperature flue gases sequentially wash the second and third return smoke pipes, then exit through the rear smoke chamber and up the chimney into the atmosphere. The boiler is equipped with removable front and rear smoke chamber lids for easy maintenance. It is fitted with an industrial burner of excellent technical performance, incorporating advanced technologies such as automatic proportional combustion adjustment, automatic water regulation, programmed start and stop, and fully automatic operation. It also features automatic protection functions including high and low water level alarms, extremely low water level, over-pressure, and shutdown protection.