The low-pressure boiler seen above is used for heating household water by burning solid fuels, e.g., wood, hard coal or brown coal. The upper part of the boiler consists of an enclosed vessel made of copper sheets operating on the overflow principle, and an internal pipe for discharging hot gases from the burner at the bottom of the boiler. This invention significantly improved the standards of household hygiene by providing access to domestic hot water. It was very widely used in residential buildings from the mid-19th century, i.e. from the time when the modern water supply system was invented, up until the 1960s. Operation of the boiler required the user to abide by basic safety principles as there was a very high risk of carbon monoxide poisoning (which could take place if the water exceeded the critical temperature in the tank), much higher than in the case of the later gas-fired boilers. The next stage in the development of the device was the gas fired boiler, which was patented in 1894 by Johannes Vaillant and took advantage of the growing gas networks in cities. The main improvement in comparison to the solid fuel-fired boilers was that it was no longer necessary to add fuel to the furnace or to remove the ashes. The device presented was removed from an apartment in a tenement house in Studencka street in Kraków.
Interesting fact: boilers of similar design and function as the one presented here are still manufactured for use in places without access to gas or electricity.

References:
F. M. Steingress, Low Pressure Boilers, issue IV, Orland Park 2001.