Firebox design boilers carry with them the tradition of a basic boiler design proven over the last hundred years. A second cousin to the brickset and locomotive steam engine designs of the past, these boilers feature a simple durable construction that provides low maintenance performance year after year.
 

The firebox boiler is typically manufactured to low pressure steam or hot water heating applications often in institutional or light commercial applications. The firebox boiler is a compact, economical unit and serves as a good fit for seasonal use and in applications where high efficiency is not a driving concern.
Firebox design boilers are very similar to scotch firetube boilers in design except they have combustion chambers instead of immersed internal furnace tubes.

These combustion chambers are large crowned combustion zones located at the bottom and center of the boiler. It is because of these large combustion chambers that firebox boilers are still appropriate for the burning of solid fuels. From the combustion chamber are tubes arranged as in a scotch boiler which carry the hot combustion gases through the boiler water on their way to the vent.