A boiler explosion is a catastrophic failure of a boiler. As seen today, boiler explosions are of two kinds. One kind is a failure of the pressure parts of the steam and water sides.
There can be many different causes, such as failure of the safety valve, corrosion of critical parts of the boiler, or low water level.
Corrosion along the edges of lap joints was a common cause of early boiler explosions. The second kind is a fuel/air explosion in the furnace, which would more properly be termed a firebox explosion.
Firebox explosions in solid-fuel-fired boilers are rare, but firebox explosions in gas or oil-fired boilers are still a potential hazard.Źródło: https://en.wikipedia.org/wiki/Boiler_explosion
After its installation, the current home plumber, could also make his first start and check thanks to proper operation.
A boiler that has a loss of feed water and is permitted to boil dry can be extremely dangerous.
The Hartford Loop was invented in 1919 by the Hartford Steam Boiler and Insurance Company as a method to help prevent this condition from occurring, and thereby reduce their insurance claimsŹródło: https://en.wikipedia.org/wiki/Boiler#Safety.