Watch This Brave Nanny Save Two Kids As Boiler Explodes

It's a nightmare for so many homeowners when the boiler explodes.

For one family, they had the fright of their life when an explosion happened in their home. The air was dense with debris and alarms went off.

The explosion was caught on the family's nanny cam.

A second nanny cam in another room captured their piano slamming shut from the force of the explosion. The brave nanny ran through the house to save the two kids in her care.

The room that was destroyed in the explosion is the basement playroom where the little ones spend so much of their time.

Still in darkness and surrounded by wreckage, homeowner Chris Reno and his wife, Anna-Maria Faiola spoke to INSIDE EDITION.

They showed us what remains of the basement.

Chris said, “This is the debris, it's all blown apart.”

Damage from flying shrapnel created dark spots on the walls.

Anna-Maria said, “There are nails everywhere.”

The couple's two-year-old daughter, Lily, was actually sleeping in her crib right above the boiler room when it blew.

Anna-Maria said, "If the explosion had gone vertical and that boiler had shot straight up, it would have gone straight into our daughter's room where she was sleeping. So baby Lily would have been very hurt."

So how does something like that happen? Boilers and water heaters can explode when the pressure inside gets too great. One cause is the burner runs continuously, overheating the water and the pressure-relief valve malfunctions.

The Discovery show Mythbusters built a makeshift house to show just how incredibly powerful a water heater explosion can be. In the episode, the water heater is blown right through the floor above and through the roof.

Home-safety expert Ron Hazelton said boiler explosions are very rare. But he gave INSIDE EDITION’s Steven Fabian some useful warning signs everyone should know.

Hazelton said, "You may notice your house unusually hot. You may hear some kind of rumbling sounds which is the water beginning to boil over and gurgle. You may smell like something that kind of smells like hot metal. Now, if all of those conditions are existing, what you should really do is call 911. Call the fire department. Get your family out of the house."

Advice that can help you avoid a nightmare like this family.