Boiler Safety

I woke up this morning to a loud noise coming from splashing my basement. I opened the door and the basement was filled with steam. I killed the power to the furnace (hot water baseboard heat) and when I went looking there was hot water all over the wall on the side of safety valve. I turned on the camera and saw a steady stream of steam coming from or near the safety valve because it heated back up. What causes hot water to be purged from the system?

Two causes of water out of the safety valve: 1) the valve is defective and 2) the valve did its job (and avoid an explosion ... no kidding).

Your description leads me to say it (2). Looks like you lost water and flash steam boiler.

Not a good situation. Call for an advanced service and does not turn on the system.

This is a potentially life and property threatening problem.

On edit: I will not elaborate on the possible causes lest you be tempted to do yourself a fix, but at least one of your security devices may fail ... cutting of low water.

I can not emphasize enough how potentially dangerous is a steam explosion. The potential for destruction is just as serious as that of a gas leak.

An expansion tank waterlogged.
If you have a bladder type tank, it could be a leak filling the expansion tank and you have no room for expansion to take place.
Press the side of it will tell you if its filled with water.
Safety valve is provided for 30 pounds.
If you need to replace an expansion tank relief they are also cheap and old can continue to run after your done.

sound is a safety valve or bad expansion tank