Steam is input to the bottom face of the block. It has an internal storage of 500 steam. It will light any entity directly above it on fire, consuming 500 steam (its entire storage). It has a 200 tick cooldown period, so even if its steam storage is immediately replenished, it will take 200 ticks until it lights an entity on fire again.
Right clicking on the lock will display a message in chat stating how much steam is currently stored within the Scalding Trap.
It cannot currently be crafted.