Context really is everything.
One of the comments explained this one. I’ll paraphrase:
This is a few years after the Flu epidemic.
Fresh air helped with the Flu.
That means open windows.
But you can’t open windows in the wintertime because it’s too cold.
And being in enclosed spaces meant more transmission of Flu and children would die.
HOWEVER, if you buy their LARGE Radiator, you can LEAVE the windows open if you want AND ALSO heat up the room, preventing children’s deaths.
By saving children from death, this radiator creates life.
Hence: the children coming out of the radiator.