In this quote, the breakfast stove is being personified. Personification is a form of figurative language in which a writer attributes human qualities to something that is not human. Here, Ray Bradbury is saying that the breakfast stove, which is not human, “gave a hissing sigh,” which is an action that a human can do but a stove cannot. The sound that the stove made while it was operating likely sounded like a hissing sigh, but a stove cannot actually sigh as a human being can.
Personification like this makes for rich, dynamic writing. It also helps writers make an impactful point. For example, by assigning human traits to things that are not human, like the breakfast stove and the incinerator, Bradbury is emphasizing the power of technology. He is warning readers that the technology humans have invented is becoming more powerful than humans themselves and showing how this can result in a catastrophe like the nuclear apocalypse.