We meet Mr. Black, a fireman, when he and Stoneman, who like Beatty, are symbols of social orthodoxy, read Montag the five first rules of the Fireman of America:
- Answer the alarm swiftly.
- Start the fire swiftly.
- Burn everything.
- Report back to firehouse immediately.
- Stand alert for other alarms.
The rules emerge as a lie, for the book says they were written by Benjamin Franklin in 1790. Readers of the novel will know this is untrue, even if the men don't. It is also ironic that in a society that uses fireman to enforce a book ban, they have a rulebook.
Later, Mr. Black accompanies Montag, Stoneman, and Beatty to the house of the woman who shocks Montag by immolating herself when they burn her books.
Mrs. Black comes into the picture as Montag sneaks into her house to plant books, part of the plan he and Faber have concocted to sow distrust of firemen and help bring down the book banning regime. He thinks, as he sees her sleeping:
This isn't good, but your husband did it to others and never asked and never wondered and never worried. And now since you're a fireman's wife, it's your house and your turn, for all the houses your husband burned and the people he hurt without thinking.
She is, in other words, yet another symbol of people who mindlessly collude with the system. Having planted the book in her kitchen, he calls in his report of her illegal book ownership and contemplates how she will have to stand shivering outside and watch the roof of her house fall in as the fireman burn it down.
It is ironic that none of this will matter, because the city is soon to be destroyed in a nuclear attack.