Gary's Banter (Verbal Irony)
Throughout the novel, Gary serves as a form of comic relief. He banters and makes jokes, many of which are ironic in nature. For example, shortly after Mark is attacked by the skels in the office building at the beginning of the novel, Gary remarks, "'no one told me it was Casual Friday'" (p. 28). This is an example of verbal irony because Gary obviously knows that it is not "Casual Friday" – in fact, the situation that just occurred was anything but casual. Gary's ironic sense of humor is a prominent feature of his character.
Hope and Survival (Situational Irony)
While many characters in the novel have hopes and dreams about the future, Mark explicitly rejects this way of thinking. As Whitehead writes, "you never heard Mark Spitz say 'When this is all over' or 'Once things get back to normal' or other sentiments of that brand, because he refused them" (p. 32). Instead, he believes "if you weren't concentrating on how to survive the next five minutes, you wouldn't survive them" (p. 32). Ironically, it is Mark's refusal to believe in the future that allows him to survive, and thus to experience that future, while many other characters with ardent hopes for the future end up dying.
Following the Rules After the Apocalypse (Situational Irony)
Despite the fact that society has collapsed and the old way of life has been destroyed, characters in Zone One are still insistent on following rules. For example, the sweepers are only allowed to eat food and wear clothing provided by sponsors who have signed agreements with the government in Buffalo; similarly, when Gary finds a chocolate bar in an abandoned law office, he asks "Are they a sponsor?... we're hungry" (p. 88). Later, when the Omega unit sleeps in a luxurious loft and Gary catches Kaitlyn taking "a dab" of her favorite moisturizer. He chastises her by pulling out "his No-No Cards, brandishing the one depicting a res slash across an open fridge door" (p. 104). It is ironic because the world is in ruins, and the owners of these possessions are most certainly dead, yet the sweepers still insist on following rules about possessions and stealing.
The Victims and the Survivors (Situational Irony)
In a passage near the opening of the novel, the narrator reveals that "those who had been turned into vehicles of the plague" were often those who seemed to live the most successful lives before the plague (p. 31). These people "graduated with admirable GPAs, configured monthly contributions to worthy causes [and] judiciously apportioned their 401(k)s across diverse sectors according to the wisdom of their dead licensed financial advisors" (p. 31). Ironically, the narrator suggests that it was because these people "had been honed and trained so thoroughly by that extinguished world that they were doomed in this one" (p. 31). More ironic still is the fact that it was the people who would have once been deemed unsuccessful–like Gary and Mark–who are able to survive the plague.
