"I will. Thank you."
That pretty much means it's time to say goodbye to everything. Not everyone, it might take a while but he'll see them again and anyway he can email them. But the neighborhood is going to be destroyed afterward, and so - if there's the slightest chance he'll wish he could check if that weirdly-shaped rust stain feels like anything if you poke it, or get up on the roof and enjoy being on his roof and not some grey building's roof, he'd better do it while he can.
He makes sure to hug his little sister. He skips down every street and pokes a really questionable fraction of the objects. He sorts his possessions, though at first only by writing up lists. Clothing can be washed, though it's old and will only be older when he gets out; he'll need a mostly new wardrobe anyway. His pocket everything can go to his little sister, though not until he's really actually entirely done using it and ready to touch a new one with clean (!) hands. Part of his aquarium could come with him, in theory - the slightly broken plastic bin that's serving as a tank is smooth and nonporous, almost trivial to clean, and the miscellaneous bits of hard plastic with all their sharp edges filed down that make up the cave are too, and the fake plant went through a really thorough scrubbing before being added to the tank and could probably tolerate that again. But the eggs can't and someone else might want to keep one more generation of annual fish; there's probably time for them to live and die before the district empties. He offers his little sister his stuffed axolotl again but she turns him down (he made it for her when she was a baby but she never did care for it much), so he pets it and informs it that it's very difficult to clean but he's going to do that and will only have to replace the stuffing - "and it won't hurt at all since you're lucky enough to be made of cloth and not actually a moral patient" - and cuts some seams and adds the pieces of the empty cover to the list of things to clean. His shoes can be cleaned. His hairpin can be cleaned. His horrible mattress has really belonged in the trash since it first ended up there and only belongs there more now.
He does still have to keep dyeing his hair red for most of the time he's in decontamination, it doesn't take that long to reach the maximum allowed length of non-red roots. He looks at pictures of short, stereotypically grey haircuts. And yellow, why not, might fit with the accent. He asks Citrus for tips on how to make new friends as a grey. He starts looking for apartments.