From the Mariners’ press release (via the Seattle Post-Intelligencer):
The two sections … will be cleaned thoroughly before the games and signage will be posted in the surrounding areas alerting fans to the ban on all peanut products in the two sections. There will also be no peanuts or food containing peanut products available at near-by concession stands.
The idea comes from a local father whose son has a severe peanut allergy. The stadium isn’t sure what sort of response it will get but hopes to continue the program, joining a number of teams—both major and minor—that are accommodating fans with nut allergies at their games.