The South Brookline Senior Social will kick off its third year of programs with a cookout from 10:30 a.m. to 1 p.m. Oct. 4 at the Public Library of Brookline’s Putterham Branch, 959 West Roxbury Parkway. The gathering will feature a public-safety presentation by a local police officer, Casey Hatchett, who will offer tips on emergency preparedness. The senior socials will continue from 10:30 a.m. to 1 p.m. on Fridays through Nov. 1 with sessions of gentle chair yoga and tai chi. The town’s Health and Human Services Department, which is sponsoring the yoga sessions, will also be offering free blood-pressure screenings and a presentation about senior nutrition on Nov. 8. Reservations are recommended at least a week in advance for the cookout, as well as the yoga sessions; contact coordinator Regina Frawley at 617-469-0052.