WHYY By Johann Calhoun, Chalkbeat PhiladelphiaJuly 15, 2021 School District of Philadelphia Chief Operating Officer Reggie McNeil points to the district’s new air and surface purifiers. Thursday’s announcement was made at Juniata Park Academy in the lower Northeast. (Johann Calhoun / Chalkbeat) This story originally appeared on Chalkbeat Philadelphia. Following a contentious year where Philadelphia teachers threatened to strike over ventilation problems in school buildings, Superintendent William Hite announced Thursday that all classrooms will have air and surface purifiers when school starts in the fall. The safety of the city’s aging buildings became a key issue earlier this year in the debate about students returning to school for the first time since March 2020. After the district bought 3,000 window fans to improve air circulation, parents and teachers widely criticized the move on social media. Some even suggested that the fans were dangerous.