Seven people received medical attention on Tuesday after an iPhone battery overheated in a Swiss Apple store. Police in Zurich, Switzerland evacuated around 50 customers and staff from the store after an iPhone 6S battery overheated and started spewing smoke. The small fire happened as an employee tried to repair the device. The man was treated for minor burns to his hand. Lithium ion batteries, used by most smartphones, are notoriously flammable, even though fires are mercifully uncommon.