Of all the consequences of climate change, heat is the most deadly. Every year, it kills more people around the world than hurricanes, floods or fires. But heat is an invisible threat, a silent criminal whose victims include workers. Millions of workers around the world are exposed to increasingly extreme temperatures. Yet this risk is insufficiently taken into account by many companies and governments. Scientists, doctors, trade unionists and economists are warning of the growing danger that heat poses to the world of work.