Why does popcorn contain lead

No lead, the old-fashioned popcorn machine and old-fashioned pressure cooker are civilian pressure vessels, according to regulations will have overpressure melting fuse, the fuse in the temperature and pressure exceeds the limit will be quickly melted to the pressure relief, so as not to explode. Processing food due to high temperature fuse will always have a small amount of sublimation into a gaseous condensation on the food, so the old machine will have a trace of lead processing out. Nowadays, the fuse does not contain lead, so high-pressure lead processed food and popcorn do not have this problem.