"We had just walked into the fentanyl lab when the cook poured a white powder into a stockpot full of liquid."

"He began mixing it with an immersion blender and fumes rose from the pot, filling the small kitchen. We wore gas masks and hazmat suits, but the cook had on only a surgical mask. He and his partner had rushed here to fulfill an order for 10 kilograms of fentanyl. While one sniff of the toxic chemicals could kill us, they explained, they had built up a tolerance to the lethal drug. But then, the cook jerked back. 'It really hit me,' he said, looking dazed. 'I need to take a breather.'"

From "'This Is What Makes Us Rich': Inside a Sinaloa Cartel Fentanyl Lab/New York Times reporters witnessed the dangerous fentanyl production process inside a secret lab in Culiacán run by Mexico’s most powerful criminal syndicate" (NYT)(free-access link, so you can see interesting photographs of appalling stovetop cookery).