I had 2nd and 3rd degree burns to 20% of my body back in 2014 from playing with flash powder, the stuff that gives fireworks their pretty colors. It's basically powdered magnesium and oxidizer. I had to be helicopter lifted to the burn unit. I spent days in ICU and three weeks in hospital. The pain was level 10 for weeks and my body began to shutdown. I had to have skin graft surgery and blood transfusions. I had over 500 staples in my skin from the skin grafts. After getting out of hospital I had to get around with a cane for months as I could barely walk from the pain and skin tightness. I had to go to physical therapy for six months and wear compression garments for a year. I was off work for 3 months and got laid off once I came back. I ended up with drug problems from the pain killers. It completely changed my life. My hospital bill was half a million dollars. It could have been a LOT worse.
Don't mess around with high powered flammables.