You just need a small place sealed with no air that can escape , wether its a room or a tent. The smaller , the better.
Then you let burn enough charcoal outside in open air, a full bag with the notice "burning charcoal inside can kill you" , any of those bags will do it. When there is no smoke coming out of the charcoal, it will be ash grey with red glow , you bring it inside , seal the place you're in and you will die.
You can still do it while its burning with smoke but it will be very bad for your eyes , ive tried a run test.