Hello default...smile. H2S or hydrogen sulphide is produced when an acid and lime sulphur are mixed together. There is quite a bit of information on the procedure in the resource section on SS. The sulphur dip must have at least 40% of the sulphur in order for this to work, and you must be very careful to get the right amount. Much like CO, (carbon monoxide) you must wait for the levels to rise for the 'knock down effect' to take place. In a sealed car that requires 4-6 minutes. That is the time you must sit there in a highly acidic atmosphere: air that burns lungs, eyes, nose, mouth, etc. Not a happy place to be. There have been reports of people removing the handles from car doors so that they cannot get out of the car in time. I highly recommend that you look into this method a little more.