The black that people are getting on their snow is from their butane lighters it is a fossil fuel that is not burning properly and leaving soot behind. The videos I saw with the snow turning black the person was holding their lighter on the side or even slightly under it so the fumes and soot where being captured by the snow, in your demonstration your flame was basically on the top of the snow so your exhaust was venting into the air. The order you were smelling was most likely coming from you lighter becoming hot from prolonged use. The lack of water was because the loosely packed snow absorbed the water, snow will practically turn to slush, only then will it be totally saturated then it will release the water. I did a similar experiment using a torch fueled with MAP gas. It the residual water pure? Most likely not, due to the petroleum absorbed from the heating process, and the many industrial chemicals polluting our atmosphere, plus whatever else the govt. may be dumping in on us.