Ringelmann scale. A evaluate of smoke coloration. Invented by Professor Maximilian Ringelmann in Paris in 1888, it is actually a card with squares of black, white and shades of gray and that is held up as well as the comparative grayness of your smoke judged. Electrostatic precipitation. The smoke https://broadfar.com/oraco-pioneering-a-smokeless-future-with-innovative-nicotine-delivery/