From rolls of cardboard to activated charcoal filters – the evolution of the joint filter​ Activated charcoal filters in joints and bongs improve the taste immensely and reduce the contamination of the airways. We at actiTube in Berlin have known this for twenty years and have been applying our knowledge to the development and production of activated charcoal filters for cannabis users since 2001. Before 2001, joints were fitted with cardboard rolls and only the type of cardboard varied. These reduced the temperature of the smoke, but all the harmful substances in the smoke were retained. actiTube was the first company to tackle this uncultivated practice and launched the first activated charcoal filters for joints.