It all depends on what your smoking and how often and if your indoors or out .. An occasional joint or bowl will do no harm but tobacco smoking around gardens in general is not advised as noted due to Mosaic Virus . Smoking indoors creates second hand smoke as we all know , this has also been proven to leave chemical residues upon its contact , why allow this in your grow and on your plants . In time it will clog the plants stomata as well as your filtration system and as well the film from the smoke will collect on lamps and bulbs . No win situation and its best to go outside and smoke . Now I do admit to smoking some bud now and then while working in the grow , its just second nature and usually happens to be in my hand when I enter my grow .