This Halacha is an excerpt from our Sefer
Buy me here or on Amazon.com
May one smoke tobacco/cigarettes?
Tobacco, and many cigarettes contain Chametz ingredients, such as fragrances made from Chametz alcohols, as well as cigarette paper coated with starch. Accordingly, the custom is to be stringent to only smoke cigarettes that have been authorized for use over Pesach. However, from the letter of the law, if the Chametz ingredients that are added are not edible, there is room to be lenient. This may not apply if a Chametz based starch is added to the paper, in which case the starch never loses edibility and would be under Biblical prohibition against eating. The above is only from a Chametz perspective. However, smoking is forbidden throughout the year due to the health risks that it entails.
May one smell snuff/Tobacco?
Yes. It does not require a Hashgacha.
 Admur 467:24 and M”A 467:10 regarding tobacco, that it is commonly soaked in barley and is hence to be put away in a closed room or behind a Mechitza; Sdei Chemed 1:3; See Beis Meir 467; Maharm Shick O.C. 242; Halef Lecha Shlomo 204; Divrei Chaim Y.D. 20; Orchos Chaim [Spinka] 467:21; Kaneh Bosem 1:25
 Admur ibid; Nitei Gavriel Pesach 1; Heard from Harav Eli Landau; See Otzer Minhagei Chabad 23 that the Rebbe Rashab would smoke on Pesach. The students would sift it to make sure that there is no Chametz contained in it.
 One may smoke them being that one does not have intention to eat it, and by inedible items only if one has intention does it become prohibited to eat. [Admur ibid]
 See Beis Meir 467; Maharm Shick O.C. 242; Halef Lecha Shlomo 204; Divrei Chaim Y.D. 20; Orchos Chaim [Spinka] 467:21; Kaneh Bosem 1:25
 The reason: As even if the product contains Chametz, it has been destroyed, and is thus not prohibited in benefit, and smelling is considered benefit and not eating. [Halef Lecha Shlomo] Alternatively, smelling an Issur is considered an irregular form of pleasure which is allowed. [Maharam Shick ibid]