Cigarette smoke contains an amazing array of gaseous and particulate compounds. This includes (in approximate order by mass): carbon dioxide, water, carbon monoxide, particulate matter (mostly tar), nicotine, nitrogen oxides, hydrogen cyanide, ammonia, formaldehyde, phenol and dozens of other well known toxic compounds. Some of these components are present in extremely high concentrations.
For example cigarette smoke contains much higher concentrations of carbon monoxide (0.5-5% v/v) than the auto exhaust from a well maintained vehicle. This concentration of CO would be lethal if inhaled continuously for ~30 minutes.
Acetone, Isoprene, Acetonitrile, pTolualdehyde, Toluene, P,SDimethylhexane, Ethyl Alcohol, Acetaldehyde, Dichloronitromethane, 2,2,4-Trimethyl-l-pentanol, n-Propyl acetate, 2,2-Dimethyl-l-pentanol, Cyclohexane, Hexane, Thiolacetic acid, I-Heptanol, Cyclohexyl alcohol, Benzene, 2-Ethyl-l-hexanone, 2,3,5 Trimethylhexane, Ethyl Imercaptopropionate, Cycloheptatriene, p-Xylene, n-Butyl alcohol, 3,4 Dimethylhexane, Limonene, Isooctyl alcohol, Methyl-n-propyl sulfide, Ethyl-4-methyl-1-pentanol, Neopentyl acetate, Trans4nonenal, n-Heptane, Ethylbenzene, 5-Methyl4heptanone, Dimethylsulfide, P-Methyl-l-pentanol, pl)ichlorobenzene, Trans-3-hexen-l-ol, Capryl alcohol, Mesitylene, n-Hexylmercaptan, 3,4-Dimethylheptane, 2,3,3,4-Tetramethylpentane, 1Chlorohexane, Dichloroacetylene, 2,P-Dimethyl-l-octanol, 2,2,3,3 - Tetramethylhexane, o-Xylene, 2,3,3 - Trimethylhexane, Isopropylalcohol, 2,2-Dimethyl-l-hexanol, 5-Ethyl-l-butanol, Z,P-Dimethylheptane, Furan, Naphthalene, Thiocyclopentane, Cyclopentylalcohol, n-l\lonane, Ethyl phenyl acetate, n-Amyl alcohol, Z,CDimethylheptane, 5-Nitropropane, 2,6 - Di-tert-butyl-4-methyl-phenol, Methyl-tert-butyl-ketone, Di-Tert-butyldisulfide, 2,2-Dimethyl-Shexanone, 1,2-Diethylbenzene, 2,5-Dimethylheptane, 2-Methyl-3-heptanone, Isobutyl alcohol, m-Xylene, 2,2,5,5Tetramethylhexane, n-Decanal, SMethyl-2-butanol, Propiophenone, Ethylacetate, n-Decane, Isopropylbenzene, IEthylpentane, Di-n-Butylamine, N-Dodecane, o-Dichlorobenzene, Allylacetate, S,SDiethylpentane, n-Butyl acetoacetate, Benzylamine, Indene, Methylnaphthalene, 'L-Methyl-Spentanone, Coumarin, Phenylacetic acid, Ethyl valerate, 5-Methyl-3-heptanone, n-Octane, Cumic alcohol, Methanol, 2,4-Dimethyl-Shexanone, Octylacetate, Cycloheptadiene, 2-Methyl-1-octene, Ethyl Lmethylvalerate, o-Nitrotoluene
Too bad they are all part of the normal human exhalation.