 An Engineer Guy video on YouTube where discusses the invention of the industrial cigarette rolling machine indirectly answer that question. <a href="https:&#x2F;&#x2F;youtu.be&#x2F;_4zbNJmtbGo?t=51" rel="nofollow">https:&#x2F;&#x2F;youtu.be&#x2F;_4zbNJmtbGo?t=51</a><p>The short version is cigarette smoke is inhaled pipe and cigar more or less just in the mouth. The nicotine in the smoke in the lungs is rapidly absorbed into the blood which goes to the brain in seconds.