is there a chemical that when soaked in paper changes color with the contact of cigarette smoke?
You don’t need to treat a paper with a chemical to show cigarette smoke. A plain white sheet of paper with show it with enough exposure. If you are trying to tell if someone has been smoking somewhere they’re not supposed to, your nose will tell you. If you need evidence for damages in a court, just take a piece of cloth from the place where you suspect that ‘illegal’ smoking has occurred, keep it in a sealed plastic bag and it will be its own witness. I suspect that there’s no litmus paper on the market for this purpose because it’s a less than necessary producct that the public would be willing to pay for.
