@Margaret843
Hi Margaret, possibly best to be a bit proactive here and leave the guest in no doubt that, if they smoke in the property it will trigger an alarm, and you can use a bit for journalistic licence and make something up like, "As the alarm utilizes WiFi , we get immediate notification if smoking takes place, which is specifically against our house Rules!"
Only a complete moron would want to put that to the test Margaret!
There is widely available a specific cigarette/cigar smoke detector. Here is a good one available through Amazon anywhere in the world.
If triggered it will emit a piercing squeal which will make them wish they had not decided to ignore your smoking policy! You don't have to state in your house rules that it is battery operated :-((
I have ordered one of these to help with my cottage filtration system so, at the moment, I can't tell you how effective it is, but, it does have a 4.5 star rating with Amazon users, and that suggests almost all purchasers are happy with the product!
That price is in $AU Margaret,so it is only going to cost you around $45 US so, I consider it a good investment.
Also if you look on that Amazon site you will see advertised detector/analyzers that are cheap and will give an indication that smoking has taken place.
I will do a post on this at some point in the future when I have had a chance to see it first hand in operation and get to gauge guests reaction to it.
Cheers.......Rob