Does anyone use air alert monitors in the units or anything that is able to detect cigarette smoke? 

I've seen a gun, smelt weed and seen cigarette ash and an unmentioned pet in all but one of my rentals.

It is legal to have a pet and it is legal to smoke cigarettes.

Such as smoking and leaving a cigarette out which burns the house or some unfortunate accident.

There is a lot of damage however.There is a large number of cigarette burns in the carpet and there are many stains on the carpet throughout the unit.

I walked the property today and found several cigarette butts. 

Appliances at per hour rate Window cleaning, tracks, at per window rate, A/C filter cleaning / wash it 10.00Bath tub at hourly rate Key replacement, lock replacement, mail box key, remote control.Glass and screen repair as per item Carpet Cleaning extra spot removal, cigarette burns, pet odor Sheetrock repair, nail holes starting at 15.00 per roomNicotine smoke or grease smoked walls, wall wash, kilz primer per room charge, extra for ceilings.Any furniture left per item, list couch 45.00, chair 25.00, mattress 25.00  plus labor to move.

That yard is now a private paradise, a place where we can relax, grow garlic, and cultivate our spice garden, or at least it still would be if it wasn’t for the sound of my new neighbors’ barking dogs in the night, their cars left running even in warm weather until the exhaust fills my carport 10 feet away, the metallic clink of trucks be fixed in their carport at 10 pm and later, and the pungent smell of cigarette smoke that floats over the 3-foot tall wall separating our yards and into my front door.Unfortunately the 2005 real estate bubble trouble and the 2007-2008 subprime mortgage debacle changed our neighborhood by filling it with rental homes, many sold at auction for ridiculously low prices, and now owned by absentee landlords instead of owner occupants or local landlords.

And for the love of someone... take your coke/coffee cups with you when you go... especially the ones with tobacco spit and cigarette butts in them...

Unless you want to have a place that's hard to rent you should have a no smoking policy, pot or cigarettes or pipes or cigars or anything else.