I don't have them yet but I'll soon be putting in smart smoke/carbon monoxide detectors too.  

I had a terrible appraiser who failed to see the carbon monoxide tester in the home, failed to ask the home owner (who was right there) about it, and then I was charged for the second visit.

My uncle built his own house in Glen Carbon Illinois about 10 years ago. 

I've been reading a bit and cannot get a good answer in IF the landlord is required to supply/maintain CM detectors.  And how many should a house have???   Thanks for the help!!! 

I've had them discover a furnace that was pumpin out too much carbon monoxide.

While increasing your property value, reducing carbon foot print, increasing cashflow, and make the rental property more appealing to high end consumers.It seems like a pretty solid plan to me, and I plan on implementing it when I get some rentals, can any landlords give me their opinions on this?

It's also the right thing to do- each of these bulbs reduces carbon dioxide emissions dramatically versus the incandescent bulb, and also significantly versus the CFL.

(doing it from memory but it was something like 2x's for conventional resistance heating vs electric)As long as the furnace is properly vented (ie no birds or rodents have climbed into the stack, I would stick with natural gas.)Contrary to the isolated incidents that hit the news, natural gas is very safe, and carbon monoxide poisoning from a natural gas furnace is almost non existent. 

Also make sure you have working carbon monoxide detectors.  

Do monthly or quarterly cleaning inspections (which includes checking smoke/carbon and fire extinguishers).