If the neighbours' heating installation is causing you problems, and speaking to them has had no effect, you have to proceed as follows
1) write them a letter with accusé de réception, outlining the problem and asking them to remedy it
2) get a huissier to come and make a constat of the actual nuisance caused to you by their heating installation
3) go to the mairie with all that
(if nothing is done within a reasonable time-frame, you can go for an accelerated procedure in front of the Juge des référés citing article 544 of the code civil demonstrating the abnormal and dangerous nature of the nuisance, since the Mairie has done nothing in spite of its duty to intervene under L 2212.2C of the code général des collectivités)
If you have actual smoke coming into your house, call the pompiers saying there is a fire but you don't know where it is, they will see where it is coming from and a procedure will automatically be put into effect.
There are 68 ramoneurs in Haute Savoie according to the annuaire des ramoneurs français, they must by law issue an insurance certificate when they have done the work, be it on an open fireplace, an insert, a woodburning stove, a boiler etc. You can't however, call in a ramoneur to do somebody else's installation unless they have mandated you to do so, and they will give the certificate to the owner of the installation, not to you, obviously.