Fireplaces, Heating Stoves, Flues and Chimneys - Can chimney be painted?

We are converting the second floor of our home and have the chimney running through the middle of the area we are converting. We have a boiler in the basement venting (?) through this chimney (I'm not sure that's the proper wording, but in any event the boiler goes into this chimney). I'm curious as to whether the chimney can be sealed/painted on this second floor? I didn't know if this was safe or if there was a special type of sealer/paint that had to be used...

We don't want to wall the chimney in at the moment as we recently had the roof torn off/new roof put on and want to check over this winter to make sure nothing is leaking around chimney/vent pipe.

Thanks for your time! Sorry if someone already asked this question. I found the search engine a bit confusing...

Since you did not say, I am assuming that you are referring to a brick chimney. If so, it probably has a liner running up through it. Check this though. If the brick does not get really warm when the boiler is running, I see no problem with painting it. Glad to see you are checking the roof job for leaks before covering up a potntial mess. Good luck.