First, speak to other occupants in the building to find out what they have done. Second, speak to Management to get their take on the safety and serviceability of the fireplaces. Third, if uncertain about the condition and cleanliness of the chimney, hire a chimney sweep to clean it and while he's doing that ask his opinion. If he's reasonably good and has a trained eye, he can probably tell you a thing or two about it. Given the age of the thing, you might not like what you hear. For instance, you need a new liner because the chimney has aged, and/or you need a new chimney cap. Nothing you can't correct with some money.

thanks haus proud. very good advice. I did speak to the super today, who is going to ask other tenants for names of chimney sweeps they've used.