I would suggest contacting a licensed chimney sweep. A fireplace system should be inspected annually by a chimney sweep. I Googled the Chimney Safety Institute, and they are now on Facebook, or they can be found at http://www.csia.org/ NFPA The National Fire Protection Association is also on FB now.
I have personally known an authentic Chimney Sweep for over 30 years, sitting for hours listening to customers talk about their problems, and solutions.
A Chimney Sweep must be tested every few years to retain their standing, because Insurance companies give discounts to homeowners who use a Chimney Sweep each year.
Considering your family is at stake, an inspection is usually under $100.00, and again, you get a rebate from your insurance company, and possibly a reduction in rates for using a Chimney Sweep, my final answer is; make an appointment for a member of the Chimney Sweep guild to inspect your system, and make recommendations and/or modifications which could be life saving.