Fires can be lethal if not serviced regularly, they come in various types such as inset, outset, hole in the wall, ect.
Yellowing/orange flames indicate a potential danger, flues are inspected during any work carried out on the fire.
If you want to change your fire I would always recommend a survey is carried out by a by myself who is a registered engineer, to check and certify the compatibility of your chimney, hearth and mantel piece, flue or circumstances.
Gas Safe Register
The Gas Safe Register replaced Corgi as the official resgistrar of approved gas fire installers.
Always use a fully qualified Gas Safe registered engineer