Yes especially if that big screen tv is in the fire place, electronics as a whole do not work well when over heated; place a thermometer in the area that you want to mount your flat-screen collect the temperature data, then decide if it's safe to mount you tv. Good luck.
If the heat from your fireplace is being blown forward, then it shouldn't hurt your TV.
no because the heat will affect the electronics in the tv
Generally yes as most of the heat is output from the front of the fireplace, but it is not recommended because any extra heat transferred to the TV can cause overheating. This can ruin your TV set. Therefore its recommended that you place the TV away from a fireplace to avoid damager.
No unless it's excessive heat, but be concerned about dampness!
The primary purpose of a fireback, a metal plate attached to the back of a fireplace, is to hold heat from the fire and reflect the heat back into the room. A secondary purpose of the fireback is to protect the back wall of the fireplace from damage due to repeated exposure to fire.
to prevent heat radiation and damage by people or animals
The fireplace's heat is an example of radiation.
Fireplace
Heat cast forward out of a firepalce is called radiant heat and it the only usable heat that a fireplace can create The wasted heat that a fireplace creates is called combusion heat that rises up the chimney.
A grate heater can be used to make a wood burning fireplace more efficient at heating a home. Fireplaces often use electric fans to blow the heat into the room. Grate heaters use much less electricity than traditional electric fans.
Check and see if your fireplace has heat vents on the sides or above the firebox, and that they are open.
Probably not the smoke, but certainly HEAT would cause problems.