When the ambient temperature is high enough, such as during the summer season on Chernarus, a fireplace using sticks or logs will burn at 1,000+ degrees easily causing players nearby to overheat into red and flashing red temperature making being in their vicinity for anything longer than a short period of time impossible due to the damage the player will take. Even when outside, naked or during night the fireplaces can cause this.

So fireplaces do not become ineffective at heating players in cold environments, perhaps a cap on the maximum temperature a fireplace can heat a player could be applied to prevent them being put into critical temperature just by being within a couple of meters of a fire.