I have a ventless gas fireplace which recently had a change in flame color. When first lit, areas that were normally all blue, were blue with yellow flickers. I was told this was ok. But about 8 hours later, I noticed the flames had all connected and had a blue outline. There was also a sewer-like smell in the room. I immediately turned the fireplace off and closed the gas line. What I want to know is, is what did this change in color and appearance mean? I'm terrified to turn it back on, but I'm also freezing.