Years ago I visited an old friend and when I went into his bedroom, I saw his gas space heater was putting out an all yellow flame. The ceiling and walls down to about 2 feet off the floor were totally covered in soot. There were carbon balls on the ceramic radiants of the heater and all over the floor underneath. So I adjusted it for him. He admitted that he woke up every morning with a splitting headache. Its a wonder he even woke up at all.