Pharos produces professional gas forges for commercial use, this one is a few years old, but works great. I was thinking about building a gas forge myself like most others, but these have usually burners which are oversized soldering irons. As a result, these forges are not particularly efficient. The system that Pharos uses, uses blowers to supply oxygen and thus requires much less gas and the gas pressure only is 30 millibar. There are also various safety devices and the risk of CO formation is almost eliminated by the forced ventilation and the mixture monitor.
The knife which we then forge consists of the outer ring of a ball bearing which was replaced during the restoration of one of our locomotives. The steel is very difficult to machine but has excellent properties as a knife steel. According to my research, it is 51100. Since soft annealing, stress relieving, hardening and tempering worked extremely well, it should actually be 51100.