Zink vaporizes at around 900C or 1600F. If inhaled the vapor can kill you. Galvanized steel is coated in zink and your
RMH can exceed 900C in the heat riser.Welders and blacksmiths have done themselves in. In small doses zink vapor causes flu like symptoms. Attacks get worse with additional exposure. Skin and lung lesions and erratic behavior occur. Some have died with one exposure due to acute resperatory distress.
Wear an asbestos grade mask when welding galvanized pipe.
Avoid galvanized materials in the heat riser. If you do use some galvanized pipe within the system, carefully discard the ashes from the first few firings as the zink settles there. Wear your mask.
Vapors are produced when using angle grinders and cutting wheels.
I went into several blacksmith forums and found that many amateurs were unaware of this risk.
My friend Randy died a few years ago of indeterminate causes. He had all of the symtoms I've read about including some very erratic behavior which resulted in some very cavalier disregard for his health. He couldn't get along with anybody including his young daughter near the end. He would make sweeping accusations etc. So far as I know, heavy metal poisoning was never determined. This all came to light yesterday while I was pursuing safety measures for welding.
He was an amateur welder and blacksmith.