Re: Air in the boiler

At about 230 degrees water looses its ability to hold dissolved gasses. Oxygen is what we worry about in the boiler business as it will cause pitting and corrosion. If you leave a means of venting open and wait until the boiler has about 5-10 PSI the water temperature will be high enough to drive off the dissolved oxygen. If you check a steam table steam at 6 PSI is about 230 degrees, this is where the 5-10 PSI comes from. The steam leaving through the vent will carry the oxygen out with it. An oxygen scavanger added to the water will take care of any remaining oxygen, this is often soduim sulfate or hydrazine.