Tried everything to keep air out of hot water system how can you tell if auto vent at the boiler is working and how far do you open the tiny not on the auto vent Thanks Greg

That vent is made by Maid O Mist and is a good one. Read the directions. It says to just loosen the cap no other adjustments are necessary. They should be installed at the highest point in the system to be most effective.

Thanks will give that a try I bleed out the system and about five to ten days later air seems to build up Thanks Greg75

Air can be a problem but hopefully the auto air eliminator will do the trick. Those are the same valves I use on my system. I have a total of 6 of them on the various zones and the entire system will self bleed from a fresh fill in about 5 minutes at the most. Saves a lot of time running around manual bleeding. Make sure your system is tight with no leaks since this will cause air to be introduced with fresh water filling with a automatic fill on the cold water line.