Automatic air vents are used in the closed circuits of solar heating systems. They allow air contained in the fluid to be released automatically during the filling process, through a valve operated by a float in contact with fluid in the system.
The shut-off valves are used in combination with the automatic air vents to isolate them after filling the circuit of solar heating systems.

These series of products have been specially made to work at high temperatures with a glycol medium.

Automatic air vent for solar systems.
Brass body.  Chrome plated.
 
Working temp range:  -20 - 360°F 
Max working pressure:  150 psi
Max discharge pressure:  75 psi

The accumulation of air bubbles in the valve body causes the float to drop so the air vent valve opens. This phenomenon occurs, and consequently, the valve functions correctly, as long as the water pressure remains below the maximum discharge pressure.

Resistance to temperature
The high performance level of this series of automatic air vent valves, required in solar heating systems, is ensured by using materials that are highly resistant to temperature. The materials allow the vent function with glycol water temperatures up to 360ºF (180°C).