Heating System component question - what is this?

[mike2016]

Hi,

What is this in relation to my heating system? I've a gas boiler but wondered where the air vents out if needed. There is one in the boiler, you have the radiator bleed vents but then what is this used for? 

Thanks! 

[ProDave]

Automatic air bleed valve.  Unscrew the little cap on the top and any air that has accumulated will hiss out.

[Conor]

Before you do this, make sure you know where the valves are to isolate the heating pipe loop. Last thing you want to do is have a failure and uncontrolled release of water. Reccomedation from personal experience.

[Radian]

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