Steam from a low pressure vessel 2

[DDoreee]

Hello,
I have a vessel with steam and water at around 0.5 bar. When I open the valve between the top of this container and the exterior that is air at atmospheric pressure I see a lot of steam coming out. I was expecting the air to fill the vessel, so why is the steam streaming out if it’s at a lower pressure?

 

[DDoreee]

So I don’t have special equipment like high speed camera, but I think it’s just the air circulating really quickly, like speculated before. Thank you for you answers.