Level 19 again - i'm stuck here!!!

[topofsteel]

I got the turret to break the glass to get the cube to climb into the opening that leads to the fan. But that's it!!! Please help.

 

[theholygod]

shoot a portal through the fan

 

[Yogibbear]

me = too slow

 

[Mad-Man]

Take the box and go into the air duct and then go through the fan with a portal on the other side of the fan.