The VENT record itself cannot be angled. However, vents can made to
blow at an angle using the SURF parameter VEL_T (listed as Tangential Velocity for Supply surface types).
From the FDS Users Guide, section 9.1.4:
For example, the line
&SURF ID='LOUVER', VEL=-1.2, VEL_T=0.5,-0.3 /
is a boundary condition for a louvered vent that pushes air into the space with a normal velocity of 1.2 m/s and a tangential velocity of 0.5 m/s in either the x or y direction and -0.3 m/s in either the y or z direction, depending on what the normal direction is.
