The face velocity of lab fume hood

There are different types of fume hoods in laboratory. The wind volume and wind speed for every type of fume hood should reach strict regulation, do you know the face velocity of fume hood?
The regular face velocity for fume hood is 0.5m/s. Also the face velocity depends on different test status, different area and different altitude.
For example, if the gas density is big during experiment, it means that face velocity should be a little higher, or the waste air can’t be discharged on time.
In different area we need to select different fume hoods as per local climate. So the standard of face velocity isn’t same in different countries.