normal circumstances, factors that affect the fume hood airflow control
objectives include: fume hood structure, surface wind speed,
turbulence, response time, the minimum air volume. And in response to
the management goal and the possibility of unexpected circumstances, the
specification is usually for on-site monitoring, emergency operation,
etc, also have more specific specification requirements.
Fume hood structure
its ventilation cabinet structure design is reasonable, any two points
of the fume hood surface wind speed deviation less than or equal to 15%,
the overall structure resistance less than 70 pa. And in accordance
with the relevant EN or ASHRAE standard fume hood need through a series
of strict test before they go out.
Ventilation counter wind speed
Into the fume hood airflow through the operation of the fume hood face velocity, called ventilation counter wind speed.
surface wind speed is reaction hood inhibition effect is one of the
important parameters, many countries have clear standards requirements.
Normally, asked someone before fume hood operation, due to its body in
front of the fume hood will form a vacuum airflow, therefore, surface
wind speed requirements control in 0.5 m/s, when no operator before the
fume hood, can be appropriate to reduce the surface wind speed 0.3 m/s.
German DIN standard, due to its requirement for the fume hood structure
is different from other national standards, so the surface wind speed
standard requirement is lower than the rest of the world.