7
1. Safety Precautions
Warning/caution
Caution
Take care with installation site
Air supply
● Air quantity corresponding to that discharged from fume hood must be supplied to the installation site.
If the air quantity is insufficient, the fume hood may not be able to maintain the design discharge air
flow. If so, countermeasures against insufficient air supply may be required.
Crossed air flow (disturbance)
If a fume hood is installed as shown below, crossed air flow (disturbance) is generated. Depending
on the situation, countermeasures against crossed air flow may be required. It is required that the
wind speed of crossed air flow be less than 20 % of wind speed at the front face of fume hood.
● Near the entrance door of the room
Air flow generated by door opening/closing or by entering/exiting of human body exerts an impact on
the hood.
● Human passage
Air flow is generated by a walking person. (The wind speed is estimated as approx. 1.1 m/s, provided
the walking speed is 4 km/h.)
● Near air outlet for air-conditioning/ventilation on the ceiling plane
The blowing wind speed is depending on the shape of outlet, but typically 4 to 6 m/s. As the air goes
away from the outlet, the speed becomes lower, but in some cases, an air flow with significant wind
speed directly comes into the opening of fume hood, or comes into contact with the front face and
then goes down into the opening.
● Near air inlet for air-conditioning/ventilation on the ceiling or on the wall
The suction wind speed at an air inlet is typically 2 to 4 m/s, somewhat smaller than the blowing wind
speed. The extent of disturbance at an inlet is smaller than that at an outlet, because the wind speed
reduces rapidly, as the measuring position goes away from the inlet.
● Front or side face of floorstanding direct blowing package
As the wind speed of direct installing package is high, its air flow sometimes makes a significant effect
on a place which has a long distance from the front face of the package.
In the case of side installation, the side or front air flow from the package may be re-directed by
contacting to an obstacle such as medicine shelf, and the secondary air flow may affect the hood.
● Near ventilation fan
As the wind speed of ventilation fan for suctioning outside air is as fast as typical household electric
fans, a ventilation fan exerts significant effects on the surrounding area.
The suction wind speed of ventilation fan for air discharge is as same as that for air supply. As the
distance between fume hood and fan becomes larger, its speed becomes lower, but depending on
the situation, the fan may affect the hood as a disturbance.
● Open window/door
Crossed air flow may occur due to blow in/out through the window of the room.
