The VAV (Variable Air Volume) system is the most advised system for an intensive and safe use of a fumehood, with a volume variation there is a speed control that no other system guarantees, this means that the user whatever the environment, will always be safe.
The system uses constant velocity readings, as soon as it is low, the sensor sends the information to the central controller, which in turn passes the information to the actuator that adjusts the opening of the damper so that the speed returns to the desired levels.
In addition to the clear and obvious safety benefits of this system, the benefits are also economical. Since the extractions and air volumes are always adapted to the existing needs and there are no unnecessary consumptions, also the room HVAC must be a system with variable air volume, this way, we have an optimization of the consumptions, never having unnecessary consumptions.
Although it is a system that allows for day-to-day savings, it is a much more expensive system to purchase than the CAV, however, the savings in use ends up compensating the user a lot. In case of using a VAV system hood also the room HVAC will have to be thought of as VAV, so that room parameters are fulfilled for your own safety.
As the name implies, the VAV system is a system that varies the volume of air extracted depending on the opening of the window, so we have a stable face velocity, this implies that the safety of the user is guaranteed with the window open or closed. The VAV system comes with a speed reader that makes a constant reading of the extraction values and communicates to the central system which in turn gives information to the actuator that opens or closes the damper a bit, thus controlling the extraction volume and speed facial. This is the most advisable system for a laboratory, since it always guarantees the safety of the user and allows a better saving of energy expenses.
As an extra safety measure, when the window aperture exceeds 500mm or when conditions are not ideal for using the fumehood, the interior light goes from pure white to red, thereby alerting users in a very visible way that the fume hood should not be used under the conditions in which it is at that moment.