A constant air volume for the intended safety level
CAV Extraction System
A system that uses a speed and volume of constant extraction, which makes it necessary in the case of the fume hoods to resort to bypass so that there is no variation of the velocity to the face of the fume hood less than 0,3m / s or greater than 0,5m/s . The Bypass allows the user to open and close the window without varying the speed and staying within the safety standards.
This system presents a reasonable level of safety but at economic levels becomes very expensive, as it makes extraction volumes which may be unnecessary if the window of the fumehood is closed, and a higher extraction volume means a higher volume of insufflation, all this is then converted into energy consumption which in this type of system can be high.
As this extraction system presents constant air volumes, the HVAC system of the room where it is being inserted can be also simple, since to maintain the temperature and the atmospheric pressure within the parameters does not need to make great adjustments to what is normalized.
The CAV / VAC (Constant Air Volume) system is a constant air extraction system, where the volume of air extracted by the fume hood is always constant regardless of the window opening. With the variation of the height of the window, the velocity of the passage of air varies, for example, from 500mm the facial velocity is from 0.3 to 0.5 m/s, when closing the window the velocity increases, creating turbulence and noise.
It is the most basic system, the least expensive to acquire and the most expensive to operate.
Industrial Laborum has two types of controllers, the simple controller, which has only two buttons: one to turn the ventilation on/off and another to turn the luminaire on/off. The second controller, CAV, which has a button to turn on/off the ventilation, another button to turn on/off the luminaire, has a screen that allows the visualization of the speed of air passage. This second one features an audible alarm for air extraction failure. Both controllers will be implemented and fixed outside the fume hood, in one of the towers or in the service panels below the work surface.
The CAV system is the cheapest at the time of purchase, but in the long run it becomes the most expensive. Since this does not adapt to the opening of the window, the air volume will have to be calculated for the maximum opening, this implies a high volume of extracted air. Thus, the volume of replacement air in the room will be high, as well as the temperature and pressure control in the room will have much higher costs compared to other systems.
The extraction carried out by the fume hoods with CAV system is an extraction that does not necessarily imply an HVAC in the room, it is also governed by a CAV system, however, an HVAC with VAV system is the most recommended, since the control of the area where the hoods are inserted be as accurate as possible. This also makes it possible for the user to use only a hood without a sudden rise in temperature or an increase in pressure, which could put the user in danger.
All these variants later turn into high laboratory maintenance cost. It can be summarized that the CAV system is not the most suitable for large laboratories, and that despite being cheaper in the short term, in the long term it is the most expensive.
Of all traditional extraction systems, the most recommended is the VAV system. A system that performs constant speed measurements inside the fume hood, thus being able to adapt the extracted air volume. This adaptation of the system to the conditions allows for substantial energy savings and user safety to be improved, despite being a more expensive system than the CAV.
With a VAV extraction system, it is recommended that the laboratory's HVAC be also a VAV system, since this way the accuracy of pressure, temperature and all environmental parameters in the room are guaranteed and remain so.
The end result of this initial investment, (systems with a higher price), is that user safety is improved and the maintenance cost of the fume hoods in use is much lower compared to the CAV system. This is the recommended system for large laboratories and for areas where atmospheric pressure and temperature control will have to be precise.
We are available to get in touch with you, as we also develop solutions for areas other than those mentioned above.
Industrial Laborum Ibérica is a company with 44 years of experience in the market, which seeks to bring the quality factor to all laboratories. Through customers in the most diverse areas, such as health, education and different industries, ILI has acquired know-how that allows it to create solutions for the needs or requests of its customers. We are here to develop labs for people.