Share thisA look at the most commonly encountered ventilation schemes for holding rooms intended to be equipped with IVC racks and the decisions to be made in concert by owner and the design professional in order to ensure a successful, reduced-stress project.
In the old days of static cages for rodents, there was no direct connection between the cage racks and the ventilation system. The two could be simply ships passing in the night. Most vivarium designers took the easy way out and designed rodent holding rooms for 15-20 air changes per hour, flushing the room with lots of once through fresh air. This was consistent with the general recommendations in the Guide. Assuming an appropriate scheme had been worked out for supply and exhaust diffusers’ and grilles’ locations, it then didn’t matter which rack and caging system was ultimately purchased (usually directly by the owner) for the holding areas.
This state of affairs has been changing gradually yet dramatically as the trend to provide individually ventilated cages (IVC) on special racks (still usually purchased directly by owner) has gathered steam. Now, with the racks’ air distribution systems designed to be directly tied to a building’s ventilation system (at least for the exhaust air stream), lack of coordination between the two can most certainly result in costly remedial measures having to be performed during the construction phase of the project.
Is it an existing or a new facility?
For obvious reasons, choices for IVC racks and HVAC system selection are more limited in the case of an existing facility. This limitation is usually present, not because the facility lacks the necessary ventilation capacity, but because some aspect of the overall design precludes easy or cost-effective (or both) access to the air distribution system components that would have to be modified.
In a new facility, at least at the outset of the design process, a full range of possibilities exist, and therefore, we will concentrate on this case.
Figure 1 groups the possible ventilation system solutions into several broad categories and subcategories. The three main categories deal with how the air is either delivered or exhausted from any individual IVC rack. The first one looks at possible system configurations when air supply fan modules are added. The second deals with the impact of adding air exhaust fan modules. The third assumes amore direct connection to the building’s ventilation system, where the constant flow volume demands of the racks are met by pressure-independent venturi-type air flow control devices incorporated into the ductwork and air-side HVAC controls.