A vivarium primer: Keys to planning for success By Sean P. Cuddahy, AIA, LEED AP, and Erik W. Terry, LEED AP Three components generally determine how well an animal facility will function: animal caging, the configuration of the room, and personnel and material flow in and out of the facility. This article explores these three areas in order to align the design of a facility with vivarium protocols and practices. Identifying and selecting the best solutions early can help to avoid disruptive and costly changes in the future. For any project, new construction or renovation, strategies should be determined by what is most effective for that particular facility—taking into consideration the specific details of staffing resources and budget. The planning process should always work toward answering three basic questions: • What works now? • What could work better? • What design will retain what is currently working, improve what is not, and satisfy future requirements? Animal caging All animals in a vivarium are contained in some type of caging system within a holding room; the design of the caging system should be carefully considered. The choice of animal caging also affects personnel in the amount of exposure to ambient animal allergens and the ergonomics of performing frequent bedding changes. Efficiency, safety, and flexibility are also important, as well as animal husbandry within the holding room. An in-depth comparison of three caging systems will help illustrate these issues: • Static micro-isolator caging This system consists of a series of cages constructed of high-impact, chemically resistant polycarbonate plastic with filtered tops that are placed on mobile racks. The cages are dependent on the natural air circulation from the room to provide adequate air exchange rates for the animals. This is considered a “static” system of caging, because no air is mechanically delivered or removed from the units. The micro-isolators come in different sizes to accommodate different species of small animals such as mice and rats. At the bottom of each cage is disposable bedding material that must be periodically changed by the husbandry staff. Each micro-isolator may be handled without breaking the cage-level microbiological barrier. When required, the cages can be opened in a laminar flow workbench to do bedding changes and animal manipulations without breaking the microbiological barrier from cage to cage. Although air exchange rates in static micro- isolators may be adequate, ammonia, carbon dioxide, and humidity cannot be regulated. The build-up of ammonia drives the number of cage changes required. With this type of system, bedding for each micro-isolator typically must be changed twice a week. Fig. 1. Common configurations for ventilated cage racks. All diagrams: CUH2A. Click to enlarge.   The cages and the racks are reusable after they have been sterilized, but it should be noted that the lifespan of the average polycarbonate cage is only about two years. The lifespan of the polycarbonate cages is further reduced in biohazard areas, where it is required that all material leaving the biohazard area must be put through an autoclave. This means that all the cages must be replaced every two years at the longest. • Ventilated caging This system, like the previous one, also consists of a series of cages constructed of high-impact, chemically resistant polycarbonate plastic with filter tops that are placed into ventilated mobile racks. Like the static micro-isolator caging, the ventilated caging system is also designed to house small animals such as mice and rats. The significant difference between this system of caging and the static micro-isolator system is that low-velocity HEPA-filtered air is mechanically delivered to each cage and exhausted. This assures barrier protection for laboratory animals and personnel as well as sustained regulation of airborne particulates, ammonia, carbon dioxide, and humidity levels. Ventilated racks come in a variety of configurations that can be grouped into three broad categories (Fig. 1, above). Each has advantages and disadvantages. Racks that recirculate room air come equipped with individual HEPA-filtered supply and exhaust blowers mounted on each rack. They have greater flexibility and operational visibility than those that are tied into a building air system, but there is an increased heat load to the room as well as increased noise levels and odor. Racks that are directly connected to a dedicated building supply and exhaust air system have superior odor, heat, and noise reduction compared with recirculating racks. The disadvantage of this approach lies in total dependence on the building air system to maintain the proper static pressure and achieve proper air balancing at the rack. Redundancy in the rack ventilation system is also totally dependent on what is provided by the building system, so this can be quite costly. There is also less flexibility, as it is very difficult to convert rooms to other species when the racks in that room are connected to a building system that is dedicated to a particular species. Racks that are tied to a building air system through thimble connections are a hybrid of the two options described above. Each rack comes equipped with individual HEPA-filtered supply and exhaust blowers mounted on top. The supply blower draws the air from the room and delivers it to the individual cages. The exhaust blower connects to a dedicated building exhaust air system through a thimble unit located directly above it. This type of configuration allows racks to operate using the building air system, with static pressure and air balancing being regulated locally at the blowers. The connection to a dedicated building exhaust system facilitates removal of odor and heat from the room. Should the building air system go down temporarily, the exhaust blowers can continue to operate—venting into the room through the thimble connection. Ventilated racks offer another major opportunity over conventional static micro-isolator racks. They allow for a higher density of cages, increasing the capacity of animals that can be housed in each rack. A 20 to 40% increase in animal capacity is possible with no additional increase in square footage. This potentially reduces the amount of space that needs to be dedicated for animal housing, freeing it up for other functions or reducing the overall square footage of the facility. It should be noted however that if the animal population increases, so does the number of personnel responsible for caring for that population. High-density caging also has a higher first cost, but this can be offset by the construction cost savings associated with a reduction in square footage.   For use in biohazard areas, vendors offer ventilated rack systems that are specially designed for containment. These models provide a lower density of cages that does not allow an increase in animal capacity through the rack system. Numerous studies have identified ventilated caging systems as a primary means of reducing ambient animal allergens, thereby reducing cost increases in animal care and personnel. And because bedding changes need to be performed less frequently—sometimes as little as every two weeks—ventilated caging systems also reduce repetitive stress injury. It has been reported that using ventilated cages, as opposed to static cages, can reduce the direct personnel labor costs by as much as 40 to 60%, resulting in a 20 to 30% savings in husbandry costs. • Disposable caging This system consists of a series of fully disposable or recyclable cages constructed of PET recyclable plastic that are docked on mobile ventilated racks. It should be noted that there are several limitations to this system: it is a new technology, it is currently designed only to house mice, and it is available from only one manufacturer (Innovive Inc. of San Diego).   Disposable caging improves animal housing capacity by recapturing cage-wash area and storage space. It eliminates repetitive stress injuries associated with cage cleaning and sterilization. The cages are lightweight and easy to handle, as are the racks—facilitating transportation and maintenance. The rack system comes at a significantly reduced first cost and operating cost. Also, the reduced stress on throughput infrastructure saves on capital expenditures for rack washers, tunnel washers, autoclaves, automation, and robotics, as well as utility costs. Room configuration Much of the real estate that makes up a vivarium consists of animal holding rooms and their associated procedure rooms. A major driver that determines the size and arrangement of these rooms is the species that must be accommodated. This influences not only the equipment that is to be in that room, but also the activities of the husbandry and scientific staff. Therefore, the need to design rooms to house a single species vs. multiple species has a significant impact on the flexibility and square footage of the overall facility. Activities within animal holding rooms or adjacent procedure rooms can be divided into husbandry or science. Since both husbandry and science need to occur in these rooms, it is important that the two groups are able to function without bumping into each other. The objective of husbandry is to care for the animals in the room and maintain the sanitary conditions required for the scientific investigation that needs to occur there. There are several factors that need to be considered to facilitate the activities of the husbandry staff: • Easy access to the racks for handling of the animals and cage changing. • Lighting levels that allow for examination of the animals’ health. • Ergonomics that avoid repetitive stress injuries. • Straight access into the rooms with a clear aisle to allow for easy movement of equipment and racks into and out of the room. • Protection of staff from exposure to ambient animal allergens. • Finishes that permit easy sanitization of the room surfaces. • Mobility of the equipment and caging for easy removal and cleaning. Scientific activities may occur in the holding rooms or in the adjacent procedure rooms. The scientific staff has different operational needs from those of the husbandry staff: • Easy access to the racks for observation and handling of the animals to do procedures. • Lighting levels that allow for observation of the animals. • Biosurety that prevents cross-contamination between animal subjects. • An environment for the animals that is constant and controlled during studies. Biosafety is also a driver for room configurations, since it is based on the ability to achieve primary containment. Ideally, animal holding and husbandry should be treated within one animal care system, to minimize the potential for any aerosols outside of primary containment, by ensuring that this is as much a closed system as possible. For small animals, such as mice and rats, primary containment will be within the caging system: in micro-isolators or ventilated racks. For larger animals, such as nonhuman primates and canines, the room itself becomes the primary containment. Animal holding room and procedure room configurations can be grouped into three categories: • Dedicated. • Flexible. • Suites. Fig. 2. Typical vivarium corridor arrangements include totally separate research/ husbandry systems; a general “clean” to “dirty” arrangement; and a more contamination-prone shared corridor arrangement. Click to enlarge. Dedicated rooms are animal holding rooms and associated procedure rooms that are specifically designed for a particular species. Typically, access to the animal holding rooms is directly off a corridor, or through adjacent procedure rooms entered off a corridor. Dedicated holding and procedure room arrangements allow for maximum space efficiency because each room’s details are tailored for specific equipment and caging associated with that species. The drawback is limited flexibility, because the rooms cannot be easily used for any other species. Flexible rooms are animal holding rooms and associated procedure rooms that are designed to accommodate a variety of species. Typically, access to the animal holding rooms is through adjacent procedure rooms entered off a corridor, but sometimes the procedure rooms and the holding rooms are designed to be interchangeable (all the rooms being the same size), each being entered directly off the corridor. The rooms are designed to allow for a variety of equipment and caging arrangements that will work for each species being housed there. The price of this flexibility is space efficiency. Each species will have different equipment and caging associated with it, which will require a different room layout and different amounts of square footage. To achieve a room size that works for all the layouts, the largest room size must be used. Suites are groups of animal holding rooms clustered together around shared procedure rooms. The rooms can be designed to be either flexible or dedicated. Suite arrangements allow studies to be isolated within a small group of rooms—physically separated from the other rooms on the floor. This is particularly advantageous for biohazard areas where different agents can be studied with a high level of isolation provided between the suites. Personnel and material flow A vivarium supports two user groups: a community needing access for scientific investigation and a team responsible for the care and welfare of the animals. In addition to the circulation of these two distinct groups of personnel, there is also a steady flow of material and equipment into and out of the facility. Vivarium floor plans revolve around corridor arrangements. Three essential corridor diagrams drive the flow of personnel and materials (Fig. 2, above): • Research/husbandry. • Directional. • Shared. The “research/husbandry” diagram involves the arrangement of corridors such that there is a separation of flow between researchers and husbandry staff. This approach requires a greater area of the floor plan to be dedicated circulation space. It is often used when there needs to be a distinct separation between husbandry and research activities, minimizing the crossing of paths. The “directional” diagram involves the arrangement of corridors such that there is a dedicated clean corridor on one side of the vivarium and a dedicated dirty corridor on the other side, with cross-connecting corridors that allow flow from the clean corridor to the dirty corridor. This does not permit the level of physical separation achieved with the “research/ husbandry” approach, but it maintains the principle of moving from clean to dirty and uses much less space for circulation. This is the approach that is recommended for most vivarium applications. The “shared” diagram involves the arrangement of corridors such that there are no dedicated clean and dirty corridors. Flow from clean to dirty occurs within the same corridor, with constant crossing of paths. This arrangement permits no level of separation between clean and dirty, but it utilizes the least amount of space for circulation. Fig. 3. Vivarium designs must make a basic selection between centralized and distributed cage wash placement. Each layout includes tradeoffs and advantages in terms of efficiency and equipment utilization.Click to enlarge. Besides corridor arrangement, the location of the cage wash must also be considered. It is a major hub of any vivarium facility. Equipment and caging used in studies must be sterilized before being used again for different animal subjects. The needs of the facility have to be carefully evaluated to determine whether the cage wash should be centralized at one floor of the building or distributed on different floors (Fig. 3, left). A centralized cage wash allows for high equipment utilization, greater staff efficiency, and lower equipment cost. The trade-off is having to move equipment and caging over a greater distance to and from the cage wash, including the use of elevators. A distributed cage wash capability allows for reduced travel time, and higher redundancy of equipment. The disadvantages include lower staff efficiency and higher equipment costs. In conclusion, it is important to synchronize the design of a facility with vivarium protocols and practices to avoid disruptive and costly changes after the facility is in operation. For any project, whether it is new construction or a renovation, a consensus must be reached as to which strategies are the most effective, taking into consideration the constraints of limited staffing resources and budget. Sean P. Cuddahy, AIA, LEED AP, is a senior associate and project manager at CUH2A, a multi-office architecture and engineering firm with an emphasis on research facilities. Cuddahy’s experience includes a specialization in vivarium design; clients include both private and public sector organizations. Erik W. Terry, LEED AP, is a senior laboratory and vivarium planner at CUH2A and has focused on a variety of laboratory planning projects for a diverse base of clients including academic, government, pharmaceutical, and biotech organizations.