Vivarium and animal facility airflow control

A vivarium, or animal research facility, places demands on HVAC that combine those of a laboratory, a hospital and a cleanroom. The animals need stable temperature, humidity and air quality, because changes in their environment can affect their welfare and the validity of research. Staff need protection from allergens and, in some facilities, infectious agents. Clean areas must be protected from soiled areas, and some rooms must be isolated from all others.

Airflow control is central to meeting these needs. This guide covers the main requirements, how air valves and ventilated caging are integrated, and how to verify performance.

Governing guidance

In Canada, animal facilities in research institutions follow the guidelines of the Canadian Council on Animal Care (CCAC), including its guidelines on laboratory animal facilities. Many designers also refer to the Guide for the Care and Use of Laboratory Animals (National Research Council), and facilities working with infectious agents must meet the Canadian Biosafety Standard. Building codes, provincial occupational health and safety regulations and the institution's own standards also apply.

These documents generally set performance outcomes rather than prescribing a single design. The institution's animal care committee, veterinarians and biosafety staff should help set design criteria.

Key environmental requirements

Requirements vary by species, housing method and research use. The table describes common practice, not a substitute for the governing guidelines.

Pressure relationships

Vivaria are organized by cleanliness and risk. A typical pressure map includes:

• Clean corridors and barrier suites: positive to surrounding areas to protect animals from contamination.
• Animal holding rooms: positive or negative depending on whether the priority is protecting the animals or containing allergens and agents.
• Quarantine rooms: negative, to keep incoming animals' potential pathogens contained.
• Procedure and necropsy rooms: often negative with local exhaust.
• Cage wash soiled side: negative to the clean side.
• Containment suites: negative, with design per the Canadian Biosafety Standard.

Many rooms need to switch pressure relationships as research programs change, which favours controls that can be reconfigured. Flow offset control is typical; see room pressurization control: offset vs direct pressure.

Why air valves suit vivaria

Pressure-independent air valves are common in animal facilities because they:

• Hold supply and exhaust flows accurately when duct pressures change, protecting pressure relationships.
• Support two-position or variable operation for room mode changes.
• Can include shut-off capability for room decontamination; see shut-off and two-position air valves.
• Have no flow sensor to clog with bedding dust and animal hair.

The last point matters. Exhaust from animal rooms carries dander, bedding particles and hair, which can foul pitot or thermal flow sensors. Exhaust grilles often include pre-filters to protect ductwork.

Ventilated caging

Many rodent facilities use individually ventilated cage (IVC) racks. Each rack supplies filtered air to individual cages and exhausts air from them. IVC racks change how the room airflow is designed.

Rack connection options

1. Unconnected racks: the rack draws supply from and exhausts to the room, with HEPA filtration on exhaust. The room HVAC handles the full heat and odour load.
2. Exhaust-connected racks: rack exhaust is connected directly to the building exhaust system, removing heat, odour and ammonia at the source.
3. Supply and exhaust connected racks: both are connected, giving the most control over cage conditions.

When racks are connected to building exhaust, each connection effectively becomes another exhaust device in the room. Air valves on rack connections, or a room-level controller that accounts for rack exhaust, keep the room offset correct as racks are connected, moved or disconnected. Because cage-level ventilation handles much of the contaminant load, some facilities have reduced room air change rates with veterinary approval.

Temperature and humidity control

Animal rooms need tight temperature control, often within a narrower band than offices. Each room usually has its own reheat coil and temperature sensor. High room air change rates and 100 percent outdoor air make reheat a major energy consumer.

Humidity is a particular challenge in Canada. Winter outdoor air is very dry, and without humidification indoor RH can fall well below 30 percent. Steam or adiabatic humidification at the air handler, sometimes with room-level trim, maintains the required range. See humidification in cold climates.

Reliability and alarms

Animals can suffer quickly if HVAC fails. Common reliability features:

• Redundant supply and exhaust fans, often N+1.
• Emergency power for fans and critical controls.
• Room-level alarms for high and low temperature, humidity and pressure, reported to staff 24 hours a day.
• Redundant heating and cooling sources.
• Monitoring of IVC rack blower status where connected.

Energy opportunities

Vivaria are energy intensive. Opportunities include heat recovery on exhaust using methods that avoid cross-contamination, such as run-around loops; reduced air changes in rooms with connected IVC racks where veterinary staff agree; and optimized temperature reset of supply air to reduce reheat.

Verification

Commissioning and periodic verification should include:

1. Measured supply and exhaust flows and air change rates in each room.
2. Pressure direction for every room in the pressure map, with smoke at doors.
3. Temperature and humidity stability over time, from trends.
4. Room mode changes, checking for pressure reversals.
5. IVC rack connection effects on room offset.
6. Alarm testing and emergency power operation.

Thorough building commissioning before animals are introduced avoids disruptive adjustments later.

Key takeaways

• Vivaria combine lab, healthcare and cleanroom demands, guided in Canada by CCAC guidelines and the Canadian Biosafety Standard.
• Room air changes, temperature, humidity and pressure must be stable for animal welfare and research validity.
• Pressure-independent air valves suit vivaria because they hold flows accurately and resist fouling from bedding and hair.
• Connected ventilated cage racks change room airflow design and must be accounted for in offsets.
• Redundancy, continuous alarms and thorough verification protect animals from HVAC failures.