Laboratory animals are essential research models in life science, bridging basic cell & molecular research and clinical translation. A large proportion of SCI papers rely on animal studies. Proper animal housing directly determines the reliability of experimental data and impacts biomedicine, pharmacology and gene research.

I. Adverse Effects of Unqualified Environmental Parameters on Animals & Research Data

SPF barrier animal labs must comply with national mandatory standards covering temperature, humidity, air change rate, pressure differential, cleanliness, ammonia concentration and noise. Any out-of-spec parameter causes irreversible harm to animals and invalidates experiments.

1. Temperature fluctuation The national standard range is 20℃–26℃. Mice easily get agitated above 24℃. Temperature swings disrupt animal physiology and metabolism, altering drug absorption and excretion and ruining test results. In practice, designers tighten the working range to 20℃–24℃. Animal labs run 24/7 all year. HVAC load calculation must adopt local extreme high/low temperature data instead of conventional building meteorological parameters. Many low-budget projects use ordinary air-cooled units, suffering severe performance decay in summer and winter. Temperature fluctuations over 3℃ directly invalidate pharmacological control tests and lead to costly later retrofits.
2. Excessive humidity High humidity weakens animal immunity and accelerates pathogens and parasites, raising cross-contamination risks. Bedding and animal waste continuously release moisture. The cooling coil of the air-handling unit must reserve sufficient dehumidification capacity. Insufficient dehumidification causes condensation and mold on walls and cage racks, threatening the whole barrier sterile environment.
3. Excessive noise The regulatory noise limit is ≤60dB(A), yet even this level damages rodents: reduced immune activity in mice and hypertension, abnormal hormone levels in rats. For reliable tests, indoor noise should be controlled below 50dB(A). Many designs only mark noise limits on drawings but ignore vibration isolation and sound insulation. Fan resonance and airflow noise disturb animals, creating inconsistent physiological baselines between control and test groups.

II. Core HVAC Design Challenges for SPF Animal Laboratories

HVAC design focuses on constant temperature & humidity, air change rate and noise control. Proper control of these three factors helps maintain cleanliness, ammonia level and settling bacteria within limits. Four major challenges are summarized below:

(1) Year-round thermal load and cold/heat source arrangement

Animal labs operate continuously. Transitional seasons bring conflicting demands: cooling during warm days and heating at cold nights. Shared cold-heat units switch frequently, resulting in poor precision and fast wear. The optimal solution is separate cooling and heating sources. If only one heat pump unit can be used, backup regulation systems are required to prevent environmental failure. Frequent heat-cool cycling shortens compressor service life and increases long-term OPEX for nonstop operation.

(2) Redundant backup for key equipment

Circulation fans are mandatory to be configured as one running + one standby. Chillers and water pumps are recommended with backup units as well. If critical equipment fails without standby units, fresh air/exhaust stops, ammonia accumulates rapidly and lab animals die from stress. This may cause massive sample loss and delayed research schedules. Backup equipment is a cost-effective safeguard against catastrophic losses.

(3) Precise narrow temperature control

The national standard temperature band is only the minimum compliance requirement, not the ideal housing condition for rodents. Designers narrow the range to 20℃–24℃ and calculate loads based on local extreme weather. This ensures consistent comparison across batches and seasons, meeting CNAS and new drug application audit requirements for CRO and biotech clients.

(4) Low-noise system construction

The 60dB(A) limit is just the baseline. To avoid noise-induced physiological changes in animals, designers combine fan vibration dampers, flexible duct connectors, machine room acoustic panels and silencers to keep indoor noise around 50dB(A). Relying merely on terminal silencers cannot meet the low-noise housing requirement.