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Temperature, Humidity, and Environmental Control in Animal Facilities
Created on 02.06
Temperature: 18–26 °C | Humidity: 40–70% | 24-Hour Continuous Operation
In the fields of life science and biomedical research, an animal facility is far more than a simple “room.” Its internal environment directly affects animal welfare, health status, and—most critically—the reliability and reproducibility of scientific data. Among all environmental parameters, precise and stable control of temperature and humidity forms the foundation of environmental management. Defining operating conditions as 18–26 °C temperature, 40–70% relative humidity, and 24-hour continuous stability is not arbitrary, but a requirement grounded in science, regulations, and ethical responsibility.
I. Understanding the Standards: The Science Behind the Numbers
1. Temperature Range (18–26 °C)
Most commonly used laboratory animals, such as mice and rats, are homeothermic. Their metabolism, physiological activity, immune responses, and behavior are highly sensitive to ambient temperature. This range corresponds to their thermoneutral zone, minimizing physiological stress and maintaining stable basal metabolism. As a result, experimental background variability is reduced and data integrity is preserved.
2. Humidity Range (40–70%)
Relative humidity directly influences animals’ perceived temperature, respiratory mucosal health, and skin integrity.
- Low humidity (<40%)
may cause dehydration, dry and cracked skin, and increased risk of respiratory disorders.
- High humidity (>70%)
promotes the growth of microorganisms such as bacteria and fungi, leading to damp or moldy bedding and increased disease risk.
The 40–70% range is critical for maintaining water balance and protecting natural physiological barriers.
3. 24-Hour Stable Operation
Animal circadian rhythms (biological clocks) are closely linked to environmental conditions. Excessive day–night fluctuations in temperature or humidity can disrupt sleep, feeding behavior, endocrine cycles, and stress responses, introducing uncontrollable experimental variables. Therefore, environmental control systems must operate continuously, preventing parameter drift caused by equipment shutdowns or failures.
II. Technical Challenges and Key Control Strategies
Maintaining continuous stability within these parameters presents several technical challenges that require a systematic engineering approach:
Challenge 1: External Climate and Internal Load Variations
Seasonal changes, personnel movement, heat dissipation from equipment (such as cage washers and autoclaves), and metabolic heat generated by animals all contribute to fluctuating thermal and humidity loads.
Challenge 2: Environmental Uniformity
Temperature and humidity gradients must be avoided within animal rooms. Areas near supply or return air outlets, as well as upper and lower zones, should not form “dead spots,” ensuring a consistent microenvironment for all animals.
Key Control Measures:
- High-precision HVAC systems
equipped with sensitive temperature and humidity sensors, fast-response cooling, heating, humidification, and dehumidification components, and advanced automatic control systems (DDC or PLC) for real-time adjustment.
- Optimized airflow design
, based on engineering calculations, to ensure uniform air distribution and effective removal of heat, moisture, and contaminants.
- Redundancy and continuous monitoring
, including backup compressors and fans, stable power supply systems, and 24/7 monitoring with alarm functions that immediately alert operators when parameters deviate from set limits.
III. Risks of Environmental Control Failure
Loss of temperature and humidity control can lead to serious consequences:
Impact on Research Outcomes:
- Data deviation and poor reproducibility
: Stress responses alter blood parameters, hormone levels, gene expression, and behavior, compromising experimental validity and reproducibility.
- Invalid animal models
: Environmental stress may alter or exacerbate disease phenotypes, leading to misleading conclusions.
- Resource waste
: Interrupted experiments, animal loss, and discarded samples result in significant time and financial losses.
Impact on Animal Welfare:
- Physiological and behavioral stress
, including discomfort, anxiety, and abnormal behaviors.
- Deterioration of health
, with increased incidence of respiratory and skin diseases and higher mortality rates.
IV. Beyond Parameters: An Integrated Environmental Management System
Strict temperature and humidity control must be embedded within a comprehensive environmental management framework to achieve maximum effectiveness:
- Integrated control
with air change rates (typically 10–20 air changes per hour), pressure differentials (ensuring airflow from clean to contaminated zones), and lighting cycles (controlled light–dark rhythms).
- Regular validation and maintenance
, including routine environmental monitoring, sensor calibration, performance qualification (empty and fully loaded tests), and preventive maintenance with complete documentation.
- Compliance with regulations and guidelines
, including China’s Laboratory Animal – Environment and Facilities (GB 14925), international AAALAC accreditation requirements, and the Guide for the Care and Use of Laboratory Animals.
Conclusion
Defining environmental control targets in animal facilities as 18–26 °C temperature, 40–70% relative humidity, and 24-hour continuous stable operation is a deliberate and scientifically justified decision. It reflects modern life-science research’s commitment to experimental standardization, ethical animal welfare, and data quality. Achieving this goal relies on professional engineering design, high-performance equipment, meticulous daily operation and maintenance, and rigorous quality management. Only by securing this environmental foundation can scientific research be built on a reliable and credible basis, providing valid support for advances in biomedical science.
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