Animal room temperature and humidity measurement is a fundamental environmental qualification and monitoring activity for laboratory animal facilities, verifying that vivarium conditions remain within the limits specified in GB 14925 and internationally recognized laboratory animal care guidelines. Accurate determination of room temperature, daily temperature fluctuation, and relative humidity protects animal welfare, safeguards the reproducibility of in vivo studies, and supports GLP compliance. This article outlines the applicable standards, test objects, testing items, measurement methods, and practical considerations for animal room temperature and humidity testing performed by accredited third-party laboratories.
Technical Overview
Animal room temperature and humidity measurement refers to the systematic determination of air temperature and relative humidity in laboratory animal housing facilities using calibrated instruments at defined locations and over defined time periods. The objective is to verify that the housing environment continuously meets the limits established by facility design specifications, national standards, and regulatory requirements. Because laboratory animals spend their entire lives within the macro-environment of the room and the micro-environment of the cage, even modest deviations in temperature or humidity can alter thermoregulation, metabolism, reproduction, immune function, and behavior, ultimately compromising both animal welfare and the validity of experimental data.
In China, GB 14925 (Laboratory animal — Requirements of environment and housing facilities) defines environmental classes for animal facilities, including conventional, barrier, and isolation environments, and specifies limit values for temperature, daily temperature fluctuation, and relative humidity for commonly housed species. Internationally, the ISO 14644 series of standards, adopted in China as the GB/T 25915 series, provides general test methodology for temperature and humidity determination in controlled environments such as barrier rooms operated according to cleanroom principles. Together, these standards form the technical basis on which accredited third-party laboratories design measurement schemes, perform on-site testing, and issue compliance reports.
Typical specification values referenced during facility qualification and routine verification include:
- Temperature for mice and rats: commonly 20–26°C under GB 14925.
- Temperature for larger species such as rabbits, dogs, cats, minipigs, and non-human primates: commonly 16–26°C.
- Relative humidity: 40–70% RH under GB 14925, with many international programs operating within 30–70% RH.
- Daily temperature fluctuation: generally limited to 3–4°C depending on the environmental class of the facility.
Testing Samples
In environmental testing, the sample is the environment itself rather than a physical product. Temperature and humidity measurement is typically performed on the following categories of animal housing environments and associated equipment:
Conventional Environment Animal Rooms
Open rooms with filtered but non-sterile ventilation that house species such as rabbits, dogs, cats, and non-human primates under standard hygiene conditions. Because these rooms interact more directly with the external climate, temperature and humidity verification across different seasons is particularly important.
Barrier Environment Animal Rooms
Positive-pressure rooms supplied with HEPA-filtered air that house specific pathogen free (SPF) mice and rats. Barrier rooms are frequently operated to cleanroom principles, so temperature and humidity measurement is often performed alongside ISO 14644 or GB/T 25915 verification of air cleanliness, airflow velocity, air change rate, and pressure cascade.
Isolation Environments and IVC Systems
Isolators for germ-free and gnotobiotic animals, as well as individually ventilated cage (IVC) racks, create micro-environments in which temperature and humidity can differ measurably from the room values. Measurement programs for these systems may include both room-level points and in-cage measurement points to characterize the conditions actually experienced by the animals.
Functional Support Areas
Quarantine suites, breeding rooms, procedure and surgery rooms, and cage wash areas. Although these spaces may not permanently house animals, their environmental conditions affect animal transport, recovery, and operational hygiene, and are often included in comprehensive facility qualification programs.
Testing Items
A complete temperature and humidity evaluation of an animal facility typically covers the following items, each of which is compared against the acceptance criteria derived from the applicable standard and the facility design specification:
- Indoor air temperature: determination of the temperature at representative points within the animal activity zone, confirming that all readings fall within the specified range.
- Daily temperature fluctuation: the difference between the maximum and minimum temperature recorded over a full 24-hour operating cycle, used to assess the stability of the environmental control system.
- Relative humidity: determination of relative humidity within the animal activity zone, confirming compliance with the specified lower and upper limits.
- Diurnal humidity variation: the range of relative humidity over a 24-hour cycle, which reflects the interaction of ventilation, moisture loads, and humidification or dehumidification equipment.
- Spatial uniformity: the difference between the highest and lowest readings across all measuring points at the same time, used to evaluate temperature and humidity distribution within the room.
- Continuous monitoring system verification: comparison of permanently installed monitoring sensors against calibrated reference instruments to confirm the reliability of routine records and alarm functions.
Testing Methods
Temperature and humidity measurement in animal rooms follows a structured protocol covering instrumentation, point selection, measurement execution, and data evaluation. Accredited third-party laboratories typically conduct testing in accordance with the test provisions of GB 14925 and, where applicable, the general measurement methods of the ISO 14644 or GB/T 25915 series.
Instrumentation and Calibration
Testing is performed with calibrated digital thermohygrometers and temperature and humidity data loggers. Recommended instrument performance includes a temperature accuracy of ±0.5°C or better, a humidity accuracy of ±3% to ±5% RH, and a resolution of 0.1°C and 0.1% RH. All instruments must hold calibration certificates traceable to national metrology standards, the calibration must remain valid on the date of testing, and recalibration is normally required at intervals not exceeding one year.
Selection and Arrangement of Measuring Points
Measuring points are placed within the animal activity zone, commonly 0.5 to 1.5 meters above the floor at cage rack level. Points are distributed diagonally or on a grid pattern so that all representative areas of the room, including corners and rack positions, are covered; the number of points is increased in proportion to the room area. Points are positioned away from air supply diffusers, exhaust grilles, doorways, heat-generating equipment, and direct sunlight to avoid unrepresentative local readings. For IVC and isolator systems, additional measurement points may be placed inside the cage or isolator chamber.
Measurement Procedure
Before measurement, the HVAC system must operate in its normal automatic mode with the room at design occupancy or an equivalent simulated load, and conditions must be allowed to stabilize. For spot verification, readings are taken at all measuring points after the instruments have equilibrated, which generally requires at least 10 to 15 minutes at each location, with repeat readings taken to confirm stability. For the determination of daily fluctuation, calibrated data loggers record continuously at intervals of typically 10 to 30 minutes over a minimum of 24 hours, and preferably 48 to 72 hours, so that the full day-night cycle, lighting program, and operational events are captured.
Data Evaluation and Reporting
Measurement results are evaluated point by point against the acceptance criteria. Compliance requires that every measuring point remains within the specified temperature and humidity range throughout the observation period and that the calculated daily fluctuation does not exceed the permitted limit. The test report should identify the facility and rooms tested, the environmental class and species-specific limits applied, instrument models and calibration status, a schematic of the measuring point layout, summarized maximum, minimum, and average values, a statement of conformity, and documentation of any deviations observed during testing.
Applications
Temperature and humidity measurement data from animal rooms serve multiple compliance, quality, and scientific purposes across the life sciences sector:
- Facility commissioning and acceptance testing of newly built or renovated vivariums, confirming that HVAC performance meets design specifications before animals are introduced.
- Periodic verification supporting laboratory animal facility licensing and the maintenance of internationally recognized accreditation programs for laboratory animal care and use.
- GLP compliance support, providing documented environmental evidence for preclinical safety studies in which environmental conditions are an auditable element of study integrity.
- HVAC validation, retrofit qualification, and troubleshooting, using measured data to identify zones with poor uniformity, excessive fluctuation, or inadequate humidification control.
- Research data integrity, supplying environmental records that strengthen the reproducibility and credibility of published in vivo findings.
- Animal welfare assurance, demonstrating that housing conditions remain within physiological comfort ranges for each species on a continuous basis.
FAQ
What temperature and humidity should an animal room maintain?
Under GB 14925, mice and rats are typically maintained at 20–26°C, larger species at 16–26°C, and relative humidity at 40–70% RH, with daily temperature fluctuation generally limited to 3–4°C depending on the environmental class. The exact setpoints and tolerances should always be confirmed against the species-specific limits and the facility design specification.
How often should temperature and humidity be measured?
Permanently installed monitoring systems should operate continuously, and their records should be reviewed routinely. Independent verification by accredited third-party laboratories is commonly performed at facility commissioning, after major HVAC modification or relocation, and at least annually, with additional seasonal checks recommended for conventional environment rooms.
Where should sensors be placed in the room?
Sensors belong in the animal activity zone, typically 0.5 to 1.5 meters above the floor at cage rack height, at representative points distributed across the room and positioned away from air supply diffusers, exhausts, doors, heat sources, and direct sunlight. For IVC racks and isolators, in-cage measurement points provide a more accurate picture of the animals' actual exposure.
What instruments are used, and how are they calibrated?
Calibrated digital thermohygrometers and continuous data loggers are used, with a recommended temperature accuracy of ±0.5°C or better and humidity accuracy of ±3% to ±5% RH. Instruments must be traceable to national metrology standards, hold valid calibration certificates at the time of testing, and be recalibrated at intervals not exceeding one year.
How long does a measurement take?
Spot verification at multiple points can typically be completed within a few hours after the room conditions and instruments have stabilized. Determination of daily temperature and humidity fluctuation requires at least 24 hours of continuous logging, and 48 to 72 hours or longer is recommended to fully characterize stability under real operating cycles.
What happens if the results are out of specification?
An out-of-specification result triggers a structured response: confirmation of the readings through re-measurement, investigation of HVAC performance and control settings, assessment of the potential impact on housed animals and ongoing studies, implementation of corrective actions, and repeat testing to demonstrate restored compliance. All findings and actions should be documented within the facility deviation and corrective action system.