Standardized Range
Standardized ranges for temperature and humidity ensure that textile tests performed in different parts of the world produce comparable results. The iso 139 environmental tolerance specifies a standard atmosphere of 20 degrees Celsius and sixty-five percent relative humidity for the conditioning and testing of fabrics. It also defines the allowable fluctuations around these setpoints during the duration of the measurement.
Laboratory Compliance
Specialized air conditioning systems are required to maintain the environment within the narrow limits of iso 139 environmental tolerance. A standard lab must stay within plus or minus 2 degrees Celsius and plus or minus four percent relative humidity. For high precision work, the tolerance is tightened to half of those values to minimize the impact on sensitive moisture measurements.
Result Accuracy
Fiber properties like tensile strength and electrical resistance change as the material absorbs or releases water from the air. Without adhering to iso 139 environmental tolerance, a mill might report a breaking strength that is ten percent higher or lower simply because the lab was too dry or too damp. Uniformity across the industry allows buyers to trust the data sheets provided by different suppliers.
Environmental Constraint
Certification of a laboratory requires continuous recording of the room conditions to prove that no excursions occurred. If the power fails or the climate control breaks down, the results of any tests in progress are invalidated. These rules stop being applied once the fabric leaves the controlled environment, as real world performance is subject to much wider weather variations.
