Conditioning Room ISO 139

Moisture Equilibrium

Natural and synthetic fibres absorb moisture from the surrounding air, which alters their weight and strength. When a specimen enters the conditioning room ISO 139, it must remain there until it reaches constant mass, meaning successive weighings at intervals of two hours show less than one-tenth of a percent difference. Pre-conditioning the sample at a lower humidity beforehand ensures it approaches this state from a dry starting point.

This prevents hysteretic differences in final moisture content.

Verification Protocol

Continuous monitoring through calibrated sensors confirms that the space meets the required specifications. Automated data loggers track the temperature to within plus or minus two degrees and relative humidity to within plus or minus four percent. For high-precision reference work, the standard demands closer limits of half these ranges.

Readings must be taken at multiple points to guarantee uniformity throughout the entire volume of the chamber.

Operational Limit

Any variation in air circulation or sudden opening of doors disrupts the stability of the testing environment. Rapid fluctuations can yield invalid tensile or tear strength recovery results because the physical response of a yarn or fabric is highly sensitive to moisture changes. Heavy machinery should be placed outside the room to prevent heat transfer.

Smaller labs must use double-door airlocks to maintain the equilibrium of the conditioned volume.