Short term exposure of small fiber specimens to non-standard atmospheric conditions can cause errors in their strength measurement. Experiments were conducted to evaluate the effect of local humidity changes on the strength measurement. Production model HVI systems (one from vendor) were equipped with humidity sensors near their specimen brushing stations. One system was more sensitive to short term humidity cycles (1.15 compared to 0.6 gf/tex/%RH) while the other system was most sensitive to sample precondition in (1.81 for equilibrium compared to 0.6% gf/tex/%RH) for humidity cycling). Both instruments indicated a wide range of strength-humidity sensitivity among the 61 cottons surveyed.