There is provided a moisture indicator for a heat and moisture exchange (HME) device that uses a pre-colorant and an activator applied to an inner surface of the HME device. The colorant undergoes a color change of Delta E (&Dgr；E) of equal to or greater than 3 units upon exposure to moisture but not upon exposure to high humidity. The colorant is visually obvious to the unaided human eye under normal light conditions through the body of the device. The HME device with the visual indicator for moisture can indicate to the care-giver that it is time to change the HME device.
