Humidity indicator card
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A humidity indicator card (HIC) is a card on which a moisture-sensitive chemical is impregnated such that it will change color when the indicated relative humidity is exceeded. This is usually blotting paper impregnated with cobalt(II) chloride base, or less toxic, copper(II) chloride base.
This item is an inexpensive way to quantify relative humidity levels inside sealed packaging. They are available in many configurations and used in many applications, especially military and semiconductor. The most common humidity indicator cards change color from blue (less than indicated RH level) to pink (greater than indicated RH level). United States Military Specification Mil-I-8835A is the governing specification for a humidity indicator card. The humidity indicator card is also specified for use in J-STD-033 which is the standard for Handling, Packing, Shipping and Use of Moisture/Reflow Sensitive Surface Mount Devices, also known generically as semiconductors. This is a joint standard developed by the Joint Electron Device Engineering Council and IPC and is used in semiconductor packaging.
The need for an easily read humidity indicator that could not be damaged by vibration was identified during World War II. Rear Admiral Welford C. Blinn, at that time the Commander of the USS Pope, became concerned about the poor condition of the weapons and ammunition arriving in the Pacific Theater. High humidity in the South Pacific, coupled with poor packaging methods, was causing corrosion and moisture damage. A significant amount of ordnance was arriving in an unstable, and sometimes dangerous, condition. Following the end of the war Rear Admiral Blinn was assigned to Washington, D.C., where he had the use of a research lab. There he developed the concept for the first color change humidity indicator, a simple “go/no-go” method of monitoring humidity.
In the late 1940s, Relative Humidity in the range of 30-35% was the concern because this is when corrosion can begin. For 50 years, industrial and military applications for color change humidity indicators were the primary market for these products. R. Admiral Blinn founded Humidial Corporation in 1948 Acquired by Süd-Chemie, Inc., in 1989 to commercialize humidity indicators, later acquired by Clariant [2]
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