Humidity Indicator Cards, also known as humidity cards and moisture-proof labels, are cards used to display the humidity of a sealed space. They are environmental measurement products that check whether the relative humidity in a sealed package is safe. The percentage data above or to the side of the circle is the relative humidity data indicated by the corresponding circle.

There are two types of humidity indicator cards, one is a cobalt-containing humidity indicator card, and the other is a cobalt-free humidity indicator card. Their color change principle is as follows:

The principle of discoloration of the cobalt-containing humidity indicator card is based on the principle of color change of the substance produced by the absorption of cobalt chloride. [Co(H20)4Cl2] is blue [Co(H2O)6]2+ is pink, and the humidity card is dry when dry. Blue [Co(H20)4Cl2], changed from blue to pink [Co(H2O)6]2+ after moisture absorption. If the color in the circle changes from blue to pink, it means the humidity inside the package. The relative humidity value corresponding to the circle is reached or exceeded. Another thing to note is that the cobalt-containing humidity indicator card is not environmentally friendly and does not meet the latest EU export standards.

The cobalt-free humidity indicator card does not contain cobalt chloride. The color change uses other types of more environmentally friendly chemicals (commercial secrets, so it is inconvenient to disclose the specific substances in detail); blue to blue, blue to purple, yellow to green, yellow to blue, brown Several kinds of blue, brown and green. Similarly, if the color in the circle changes from a dry color to a hygroscopic color, it means that the humidity in the package has reached or exceeded the relative humidity value of the circle. The cobalt-free humidity indicator card is an environmentally friendly product that meets the latest EU export standards.