Humidity Indicator Cards – FAQs

After the card turns pink, do I need to replace it?

No. The card will turn from pink back to blue once it is exposed to an atmosphere that is dryer than the rating on the card.

Note: Non-reversible Humidity Cards (Maximum Humidity Indicators) will not return to the original color once exposed to moisture.

How long will it take for the card to turn from blue to pink (or pink to blue)?

The time it takes for the card to turn from one color to the other depends on the amount of humidity the card is exposed to and the temperature of exposure. Normally, the cards will change color within minutes of exposure to the ambient conditions.

Note: Non-reversible Humidity Cards (Maximum Humidity Indicators) will not return to the original color once exposed to moisture.

What is the effect on temperature on the cards? Will they still work?

The humidity rating on the cards changes at the rate of 2-1/2% of rated value per 10°F away from 75°F.  That is, for a card that is rated at 30%, when viewing it at a temperature of 35°, the true value becomes 27%.  (2.5 x 4 = 10% rating change, applied to a rating of 30% = 3%, 30% – 3% = 27%.) It works in the opposite direction for higher temperatures.

Can I get a custom humidity indicator?

Yes. AGM’s Engineering Department has designed hundreds of modified and custom versions for previous customers.