They are printed with moisture sensitive spots, which respond to various levels of humidity with a visible colour change from blue to pink. The humidity inside dry packed barrier bags can be monitored by including a HIC inside.
When the bag is opened, the card can be examined for proper dryness inside the bag. This indicated that the barrier bag and the desiccants are functioned correctly. Complies with IPC/JEDEC J-STD-033 MIL-L-8835.