What does "can be reused 20x" mean if they don't require recharging?

Yes sometimes you don't need to recharge it. Rainy days go to pink, sunny days go to blue again. If you change humidity level lower, they can go back to blue again. You can use hair dryer or sunlight to lower humidity level. Thank you.

What country are these manufactured in?

They are manufactured in South Korea.

Are they safe to use in food containers?

No they are not safe for food. Thank you.

Hi, are these cobalt-dichloride or cobalt-chloride free? when do they expire?

Blue to pink humidity indicator cards contain cobalt chloride. There's no expiration date on humidity indicator cards. As long as you keep them in tight sealed container with silica gel packet, they will last for long time. Humidity indicator cards are sensitive to temperature, humidity, atmospheric pressure, and wind. Therefore, they do not work well in open air. They work well and display accurate relative humidity level in enclosed space. The humidity card itself is reusable. When the humidity level is high, the dots will change from blue to pink and when the humidity level is low, the dots will change from pink to blue again. With long use, the color of the dots may fade away. Then, you can replace the card. We do carry cobalt free humidity indicator cards (green to purple). You type ASIN B01DYOR0WY in Amazon search bar. Color change is not as clear as blue to pink (cobalt chloride) cards. Thank you.

Product Dimensions	12.7 x 11.18 x 0.76 cm; 9.07 g
Part number	DDHUMID20PK-6 DOT
Manufacturer	Dry & Dry
Item model number	DDINCCRD10
ASIN	B01974FX42

Dry & Dry Premium Humidity Indicator Cards 20 Pack(Reusable) - 10-60% 6 Spot(20 Cards)

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