Apple has indicated that using AirTags with batteries covered in a bitter coating may not work because the coating can block the contacts and cause the batteries to stop working.
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This may sound like an arbitrary issue to point out, but it comes on the heels of a recent statement from the Australian Competition & Consumer Commission (ACCC) about Apple AirTags. According to the ACCC, there are concerns about how easy it is to access the battery compartment of an AirTag, which contains a small battery that could be swallowed by a child.
A common way for product makers to discourage children from swallowing small parts like coin batteries or Nintendo Switch games is to coat the part with a bitter substance. The nontoxic coating gives the item a bad taste, deterring children from putting it in their mouths. However, Apple warns that the coating may obstruct the battery contacts inside the AirTag compartment, preventing it from working properly.
Apple has updated its AirTag battery replacement page with this information, and added a choking hazard warning. It also recommends that when replacing an AirTag battery, you ensure the compartment is fully closed. The ACCC notes that while AirTags emit a tone when the compartment lid contacts the battery, this does not indicate that the compartment is securely locked. To ensure the compartment is securely locked, Apple says you should twist the lid until it stops.