What is the hole in the ballpoint pen cap?

As everyone knows, when a child catches something, he will put it in his mouth. Therefore, the accident that the child swallows the ballpoint pen cap often occurs, which is easy to cause suffocation. However, if the child swallows the cap, he can barely breathe. This will give the medical staff some time, and a fresh life may be saved. What is the hole in the ballpoint pen cap?
In China's "General Requirements for the Safety of Student Supplies", it is stipulated that the pen cap of the writing pen, marker pen, correction pen, and watercolor pen should meet at least the cap size (the child can't swallow it when it is large enough), and the cap cap ventilation area (with small holes) If you accidentally swallow it without suffocation) or the cap is ventilated (there are objects such as hooks that can maintain a certain amount of air circulation when inadvertently swallowed).