Why do Chinese etiquette have to knock on the door three times to enter?

Scientifically speaking: Generally, door handles are made of metal. Knocking on the door three times is to release the static electricity on the door to avoid being shocked by static electricity. Most doors open inward, so you have to bend over to get in.

Because the room is a closed space, after opening the door, let the air (dirty things) in the room come out first and then go in. If you go in sideways, the air will jump directly on you.

Opening etiquette:

(1) The door opens inward.

If the door opens inward, the host should first open the door and then invite the elders or guests to enter sideways.

(2) the door that opens outward.

If the door is open to the outside, the host should open the door and invite elders and guests first.

(3) Rotating gate.

If you are accompanying your superiors or guests through the revolving door, you should go there and wait.

No matter what kind of door you enter or leave, the secretary should use both "mouth" and "hand" and be in place when receiving and guiding. That is, the use of gestures should be standardized, and signs such as "please", "please go this way" and "please be careful" should be said at the same time.

I hope my answer is helpful to you.