how do they put air in bubble wrap?

Question

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Answer 1

Rather than blowing air into individual cells bubble wrap is made by fusing two sheets of plastic together with heat. To form the bubbles one of the fuser plates (or drum) has holes in it. A vacuum sucks the plastic into the holes then the backer sheet is applies and heated to fuse onto the fist sheet. This will trap a pocket of air in a formed bubble.

Answer 2

probably like this.
seal two plastic sheets with enough air in between.
flatten it out so that the air is equally distributed.
Then using some sort of a heated die with circular cavities, this sealed layers of plastics are pressed together.
This will for bubbles with air in it.

Answer 3

Small tweezers.