Someone should build a big ol terrarium for insects, with an increased O2 atmosphere, let us see just how big we can get em to grow.
Imagine a bumblebee the size of a dog in a 30% O2 atmosphere
Paleontologist here.
Though giant insects were around during periods of high atmospheric oxygen, there were other periods of time with giant bugs that had oxygen levels comparable to today.
Basically what I’m saying is you probably wouldn’t need an oxygen chamber, you’d just need to breed em big.