If you use a squirrel cage without the motor side being sealed there is an issue with some very strong static electricity that can pop and blow as well as deliver a nasty shock. The air passing through the plastic causes the build up and the fine particles inside can become explosive. Similar to a silo dust explosion but on a smaller scale, however will still get your attention!
All I wanted to do when I started this crazyness was build a knife better than I can buy. Now I have to think like an evil scientist and huddle in my dark lab doing millions of esoteric calculations to squeeze that last ounce of performance out of my diabolical inventions.