PSA I was just scrolling YouTube when I came across a video from A Current Affair Australia about potting mix almost killing an elderly man. What he had breathed from the potting mix almost killed him. For many years when starting we never wore a mask when dealing with perlite. Under a microscope perlite looks like shards of glass. I recommend never opening a bag of it inside, go outside for a second and dump your perlite in your mix. As a safety I guess we should always wear a mask when mixing soil.