That "if possible" is terrible advice. If you're working with a ceramic fiber blanket, always wear a respirator. And the fibers will continue to hang in the air

That "if possible" is terrible advice. If you're working with a ceramic fiber blanket, always wear a respirator. And the fibers will continue to hang in the air afterward, just like asbestos. High temperature turns the fibers from irritants into carcinogens like asbestos. The suggestion to build one of these things with an uncoated ceramic fiber blanket is horribly negligent.