Glass flasks should be taped with friction tape or placed in a metal container large enough to hold the flask. If this is not possible, a safety shield should be placed between the flask and the operator. The vessel should be inspected for cracks or scratches before use. Only round bottomed or thick walled flat bottomed flasks specifically designed for vacuum work should be used. Ordinary glass ware, especially flat bottomed flasks, is not intended for vacuum work and may burst.
Dewar flasks are capable of imploding from thermal shock or a very slight scratch.
They should be wrapped with friction tape all the way up the neck or shielded in a wooden or metal container to guard against flying glass in case of an implosion. Glass vacuum desiccators should be made of glass specifically designed for vacuum work. They should be enclosed in a shield or wrapped in friction tape. The reaction flask should be taped and placed in a wire cage. The distillation should be performed behind an explosion shield.