Final answer:
Chisels and other impact tools with mushroomed heads are considered unsafe and should be removed from use due to the risk of metal shards breaking off and causing injury.
Step-by-step explanation:
Impact tools, such as chisels, with mushroom heads should be removed from use. When a chisel head mushrooms, it means that the metal has deformed and spread out to the sides, often as a result of repeated hammering. This can create dangerous conditions, since small pieces of metal can break off the deformed head and fly off as dangerous projectiles during use. Therefore, for safety reasons, it's crucial to regularly inspect impact tools and replace any with mushroomed heads.