Final answer:
Coat hangers should not be used as gas welding filler metals due to their unsuitability for welding, potential to create weak joints, and risk of releasing harmful fumes.
Step-by-step explanation:
Coat hangers should not be used as gas welding filler metals because they are not designed for welding and could lead to weak joints and potential structural failures. Welding requires specific materials that meet the standards for safety, strength, and reliability. Moreover, coat hangers might contain unknown impurities and coatings that can cause inconsistent melting points, poor bonding with the base metals, and could potentially release harmful fumes when subjected to the high temperatures of welding. The correct filler metal should always be used to ensure the integrity and strength of the weld.