Which item is NOT solid waste produced by welders?

• A. Filtered air from an environmentally friendly exhaust
• B. Metal shavings
• C. Used oil
• D. Scrap metal

Answer: (A)

The main idea is that waste types in welding differ by state: solid waste, liquids, and gases. Metal shavings and scrap metal are physical solids left over from cutting and grinding, so they’re clearly solid waste. Used oil is a liquid waste that carries contaminants and requires proper hazardous waste handling. The filtered air from an exhaust, however, is a gas—air that’s being moved or vented, not a solid residue. Even when filtered, it isn’t a solid byproduct, so it isn’t solid waste. Therefore, the item that isn’t solid waste is the filtered air from the exhaust.