Chris is welding on his sculpture, sparks and electricity is flying, he's wearing his welding goggles, however when he stops, he pulls away and is turning a cutting torch off. The torch does not produce sparks and electricity like a welder does.
When Maggie is reading from the entomology textbook, she says that in one gram of dust, researchers found 6,893 mites. She then says that it was in only an ounce of dust.