The UL Research Institutes new study of five metal-filled FDM filaments found that, compared with conventional polymer filaments, metal composites generally emitted fewer particles by number and lower levels of VOCs (fumes). Downside: the size of emitted matter was larger but mostly still below 1 micron. Relatively little of the embedded metal powder becomes airborne during printing, researchers found. The paper does not name the filament brand, but the tested lineup very closely matches Markforged’s Metal X material system.