Fused filament fabrication 3D printers, which are commonly used in non-industrial indoor environments, emit gases and particles that may deteriorate indoor air quality, and adversely impact human health. This study characterized particle and chemical emissions from various 3D printers using an established test method and controlled environmental chamber. High concentrations of ultrafine particles, and numerous hazardous volatile organic compounds were observed during printing. The emissions are due to heating of the filament and varied depending on print conditions and filament and printer properties. Particle toxicity was assessed using various methods, and exposure concentrations were estimated using a model.