Fused deposition modeling (FDM) printers, the more common type of desktop 3D printers, emit volatile gases and particulates that may deteriorate indoor air quality. The developed method for characterizing and quantifying emissions from an operating 3D printer measures fine particulate and volatile organic compound (VOC) concentrations over time using an environment controlled testing chamber. All tested printers emitted ultrafine particulates (UFP). Approximately 70% of the particulates released from the printers were less than 50 nm in diameter. Emitted UFPs increased in size over time by coagulating with other particles and condensation of printer-generated vapors. Chemical compositions of the released gases varied depending on the filament material. Volatile chemicals such as styrene and ethylbenzene were released from acrylonitrile butadiene styrene (ABS) filament. Caprolactam, originating from a nylon filament, was a predominant released gas. Though polylactic acid (PLA) filament is thought to be safer since it is biodegradable, PLA still released chemicals such as methyl methacrylate. Acetaldehyde and formaldehyde were released from all the studied filaments. ABS emitted more particles than PLA or nylon filaments. The extrusion nozzle temperature on the printer had the greatest effect on both particles and VOC emissions; the emissions increased as the temperature of the nozzle increased. Depending on the maker of the filaments, the total particle number emissions varied by a factor of 20. Filament colors had minor effects on emissions compared to other parameters studied.