Are ABS/ASA fumes dangerous, and do I need ventilation?

Print ABS and ASA only where the room is ventilated, and do not aim that airflow at the part. Prusa calls the fumes potentially dangerous and names styrene for both plastics. A chamber study measured styrene from ABS and HIPS and told operators to be careful in a small, poorly ventilated office, or to use combined gas and particle filtration. ABS printing, ASA printing, enclosures, and warping are the print-process pages. Heat is why people choose these filaments anyway.

What is published

Prusa's ABS article lists toxic fumes as a main disadvantage and "potentially dangerous fumes (styrene)" in the cons table. The instruction is a well-ventilated room, because the material releases fumes and substances that could pose a potential health risk, and no draft around the print. Prusa's ASA article uses the same pair of sentences and the same styrene cons line. It also says ASA does not smell as much as ABS. Smell is not the measurement.

Azimi, Zhao, Pouzet, Crain, and Stephens, Environmental Science & Technology, 2016, DOI 10.1021/acs.est.5b04983, measured desktop printers in a chamber. The abstract's median ultrafine-particle emission rates ran from about 10^8 to about 10^11 per minute, varying mostly by filament. The largest VOC lines include styrene from ABS and HIPS at about 10 to about 110 micrograms per minute, caprolactam from nylon and from imitation wood and brick at about 2 to about 180 micrograms per minute, and lactide from PLA at about 4 to about 5 micrograms per minute. The screening line says use caution with many of those combinations in a poorly ventilated small office, or without combined gas and particle filtration. This page does not convert those rates into a room concentration, and it does not cite an occupational exposure limit.

Bambu ABS and PolyLite ABS both list 230–260 °C (446–500 °F) and a bed of 90–110 °C (194–230 °F). Prusament ASA lists 250–270 °C (482–518 °F) and 100–120 °C (212–248 °F). Those are print temperatures. A separate ABS or ASA safety data sheet was not retrieved, so this page does not quote an SDS section. ABS and ASA are the hubs.

The threads

r/prusa3d 108oby3 is someone printing PLA in a bedroom with a window, a ceiling fan, and an Ikea purifier. The score-20 comment says that monitor is PM2.5 only and will not detect VOCs. That is the same split the paper makes between particles and gases.

r/BambuLab 1vj3wsm is the ABS/ASA fume question. The score-3 comment exhausts outside and says the absence of a smell is not a safety result. The score-2 comment's 7 kW fan and 60 m3/h rating describe that cupboard. They are not a specification for your printer.

r/3Dprinting 1qrp6el drew a score-60 comment that PLA is corn starch based. PLA's lactide number above is the published comparison. The comment is not.

Questions