ABS (Acrylonitrile butadiene styrene) is a petroleum-based non-biodegradable plastic. When heated between 210°-250°C for extrusion in a 3D printer, it exudes fumes which are unpleasant to most users. Physical discomfort from these fumes is reported to be on a scale between no discomfort to drowsiness, headaches and nausea.
The MSDS (Material Safety Data Sheet) states "The ABS sheet is not expected to be an inhalation hazard under normal processing conditions. If material is processed under prolonged exposure to flame or high temperature, thermal burns to the skin may occur, and gases may be produced that are irritating to the respiratory systems".
Kendall at Solidoodle Wiki wrote an article entitled ABS Safety. This article states that, "None of the components present in this material are listed as a carcinogen. Under normal processing conditions, this product contains no toxic chemicals." However it also states that, "Fumes produced during the melting processing, may cause eye, skin, and respiratory tract irritation, and if overexposed, could cause nausea and headache."
The general consensus among those using ABS filament in their 3D printers is that it is better to be safe than sorry. Therefore it is recommended that the room in which the 3D printer is operating should be well ventilated or a protective filtering system should be put in place.
Chris Chiang, a biomedical engineer, has written, "I believe that it is very difficult to reach a conclusion on non-acute long-term health effects of anything without a carefully-designed study (that eliminates circumstantial influences, placebo effects, and correlations with other variables). They're expensive, and I don't see one being done on ABS fumes anytime soon. Material Safety Data Sheets typically only seem to draw conclusions on the short-term, more acute effects of exposure. I don't trust that the testing of such examined long-term exposure effects, effects through respiratory exposure, and data of the material being used as it is (extruded and hot, rather than static and cold)."
Chris offers a solution that will eliminate ABS fumes in the absence of outside ventilation. The Fume Chamber which uses a negative-pressure, activated-carbon filtering system can be built for approximately $35.00. Instructions can be found at Thingiverse.com.