ASA and ABS: smell and fumes when printing, carbon filter and ventilation without ruining the part

Symptom

When printing ASA or ABS the room smells strongly of plastic, you feel discomfort or you are worried about breathing the fumes; or, when you ventilate to get rid of the smell, the parts start to warp or crack.

Likely causes, from most to least likely

1. At printing temperature, ABS and ASA release gases such as styrene, which can be toxic and cause dizziness or nausea (Bambu Lab). Elegoo ranks ABS as the strongest smelling and ASA slightly below it.
2. An open printer or an unventilated room: the gases stay where you are.
3. A spent activated carbon filter: Bambu Lab replaces it every 1,440 printing hours (about 60 days) on its printers with a filter, and Creality every three months on the K1C at about 8 hours of use a day.
4. A filter fan set too low: on the X1E, Bambu Lab explains that without negative pressure in the case the gases escape through the gaps instead of going through the filter.
5. Ventilating by opening the printer or with draughts on the part: ASA and ABS warp or crack if they cool quickly, which is why Prusa asks you to ventilate the room without creating draughts around the part.

Checks to tell which one it is

• Check whether your printer has an activated carbon filter and how many printing hours it has done since the last change.
• Check in the filament profile whether filtering or extraction is enabled and at what speed.
• Look at where the printer is: a bedroom, a living room or a room where you spend many hours.
• Check whether children, pregnant women or people with asthma or breathing problems are nearby.

Before you start

Before taking anything apart, cleaning or adjusting it, switch the printer off and unplug it, unless a step says otherwise, and do not touch the nozzle, the heater block or the bed until they have cooled down. If in any doubt about electricity, heat or moving parts, stop and ask a professional.

Step-by-step fix

1. Where to print

   Print ASA and ABS in an enclosed printer, in a well-ventilated room, and avoid printing them for long periods in bedrooms or living rooms (Bambu Lab). If children, pregnant women or people with asthma or breathing problems are around, ventilate more or do not print these materials.

   Check: The smell does not build up in the room.

   If that does not fix it: Check the printer's filter (next step).

2. A carbon filter that is up to date

   If your printer has an activated carbon filter, replace it when due: Bambu Lab every 1,440 printing hours (about 60 days); Creality every three months on the K1C at about 8 hours a day, or every month if it works as a production machine. On the X1E, at 8 hours a day, the cartridge lasts one month with ABS or PETG versus three with PLA.

   Check: The smell drops during the print.

   If that does not fix it: Adjust the filter fan (next step).

3. Filtering or extraction switched on

   Enable filtering or the exhaust fan in the filament profile if your printer allows it. On the X1E, Bambu Lab sets it at 70% by default and warns: too low and the gases escape through the gaps; too high and the air passes so fast that it filters worse. Do not leave the filter running with the printer idle for long: it wears out.

   Check: No smell comes out of the printer's seams.

   If that does not fix it: Ventilate the room (next step).

4. Ventilate the room without draughts on the part

   Ventilate the room, but without the air hitting the part: Prusa warns that a draught ruins the result. Keep the printer's door and lid closed while printing. For long jobs, Bambu Lab advises a mask with a vapour filter, such as activated carbon ones.

   Check: There is no smell and the parts do not warp or crack.

   If that does not fix it: If your printer is open, see the next step.

5. If your printer is open

   For ASA and ABS, Prusa considers that an enclosure may be needed (essential for large ASA parts): it can also carry a filter and stops children or pets from touching hot parts. If you build it yourself, keep the power supply outside: Prusa warns that inside it would exceed its operating temperature.

   Check: You print without smell in the room and without warped parts.

   If that does not fix it: If you can neither ventilate nor enclose, print that part in a lower-odour material such as PETG or PLA (Elegoo).

6. Clean off the fume residue

   Switch off and unplug the printer before cleaning inside it. ASA and ABS vapours settle on the glass, the door and the rods: Bambu Lab suggests cleaning every 5 spools (5 kg) of these materials, and Creality checking the X axis every 300 hours and cleaning it every 5 kg if you use ABS or ASA.

   Check: The glass is clean and the axes move smoothly.

   If that does not fix it: If an axis still feels stiff after cleaning, check your printer's maintenance guide.

Prevention

• Print ASA and ABS enclosed, in a ventilated room and away from where you sleep or spend the day.
• Log printing hours so you change the carbon filter on time.
• If the part does not need ASA's or ABS's heat or weather resistance, use a lower-odour material.

Still not fixed?

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Printers it applies to

Any FDM (filament) 3D printer, from any brand.

Materials: ASA and ABS.

Official sources

This guide summarises the official documentation linked here:

• ABS / ASA / PC Usage Guide (safety and filters) · Bambu Lab
• X1E air filtration setting guide · Bambu Lab
• K1C/K1C 2025 Maintenance Tips (activated carbon air filter) · Creality
• ASA (material guide) · Prusa Research
• Enclosure guidepost · Prusa Research
• Guide to FDM Printing Filament (odour) · Elegoo