3D printing safety: fumes, fire protection and children

Highlighted terms are explained briefly when you hover over or tap them.

A 3D printer is a device with a hot nozzle, a hot bed and molten plastic that often runs for hours. That is no reason to worry, but it is a reason to get a few things right. This article covers what research says about emissions and which measures actually help in everyday use.

What gets into the air while printing

Melting filament produces two kinds of emissions:

• Ultrafine particles (UFP): Particles smaller than 100 nanometres. They are so small that they can reach deep into the lungs.
• Volatile organic compounds (VOC): Gases, some of which smell and some of which do not. Depending on the material, these include, for example, styrene with ABS or caprolactam with nylon.

Studies by UL Chemical Insights have detected over 200 different compounds in the emissions of FDM printers. One clear result: ABS releases orders of magnitude more particles and more VOCs than PLA. Higher printing temperatures generally increase emissions.

A study by the Federal Institute for Materials Research and Testing (BAM) commissioned by the German Environment Agency also shows that most particles are produced during the heating phase, after which the rate drops significantly. And filaments of the same base material differ considerably depending on the manufacturer.

The Institute for Occupational Safety and Health of the DGUV (IFA) writes that, according to current knowledge, the guideline values for indoor spaces are met if the room is ventilated regularly and sufficiently and the material is not heated above its decomposition temperature (IFA project 3142). That is no guarantee for every printer and every filament: how much is produced depends heavily on the material, additives, nozzle temperature, machine and ventilation. Long-term health effects have not yet been conclusively researched. So caution is appropriate, panic is not.

Ventilating and filtering

Practical rules:

• Do not run the printer in the bedroom or a child’s room.
• Print ABS, ASA and nylon only with an enclosure and a filter or exhaust air.
• With enclosed printers, wait a few minutes after printing before you open the door.
• Do not print hotter than necessary. You can find the right temperature with a temperature tower, see Printing temperature.
• Prefer filament from known manufacturers with a safety data sheet.

Important: draughts interfere with printing. So ventilate in short bursts rather than leaving a window tilted open directly next to the printer.

Fire protection

Fires caused by 3D printers are rare, but not impossible. The cause is usually defective heaters, loose cables or missing protective functions.

• Thermal protection in the firmware: Current printers switch off the heater if the measured temperature does not respond as expected, for example because a temperature sensor has slipped out. With old machines or self-compiled firmware, check whether this protection is active.
• Smoke detector in the room with the printer. This is inexpensive and sensible.
• Non-flammable surface, with no papers, cardboard boxes or curtains directly next to the machine.
• Check cables, especially at the heated bed. On bed slingers the cable moves constantly with the bed and can break over time.
• No overloaded power strips. The heated bed briefly draws a lot of current while heating up.
• Do not leave long prints running completely unattended. If you are not at home, a camera with remote shut-off helps. Long prints overnight are common, but then only with a smoke detector and a safe location.

Hot parts and moving mechanics

Depending on the material, the nozzle reaches 200 to 300 °C and the print bed 60 to 110 °C. Both stay hot for a while after printing. When doing maintenance work on the nozzle, always wait or wear gloves, see also Maintaining your 3D printer.

Do not reach into a running printer. Belts and axes can trap fingers, and a print head under high acceleration is faster than you can react.

Children and pets

• An enclosed printer protects against reaching inside. With open machines, place the printer out of reach.
• Let children work at the printer only under supervision and stick to PLA, because it has the lowest emissions.
• A child’s room is not a good place to put it.
• Pets are sensitive to fumes, birds especially so. Do not run the printer in the same room.
• Small printed parts and support remnants can be swallowed.

Food contact: better not

Many filaments count as food-safe as a raw material. That does not mean a printed part is. The reasons:

• Layer lines: Food residue and bacteria settle in the fine grooves and can hardly be cleaned reliably.
• Nozzle: Depending on the alloy, brass contains some lead, and brass nozzles wear down. The abrasion ends up in the print.
• Additives: Dyes and additives are often not tested for food contact.
• Cleaning agents can soak into the grooves and leach out again later.

The Prusa Knowledge Base also advises against using prints as food containers. For cookie cutters that have only brief contact, the risk is lower. If you want to go further, you can seal parts with a food-approved epoxy resin. What applies legally and in practice is covered in detail under Food-safe printing.

Sanding carbon and glass fibre filaments

Fibre-reinforced filaments contain short fibres. While printing, they stay bound in the plastic. When sanding, drilling or sawing, however, they are released as fine dust that can irritate skin, eyes and airways.

• Wet-sand rather than dry-sand
• Wear at least an FFP2 mask, preferably FFP3
• Vacuum up the dust, do not blow it away
• Do not work on it in the living area or the kitchen

More on these materials in fibre-reinforced filaments.

Next: Printing ABS, if you want to use a higher-emission material safely.