Foaming TPU Burns More Aggressively Than Any Other 3D Printing Filament, Test Shows

Maker's Muse Burn Test Exposes Filament Fire Risks

Not all 3D printing filaments behave the same way when they meet an open flame. A recent burn test by Maker's Muse put the most common materials through a deliberate fire exposure, and the results should change how you shop for filament if you print in a home workshop or garage.

The test exposed PLA, PETG, ABS, ASA, TPU, PEBA, HIPS, and HTPLA to both an open flame and a blowtorch. Standard PLA burned readily, which most experienced printers already know. Black PETG resisted ignition, and regular TPU did not catch fire even under direct torch exposure.

The surprise was foamed TPU. The lightweight, expanded version of the flexible filament burned far more aggressively than standard TPU and even outpaced ABS and ASA in flame intensity. The test footage shows a small sample producing a tall, active flame that continued burning until the sample was consumed.

Foam TPU is popular for lightweight functional parts, cosplay props, and vibration damping. It prints easily and feels light in use. The burn test suggests those same properties create a serious fire hazard if the part sits near a heat source, electronic enclosure, or heated bed left running unattended.

What the Data Says About Each Material

PETG and regular TPU are the safest common options for environments where fire risk matters. Both resist ignition well. PETG is rigid and structurally useful for enclosures, brackets, and mechanical parts. TPU is flexible and great for gaskets, dampers, and protective covers.

ABS and ASA burn readily with a sooty yellow flame. HIPS behaves similarly. These are not materials you want near open flames or hot electronics. HTPLA, a high-temperature variant of PLA, self-extinguished after torch exposure in the test, which makes it a safer PLA alternative if you need rigidity and heat resistance.

PEBA, another flexible filament, burned low and slow according to a separate Maker's Muse test. It did not explode into flame like foamed TPU, but it sustained combustion for an unusually long time.

Workshop Safety Takeaways

The simplest rule from this test is to keep foamed TPU away from heat sources. That means leaving printed foam TPU parts clear of heated beds, hotend fans, and electrical enclosures that run warm. If you store spools, keep them in a sealed container away from direct sunlight and heat.

Ventilation matters too. Burning any thermoplastic releases hazardous gases. TPU fumes include cyanide compounds. PETG emits caprolactam. A room with a working 3D printer should have active ventilation regardless of material, but the consequences of a fire go up dramatically with foamed TPU in the mix.

For functional parts that need to be lightweight, PETG is the better fire-safe choice when rigidity works. When you need flexibility, regular TPU is safer than the foamed version. The weight savings from foamed TPU are real, but they come with a fire risk that most users never see until a test like this makes it visible.