Filament Fire Test: Which 3D Prints Burn and Which Don't

Setting 3D prints on fire on purpose

Maker's Muse, working with the National Hobby Robot League, torched six filament types to see which ones turn 3D prints into fire hazards. The test was simple: expose PLA, PETG, ABS, ASA, TPU, and PEBA samples to an open flame and watch what happens.

The results

Standard PLA burned readily. It contains enough carbon to act like a candle once lit. One surprise: Prusa Galaxy Black PLA needed a blowtorch to ignite and then burned hot while melting, while Elegoo PLA+ caught fire quickly with a dirty yellow flame. Additives made a bigger difference than the base polymer.

HTPLA, or high-temperature PLA, behaved differently. It self-extinguished almost immediately after the flame was removed. That makes it the safest PLA variant for parts that might see heat.

Black PETG resisted ignition almost entirely. ABS and ASA, by contrast, loved the flame. They burned aggressively with sooty yellow plumes. HIPS acted similarly.

TPU was the clear winner for flame resistance. The blowtorch could not start it burning; it only melted. Foam TPU was the exception. It burned more aggressively than ABS or ASA, which is worth remembering if you use flexible filament for gaskets or dampeners near heat sources.

What this means for your prints

If your part might encounter open flame, high heat, or sparks, PETG and solid TPU are your safest bets. ABS, ASA, and HIPS become fuel. Standard PLA is a fast-burning candle. HTPLA adds a useful safety margin without changing the printing profile too much.

The test also reinforces why infill and wall thickness matter. Denser parts take longer to ignite and burn slower. For functional parts near heat, solid walls and high infill are cheap insurance.