What humidity should filament be stored at?

Use a product-specific storage target and measure inside the container you are judging.

By the Filament Drying Lab team · Checked 2026-10-25

Look for a storage humidity target in the filament maker's documentation. There isn't one number here that certifies every material as dry.

A documented benchmark

Bambu Lab's ASA Aero technical sheet specifies below 20% RH in sealed storage with desiccant. This is a useful example of a published requirement; it isn't a universal promise for other products. Source: Bambu Lab ASA Aero TDS, checked 25 October 2026.

For your spool, check its own current sheet and use that target when monitoring the box.

Measure the relevant air

A room hygrometer and a sensor inside a sealed box describe different places. Label the readings so you don't compare a workshop measurement with a storage target as though they were the same environment.

The reading also changes with temperature. Note both values if you want to understand a pattern rather than a single moment. Source: National Weather Service, checked 25 October 2026.

What a low reading doesn't prove

A low box reading does not directly measure moisture inside a spool. If the filament requires drying, complete the prescribed cycle first. Use storage to protect that work afterwards.

The humidity calculator estimates dew point from air conditions. It cannot tell you how many hours a particular filament has left before its print quality changes.