Bambu Lab AMS 2 Pro Humidity Stuck at 30%? What to Check First

By Lee Zhong, GrandCube3D

Your Bambu Lab AMS 2 Pro has finished drying, but the display still reads around 30% humidity. Before starting another cycle, check the step that follows heated drying: restoring an effective dry-storage setup.

If you removed the desiccant for drying, put fresh or properly regenerated desiccant back into suitable holders once it is safe to handle the chamber. Replace spent material, close the lid properly, and assess the humidity trend after the temperature settles. If effective, compatible desiccant stayed inside throughout the cycle, there is no need to remove and reinstall it just to complete this routine.

The aim is to keep the prepared filament in a suitably dry environment between prints. This checklist focuses on what to do after drying. For the explanation of cooling and humidity rebound, read Why Does AMS 2 Pro Humidity Rise After Drying?.

Restore effective desiccant before judging the storage result

A completed filament cycle does not establish that the desiccant is ready for another storage period. Check the material you actually have: is it fresh, properly regenerated, or already carrying moisture from previous use?

Bambu Lab's filament guidance recommends sealed storage with effective desiccant after drying. The following routine puts that advice into practice; it is a storage checklist, rather than a requirement to remove desiccant for every cycle. Bambu Lab: filament drying and storage guidance.

1. Have a fresh or correctly regenerated refill ready. Follow the desiccant supplier's regeneration and cooling instructions, and keep the prepared refill sealed until use.
2. Follow the equipment's cooldown instructions. When it is safe to open the chamber, return any removed desiccant or replace spent material, then close it promptly.
3. Remove any sealed outer transport wrapper intended to be removed before use. Leave the working, breathable sachet intact; loose beads belong in an appropriate closed holder.
4. Check that holders are secured and leave the spools, rollers, filament path and air passages clear.

Use the indicator instructions for your particular desiccant. Different formulations use different colors, and a full-looking holder can still contain spent material. Follow the temperature limits of both the refill and the holder if either will remain inside during a later drying cycle.

Close the chamber and establish a room-temperature baseline

After installing the refill, check the lid edge and seal for trapped objects, displaced sections or anything preventing normal closure. Engage the lid locks as intended.

Keep the chamber closed while its temperature settles, then record the temperature and RH together. Take later readings under similar conditions without repeatedly opening the lid to inspect it. There is no fixed waiting time that fits every load and room.

An RH reading describes chamber air, not the water content inside a spool. Bambu Lab also explains that cooling can raise the displayed percentage. Compare the settled storage trend with your filament's storage requirements; 30% is a troubleshooting starting point, not a universal pass/fail threshold. Bambu Lab: humidity readings and checks.

Use the trend to choose your next step

These observations help narrow the checks. They do not measure filament moisture or certify that the enclosure is leak-free.

Add capacity when the existing effective refill does not last

Restoring effective desiccant comes first. Increasing its amount is a separate decision.

Desiccant has a finite moisture capacity, and it works best within a suitably closed enclosure. A large quantity that is already saturated has little useful reserve left. AGM Container Controls: desiccant capacity and enclosure conditions.

Consider additional capacity when a fresh refill brings humidity under control, the chamber closes correctly, and the refill still needs servicing more often than suits your routine. Check continuing moisture sources first. More effective material may provide a larger reserve under comparable conditions; the result depends on the refill, enclosure, room and use pattern.

Start with the amount supported by your chosen holders. If you add more, record the dry fill mass and change one part of the setup at a time. Compare how long it maintains the required storage conditions at similar temperatures and with similar lid-opening habits. This is more useful than chasing the lowest reading immediately after an installation.

A suitable spool-core canister or chamber holder can make room for that reserve and simplify refilling. Choose accessible fill openings, secure bead containment and verified operating clearance. Extra capacity should remain easy to inspect and service, with the AMS air passages unobstructed.

If it still stays high, separate the spool from the chamber

For a simple comparison, keep removed spools in suitable sealed storage and observe the closed AMS with the same known-effective desiccant at a similar room temperature. Then compare it with the loaded setup. A difference gives you a reason to investigate the load; it does not identify the exact moisture source on its own.

Also review whether the completed cycle suited the exact filament and spool. Prusa's guidance distinguishes protected storage from active drying and recommends matching the equipment to the material's drying temperature. A dry-storage refill cannot be assumed to complete an inadequate filament-drying process on your printing schedule. Prusa: drying filament.

If heating appears ineffective, check the actual temperature, selected material, power arrangement and unobstructed air passages against Bambu Lab's instructions. AMS 2 Pro uses controlled intake and exhaust during drying; moisture has a route out of the chamber. When drying is off, those ports close for storage. Avoid blocking them to force a lower reading. Bambu Lab: AMS 2 Pro drying workflow.

Frequently asked questions

Should I remove desiccant before every drying cycle?

This checklist does not require that. Follow the instructions and temperature limits for the desiccant and its holder. If you remove it, restore an effective refill for subsequent storage. If it remains effective and compatible inside, leave it in place.

Will adding desiccant guarantee a reading below 10% or 0%?

There is no guaranteed reading from adding a particular quantity. Judge the setup by its ability to maintain the conditions required by your material, alongside appropriate filament preparation.

Does another heated cycle regenerate the refill?

Do not assume that a filament preset completes the regeneration procedure for your desiccant. Use the refill supplier's specified process and check the holder's heat limits separately.

For your next drying session, prepare the storage refill as well as the filament. Finish the appropriate drying process, restore effective desiccant where needed, close the chamber, and check whether its settled humidity remains suitable for storage.

Related reading

• Does the Bambu Lab AMS 2 Pro Still Need Desiccant?
• Why Does AMS 2 Pro Humidity Rise After Drying?
• When Should You Replace Desiccant in Your Bambu Lab AMS?