Today, I spent some time exploring how to build a more effective ventilation and exhaust system. After going through several reference designs and resources, I realized that simply ventilating a sealed space isn’t enough to reduce absolute humidity. To truly remove moisture from both the filament and the internal environment, you need a dedicated drying mechanism – one that can actively absorb water from the air.
Based on the suggestions I got from ChatGPT, it turns out that instead of building a complex ventilation and drying duct system, a simpler and more efficient solution is to place a dehumidifier or drying unit directly inside the sealed space. This approach not only reduces structural complexity but also offers more stable and controllable drying performance.
So, I decided to run a simple verification test. The first objective was to confirm whether the thermostat (SONOFF TH Elite THR316D) could maintain the temperature around a set target. The second goal was to test whether combining desiccant packs with internal air circulation could effectively absorb moisture and lower the absolute humidity inside the sealed container.
I took several packs of desiccant from my old AMS unit and placed them inside the sealed container. Then, I installed a PTC heating module inside, controlled by the TH Elite thermostat. The thermostat was configured to turn on the PTC when the temperature dropped below 49°C, and shut it off when it exceeded 50°C – keeping the system hovering around that temperature. I specifically chose the 50°C threshold for a reason: After researching silica gel properties, I found that its optimal working range is between -40°C and 50°C. Above 50°C, its absorption efficiency drops, and over 80°C, it may even release previously absorbed moisture.
So setting the drying environment to stay near 50°C helps keep the desiccant performing at its best.
In addition, I added a continuously running circulation fan inside the box.
Even when the PTC and its cooling fan shut off, this circulation fan continues running – ensuring constant airflow across the desiccant packs for improved moisture absorption.
Before powering on the system, I took an initial measurement: The sealed container had a temperature of 28.1°C and a relative humidity of 51.6%. Based on this, the calculated absolute humidity is approximately 14.12 g/m³, which means the 5L container holds roughly 0.0706 grams of water in total.
After about 10 minutes of heating, I made the first observation: The temperature had reached 50.6°C, and the relative humidity dropped to 12%. Using the same formula, the absolute humidity at this point was approximately 10.27 g/m³,
which means the 5L container now held about 0.0514 grams of water—a reduction of roughly 27%.
An hour later, I checked again. The temperature remained steady at 51°C,
while the relative humidity had dropped further to just 5.3%. According to the same calculation, the absolute humidity was now approximately 4.62 g/m³,
which means there was only about 0.0231 grams of water remaining in the 5L sealed container. Compared to the previous reading just an hour ago, this was another 55% drop in water content.
Two hours into the test, I took one final reading. At a temperature of 50.7°C, the relative humidity had dropped further to just 3.5%. Using the same calculation method, the absolute humidity was now approximately 3.00 g/m³, which means there was only about 0.0150 grams of water remaining in the 5L sealed container.
I also recorded a 2-hour time-lapse video, capturing the TH Elite display at one frame every 5 seconds. The final video is about 20 seconds long, clearly showing the temperature and humidity changes over time. From the footage, I could see that the temperature fluctuated between 48°C and 52.8°C, meaning the system maintained a controlled range of approximately 48–53°C under the current settings.
After one hour of continuous ventilation and desiccant absorption,
the absolute humidity inside the 5L container dropped by around 70%—a very noticeable improvement. It looks like this setup is not only functional, but also quite effective. Compared to the previous data point, this marks another 33% drop, bringing the total reduction to about 78% from the initial value.
At 3.00 g/m³, the air inside the container is now extremely dry.
After completing the drying phase, I turned off the TH Elite’s automatic control mode and powered down the PTC. Only the internal circulation fan was left running to keep the air moving inside the sealed container. Thirty minutes later, once the temperature had dropped and stabilized, I performed one final reading to evaluate post-drying conditions.
To my surprise, I noticed that as the PTC stopped and the temperature started to drop, the humidity reading on the TH Elite continued to decrease instead of rising. Eventually, it even dropped to 0%, which was honestly hard to believe. To verify whether this was accurate or just a sensor quirk, I turned off the internal circulation fan as well and let the system continue to cool. I wanted to see if the humidity would bounce back as the air became less dynamic.
After waiting another 30 minutes, the system reached its final stable state.
The temperature inside the sealed container settled at 29°C, while the ambient temperature outside was about 28.8°C. Surprisingly, the relative humidity reading still remained at 0%.
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