Creality K2 Closed Air Recirculation Filter

Creality K2 Closed Air Recirculation Filter (HEPA + Activated Carbon)

This project converts the stock exhaust system of the Creality K2 into a closed-loop air recirculation system designed for printing engineering materials such as ABS, ASA, Nylon, Polycarbonate and other odor-producing filaments.

Instead of exhausting heated chamber air outside the printer, the system continuously circulates it through an activated carbon filter and a HEPA filter, then returns the cleaned air back into the heated chamber. This helps reduce odors, capture ultrafine particles, and maintain a stable chamber temperature during long prints.

Note: This system is designed to reduce odors and airborne particles. It is not a replacement for proper room ventilation when printing engineering materials.

Printing

It is strongly recommended to use the supplied 3MF project. All parts are already oriented and configured for optimal printing on the Creality K2.

The model is designed to be printed from PETG.

PETG is recommended because ABS printing is performed with a heated chamber (approximately 65°C), where PLA may deform over time.

The complete project is divided into three build plates.

Assembly

The assembly combines threaded and glued connections.

Glued parts

• The elbow ducts located on Plate 2 are printed in two halves and must be bonded together using cyanoacrylate (super glue).

• The elbow duct is then glued to the main filter tube.

• The mounting flanges are also glued to the elbow ducts.

Threaded parts

The remaining components are assembled using printed threads.

• The upper filter cap screws onto the filter body.

• The lower elbow duct screws onto the upper duct.

No additional fasteners are required.

Required Hardware

• Round magnets 10 × 2 mm

• Activated carbon filter

• HEPA filter

The HEPA element used in this project is cut from a Hyundai Accent, Getz cabin air filter, trimmed to fit the housing.

Printer Modification

To use this filtration system, a small printer modification is required.

Remove the rear cover and reverse the lower exhaust fan, so it blows filtered air back into the chamber instead of exhausting it outside.

The airflow becomes:

Heated chamber → Upper exhaust fan → Activated carbon filter → HEPA filter → Lower fan → Heated chamber

This creates a continuous closed-loop filtration system while preserving the chamber temperature.

Recommended Slicer Settings

For ABS printing I use the following settings:

• Rear exhaust fan: Enabled

• Fan speed: 60%

These settings keep the upper fan running continuously during printing, ensuring constant air circulation through the filter.

Sealing Recommendation

For the best performance, I recommend sealing the gap between the printer's rear panel and the fan housing using self-adhesive foam weather stripping.

This minimizes hot air leakage, improves filtration efficiency, and prevents untreated chamber air from bypassing the filter.

Switchable Operating Mode

One of the key features of this design is its switchable operating mode.

The filter housing is attached to the printer using magnets, allowing it to be quickly moved between two positions without any tools.

Filtration Mode

When the filter is raised, the air ducts are aligned with the printer exhaust system.

The printer operates in a closed-loop air recirculation mode, where chamber air continuously passes through the activated carbon and HEPA filters before returning back into the chamber.

This mode is recommended for:

• ABS

• ASA

• Nylon

• Polycarbonate

• Other engineering materials producing odors or ultrafine particles.

Standard Ventilation Mode

When printing PLA, PETG, TPU or other low-odor materials, the filter can simply be lowered.

In this position, a steel cover seals the filter housing, preventing unnecessary airflow through the activated carbon filter. This significantly extends the service life of the carbon media since it is not continuously exposed to ambient air.

With the filter lowered, the rear exhaust fan operates as originally designed, allowing fresh room air to enter the printer and warm air to exit the chamber when required.

🇺🇸 Internal Air Diffuser

The project also includes a replacement internal air diffuser, which replaces the factory cover inside the printer.

The diffuser is printed from ABS, as it operates inside a heated chamber that can reach 70°C.

Its purpose is to redirect the filtered airflow away from the printed part. Instead of blowing directly toward the build plate, the diffuser guides the airflow toward the right side wall and downward, maintaining efficient air circulation while preventing unwanted cooling of temperature-sensitive prints such as ABS or ASA.

Diffuser Assembly

For improved print quality and to minimize the need for supports, the diffuser is split into multiple printable parts.

Some components, including the locking clip, must be bonded together using cyanoacrylate (super glue) after printing.

Once assembled, the diffuser installs in place of the original factory cover.