Voron V2.4 Exhaust Filter Mod — Better Air Filtration for ABS Printing

Mod V2.4 Filtration

Printing ABS and ASA on a Voron V2.4 generates volatile organic compounds (VOCs) and ultrafine particles (UFPs) that you don't want recirculating in your living space. The stock V2.4 has no dedicated filtration system — you're expected to either vent outdoors or add a filter mod. This guide covers every popular exhaust and recirculation filter mod for the V2.4, from the community-favorite Nevermore to ducted CPAP setups and high-end HEPA+carbon combinations. Last updated: May 2025.

We'll cover the pros and cons of each approach, what printed parts you need, recommended fans and filter media, and how to integrate the mod with your Klipper configuration for automatic chamber filtering during and after prints.

Why You Need Filtration on a V2.4

Unlike the Trident which has a built-in exhaust port in the deck plate, the V2.4 was designed as a showpiece — an open-frame design enclosed by users with custom panels. The original spec didn't include any exhaust or filtration. This means:

• VOC buildup: ABS emits styrene and other VOCs that accumulate in the enclosure. High concentrations can cause headaches and respiratory irritation over time.
• UFP accumulation: Nanoparticles from molten plastic stay suspended in the chamber air for hours after a print finishes.
• Print quality impact: Stale, VOC-heavy air can affect layer adhesion and increase the chance of delamination on tall parts.
• Odor: Even if you don't mind the smell, your housemates/neighbors probably do.

Adding a filter mod improves air quality, reduces odor, and can actually improve print consistency by ensuring the chamber atmosphere remains stable during long prints.

Option 1: Nevermore Filter (Carbon Recirculation)

The Nevermore is the most popular filter mod in the Voron community. It's a recirculation filter, not an exhaust filter — it sits inside the chamber and pulls air through activated carbon to adsorb VOCs, then blows clean air back into the chamber. It does nothing for heat extraction or UFP removal (carbon doesn't filter particles), but it's excellent at eliminating ABS odor.

Nevermore Variants for V2.4

• Nevermore Micro: Small single-fan unit. Fits in the V2.4 rear panel space near the Z belts. Uses one 4020 or 5015 fan and a single carbon bed. Adequate for a single printer in a well-ventilated room.
• Nevermore 5 Duo: Dual 5015 fan unit with two carbon beds. Significantly higher CFM and carbon volume. Recommended if you print multiple ABS parts back-to-back.
• Nevermore 6: The latest revision with optimized airflow channels and a single 6020 fan. Quieter than the Duo with similar flow rate. Uses a larger carbon bed that lasts longer between refills.

Printed Parts Required

All Nevermore variants require printed PETG or ABS parts for the housing, fan brackets, and carbon tray. You can find the STLs on the Nevermore GitHub. Print in ABS for best heat resistance — the chamber can reach 50-60C during long V2.4 prints.

Filter Media

• Activated carbon pellets: 4mm mesh size, coconut-shell based. Avoid dust-grade carbon — it clogs quickly and bypasses into the chamber.
• Carbon pads: Pre-formed 3mm thick carbon pads that fit the Nevermore trays. Easier to replace but less surface area than loose pellets.
• Refill frequency: Every 200-300 print hours, or when you notice ABS smell returning.

Option 2: BentoBox Filter (HEPA + Carbon)

The BentoBox is a combined HEPA + carbon recirculation filter, originally designed by the Voron community for the V0 but adapted for the V2.4. Unlike the Nevermore which only handles VOCs, the BentoBox also captures UFPs and smoke particles through its HEPA stage, then polishes the air through a carbon stage.

BentoBox on V2.4

On a V2.4, the BentoBox mounts to the rear extrusion or the deck plate. It uses a 6020 or 6030 axial fan pulling air through a HEPA H13 filter (same standard as room air purifiers), then through a carbon bed. The dual-stage filtration means the air coming out of the box is genuinely clean — both VOC-free and particle-free.

• Pros: Filters both VOCs and UFPs. HEPA media is cheap and standardized (buy generic H13 vacuum cleaner filters). The box is printable without needing non-printed parts beyond the fan and filter media.
• Cons: Larger footprint than the Nevermore. The axial fan runs continuously during prints. HEPA filters add backpressure that reduces throughput compared to a carbon-only recirculation filter.
• Recommended fan: Sunon MF60201V2 or Delta AFB0624 — 60x60x20mm axial, 24V, PWM controllable.

Option 3: CPAP Ducted Exhaust with External Filtration

For the ultimate filtration setup, many V2.4 builders use a CPAP fan-based ducted exhaust that vents the chamber air outside — either directly through a window or through an inline carbon filter. This is the same approach used in professional ABS printing labs and is the most effective way to remove both VOCs and UFPs.

How It Works

A CPAP blower (typically a DHFOP 24V dual-ball bearing fan, ~$15-20 on AliExpress) is mounted to the V2.4 rear or top panel. A 4-inch flexible duct runs from the blower to a window vent adapter or through-wall exhaust. Optionally, an inline carbon filter can be placed in the duct path to adsorb VOCs before the air exits.

• CPAP blower: DHFOP or similar, ~2.5-3 CFM at 24V. PWM controllable. Near-silent at low speeds.
• Duct: 4-inch flexible aluminum or PVC duct. Keep runs under 10 feet for minimal backpressure.
• Inline filter: 4-inch carbon pre-filter (grow tent style, ~$10). Replace every 500-1000 print hours.
• Window vent: Adjustable window seal with 4-inch port, ~$15 on Amazon or AliExpress.

Klipper Integration

Wire the CPAP fan to a MOSFET or PWM-capable fan port on your controller board. Add a macro to Mainsail/Fluidd that lets you toggle the exhaust fan at different speeds:

# In printer.cfg
[output_pin exhaust_fan]
pin: PA6       # Adjust to your board pin
pwm: True
cycle_time: 0.01
hardware_pwm: False
value: 0

[gcode_macro EXHAUST_ON]
gcode:
  SET_PIN PIN=exhaust_fan VALUE=255  # 100%

[gcode_macro EXHAUST_OFF]
gcode:
  SET_PIN PIN=exhaust_fan VALUE=0    # 0%
    

Option 4: Hepa + Carbon External Box (Standalone)

If you don't want to modify your V2.4 panels, consider a standalone filter box that sits next to the printer. Commercial units like the Nevermore Double (yes, Nevermore makes an external version) or a DIY 4-inch duct carbon box with a computer fan work well. The external box pulls air from the chamber via a duct, filters it, and returns it to the room.

This is the least invasive option and works for apartment dwellers who can't cut holes in walls or windows. It's also the easiest to maintain — the filter box is outside the printer, so you don't need to open the enclosure to swap media.

Comparison Table

Installation Tips for V2.4

• Mounting location: The rear panel area (behind the Z motor mounts) is the most common mounting spot for Nevermore and BentoBox on V2.4. Use the unused M3 threaded holes in the 2020 extrusions.
• Panel clearance: If you're using a deck panel with top-hat mounting, verify the filter module clears the Z chain and the bed carriage at maximum Z height.
• Wiring: Route power and PWM wires along the existing cable chain path on the rear of the printer. Use a 2-pin JST-XH or Molex Micro-Fit connector so you can easily disconnect the filter module when servicing the printer.
• Filter orientation: For carbon recirculation filters, ensure the airflow direction pulls air through the carbon bed — push-through configurations create channeling and reduce contact time.
• CPAP duct sealing: Use aluminum tape (not duct tape, which degrades at chamber temperatures) on all CPAP duct joints. A leak in the duct under positive pressure will push unfiltered air into the room.

Macro Integration: Automatic Filter Control

Tie your filter to the Klipper print state using a [delayed_gcode] that runs the filter for a set time after each print finishes:

[delayed_gcode post_print_purge]
initial_duration: 0
gcode:
  # Turn exhaust fan on to 80% after print
  SET_PIN PIN=exhaust_fan VALUE=204
  # Turn Nevermore on full
  SET_PIN PIN=nevermore_fan VALUE=255
  # Wait 10 minutes
  G4 P600000
  # Turn everything off
  SET_PIN PIN=exhaust_fan VALUE=0
  SET_PIN PIN=nevermore_fan VALUE=0

[gcode_macro END_PRINT]
gcode:
  {% if printer.print_stats.state == "printing" %}
    # ... your existing end print macro ...
    UPDATE_DELAYED_GCODE ID=post_print_purge DURATION=1
  {% endif %}
    

This runs the filter for 10 minutes after each print, clearing remaining VOCs and particles from the chamber before you open the door to retrieve the part.

Filter Media Sourcing

China-direct tip: Coconut-shell activated carbon 4mm pellets are available on AliExpress for $3-5 per kilogram, compared to $15-20 from specialty 3D printing vendors. Look for "4mm coconut activated carbon pellets aquarium filter" — it's the same product without the 3D printing markup. HEPA H13 filter media sheets (50x50cm) are $2-3 each on AliExpress. Stock up for the year at a fraction of the cost.

For Nevermore users, buy the pre-cut carbon pads from the Nevermore store or cut your own from 3mm thick activated carbon felt sheets. The felt is less dusty than loose pellets and easier to handle during changes.

Final Recommendations

• Best for odor elimination: Nevermore 5 Duo or Nevermore 6 — simple, effective, cheap, and well-documented.
• Best for health/UFPs: BentoBox with HEPA + carbon — the only recirculation option that actually filters particles.
• Best for total air quality: CPAP ducted exhaust with outdoor venting — nothing beats actually moving the bad air outside.
• Best for apartments: External filter box + Nevermore — no structural modifications needed, and you can take it with you when you move.

Most V2.4 owners start with a Nevermore and later add a ducted CPAP exhaust if they need more aggressive filtering. Whichever route you choose, adding filtration is one of the highest-impact quality-of-life mods you can make for your V2.4. Your lungs and your housemates will thank you.