Room Dimensions

Room length

Measure wall to wall

Room width

Ceiling height

Material & Laser

Primary material

Laser type

Higher wattage = more material vaporized = more fumes

Enclosed or open laser?

Enclosed Glowforge, xTool S1, etc.

Open-frame Ortur, Sculpfun S30, etc.

Duct Run

Duct diameter

Match your fan outlet size. Larger = less friction loss.

Duct length

90° bends

45° bends

Never laser-cut PVC, vinyl, or ABS

These materials release chlorine gas (HCl) and hydrogen cyanide (HCN) when burned. No amount of ventilation makes them safe. They will also damage your laser optics and corrode internal components. See our Safety Guide for the full list of materials to avoid.

Ventilation Results

Fill in room dimensions and click
Calculate to see results

You Need

CFM fan rating

Room volume 0 ft³

Air changes needed 0 /hr

Base CFM required 0

After material adjustment 0

After laser type adjustment 0

After enclosure adjustment 0

Duct loss factor 1.00×

Final fan rating needed 0 CFM

How CFM is calculated

CFM stands for Cubic Feet per Minute — the volume of air a fan can move. For laser fume extraction, the goal is to replace contaminated room air with fresh air fast enough to keep particulate and VOC concentrations below harmful levels.

The core formula is based on Air Changes per Hour (ACH) — how many times per hour the entire room volume should be completely replaced:

// Core ventilation formula
CFM = (Room Volume in ft³ × ACH) / 60

// Where ACH depends on material hazard level:
Wood/Plywood: 15–20 ACH
MDF/Particle Board: 25–30 ACH (formaldehyde)
Acrylic: 20–25 ACH
Leather: 20–25 ACH
Rubber: 25–30 ACH
Fabric/Felt: 12–15 ACH
Paper/Cardboard: 10–12 ACH
Coated materials: 25–30 ACH
Stone/Slate: 10–15 ACH
Metal marking: 12–15 ACH

This calculator then applies multipliers for material toxicity (MDF and rubber get a 1.3× boost due to hazardous off-gassing), laser wattage (higher power vaporizes more material per second), and enclosure status (open-frame lasers need 1.3× more room ventilation than enclosed machines).

Why material matters

Not all fumes are equal. MDF and particle board contain formaldehyde-based resins that release formaldehyde gas when heated — a known carcinogen at sustained exposure levels. Acrylic (PMMA) produces methyl methacrylate (MMA) vapor and trace amounts of hydrogen cyanide. Rubber off-gasses sulfur compounds and PAHs. Even natural wood produces fine particulate matter (PM2.5) and carbon monoxide.

The ACH values in this calculator reflect these differences: materials with known toxic byproducts require faster air replacement rates.

Duct sizing tips

Bigger ducts = less friction = more airflow. A 6-inch duct moves significantly more air than a 4-inch duct at the same fan speed.
Never reduce duct diameter below your fan outlet. If your fan has a 6-inch outlet, use 6-inch duct throughout the run. Reducing to 4 inches creates a bottleneck that dramatically increases back pressure.
Keep runs short and straight. Every 90-degree bend adds equivalent friction of 5–10 feet of straight duct (depending on diameter). Two 45-degree bends are better than one 90-degree bend.
Use smooth rigid duct over flex duct. The corrugated interior of flex duct creates 2–3× more friction than smooth metal duct. If you must use flex, keep it as short and straight as possible.

HEPA vs Carbon filters

HEPA filters catch particulate matter down to 0.3 microns — this handles the visible smoke, soot, and fine dust that laser cutting produces. Activated carbon filters absorb volatile organic compounds (VOCs) and odors — the chemical gases you can smell but not see.

For laser fume extraction, you need both. A HEPA filter alone won't stop formaldehyde or MMA vapor from MDF or acrylic. A carbon filter alone won't stop fine particulate from wood or leather. Most quality inline filter units combine both stages.

Sources: ACH values are derived from OSHA general industry ventilation guidelines (29 CFR 1910.94) and the ACGIH Industrial Ventilation: A Manual of Recommended Practice. Specific ACH ranges reflect the contaminant generation rates typical of desktop laser engraving at the wattages common in hobbyist and small-business settings.