If you machine tight-tolerance parts, you already know the frustration: the shop floor meets production needs, but measuring those parts in a dust-laden corner fails CMM checks. Traditionally there were two choices: ship parts to an external lab (delays) or spend six figures on a dedicated cleanroom (budget shock).
A third option exists—and it’s gaining traction with contract manufacturers and quality managers: fan-filter units (FFUs). In this post we’ll explain how FFUs turn any spare floor space into an ISO-class clean zone for inspection or light assembly, often in a single weekend and at a fraction of a hard-wall cleanroom’s cost. All examples reference the Aeroex Air-Fit FFU, but the principles apply to any high-quality unit.
1 | What is a fan-filter unit?
An FFU combines a motorized fan with a high-efficiency particulate air (HEPA) or ultra-low penetration air (ULPA) filter inside a self-contained housing. Think of it as a “drop-in ceiling tile” that pulls contaminated ambient air through the filter and pushes ISO-class air straight into your work zone.
Key components
- EC Fan or motorized impeller – Provides uniform, downward laminar flow.
- Pre-filter – Captures bulk dust; extends HEPA life.
- HEPA/ULPA filter – Typical 99.99 % at 0.3 µm for ISO 7–8; 99.9995 % for ISO 5.
- Speed controller – Lets you dial airflow to meet target air-change rate.
- Optional LED or pressure monitor – Confirms filter health at a glance.
Because everything is integrated, installation is as simple as hanging the unit or setting it atop a tubular frame.
2 | Why choose an FFU over a hard-wall cleanroom?
| Factor | Hard-wall build-out | FFU clean zone |
| Capital cost | $150–300 / sq ft | $35–60 / sq ft |
| Lead time | 8–16 weeks | 1–2 weeks |
| Permits & HVAC | Often required | Usually not |
| Flexibility | Fixed walls | Modular—expand or relocate |
| ISO capability | ISO 8 → ISO 5 | ISO 8 → ISO 5 (with multiple FFUs) |
For small inspection cells, FFUs hit the sweet spot: clean enough, fast enough, and cheap enough to justify in-house measurement—or a dust-free assembly bench for miniature sub-assemblies.
3 | Selecting the right ISO class
Most machine-shop inspection needs fall between ISO 7 and ISO 8. The ISO classification dictates air-change rate (ACR) and therefore FFU count.
| ISO Class | Typical application | ACR (changes/hr) |
| ISO 8 | Visual inspection, surface-finish checks | 10–20 |
| ISO 7 | CMM, optical measurement, electronic sub-assembly | 30–60 |
| ISO 6 | Laser metrology, microfluidic assembly | 90–180 |
| ISO 5 | Semiconductor or implantable devices | 240–300 |
Rule of thumb: one 2 × 4 ft Air-Fit FFU moving 650–700 CFM will support ~80–90 sq ft at ISO 8, ~40 sq ft at ISO 7, and ~15 sq ft at ISO 6.
4 | Building your modular clean zone—step by step
- Pick the footprint
- Map machine layout and material flow; allow 3 ft clearance for carts and operators.
- Common sizes: 8 × 8 ft (ISO 7 CMM corner) or 12 × 16 ft (ISO 8 manual assembly).
- Choose a frame system
- Aluminum T-slot or powder-coated steel tubing. A simple “goal-post” frame with vinyl curtains is enough for ISO 7–8.
- Add clear polycarbonate panels for ISO 6+.
- Specify FFU quantity
- Use the table above or the calculator on our Air-Fit page.
- Arrange units evenly to avoid dead zones; overlap airflow cones by ≈10 %.
- Install electrical
- Each Air-Fit FFU draws < 1 A @ 120 V; multiple units can daisy-chain to a dedicated circuit.
- Optional VFD controller lets you fine-tune velocity and noise.
- Seal the perimeter
- Overlap curtains 3–4 in, weight the hem, and tape floor seams for ISO 7 or better.
- For ISO 5–6, add a pass-through air shower or mini-antechamber.
- Verify performance
- Use a handheld particle counter; ISO 7 requires < 352 000 particles ≥ 0.5 µm per m³.
- Record results for your customer quality audits.
5 | Typical cost breakdown (8 × 8 ft ISO 7 cell)
| Item | Qty | Cost each | Extended |
| Air-Fit FFU (2 × 4, HEPA) | 2 | $1 650 | $3 300 |
| T-slot frame kit | 1 | $1 200 | $1 200 |
| Vinyl strip curtains + fasteners | 1 | $450 | $450 |
| Electrical supplies | — | $150 | $150 |
| Labor (8 hrs @ $60) | — | $480 | $480 |
| Total | ≈ $5 600 |
Compare that to $50 000+ for a turnkey hard-wall ISO 7 room of the same size.
6 | Maintenance tips to keep ISO numbers intact
- Check pre-filters monthly; vacuum or replace when dust-gray.
- Monitor pressure drop—Air-Fit’s optional Magnehelic gauge turns yellow at 1.0 in wg, signaling HEPA replacement.
- Record particle counts every six months or after major layout changes.
- Wipe curtains and surfaces with IPA weekly; airborne particles settle fast in laminar zones.
- Log everything—maintenance records are your evidence during supplier audits.
7 | Case snapshot: Contract shop saves three days per job
A Michigan medical-device machine shop shipped parts 30 miles to an external lab for first-article inspections—adding three days to every production run. An 8 × 12 ft ISO 7 cell built with three Air-Fit FFUs cost $8 k total. Payback came in six months through:
- Elimination of courier fees
- In-house adjustments on day one instead of day four
- Higher yield thanks to instant feedback on surface finish
Conclusion & next steps
You don’t need a six-figure budget or cleanroom contractor to hit ISO-class air quality. A handful of fan-filter units, some modular framing, and a free weekend can turn any corner of your machine shop into a high-precision inspection or assembly zone.
Ready to design yours?
- Download our FFU sizing worksheet to calculate airflow and ISO class.
- Talk with an Aeroex specialist about the Air-Fit lineup—HEPA or ULPA options, EC fan drives, and integrated lighting to brighten the workspace.
- Need a turnkey kit? We can pre-cut frame members and ship a bolt-together bundle to your dock.
Clean parts, faster feedback, happier customers—that’s the power of an affordable clean zone built on Air-Fit FFUs.
Since 2002 Aeroex Technologies has delivered engineered air-filtration solutions that help North American manufacturers breathe easier, inspect faster, and ship with confidence.
