What Is a Clean Booth? The "Lightweight" Cleanroom
A clean booth (also called a clean tent or clean canopy) is a localized cleanliness device. It uses an aluminum or stainless-steel frame with a row of FFU fan filter units on top and anti-static curtains (or hard wall panels) around the sides, creating a small ISO 5–7 clean zone inside an ordinary plant.
An analogy: building a full cleanroom is like fitting an entire house with an air-purification system; a clean booth is like pitching an "air tent" inside a large room — you clean only the small area that actually needs it and leave the rest as is.
For many factories, not every corner needs cleanroom-grade air; often only a particular inspection station, assembly bench, or process point does. Rather than spending big on a full cleanroom, a Clean Booth delivers a local upgrade — which is why it sees steady demand among cleanroom equipment.
How Does a Clean Booth Work? Ceiling FFUs + Laminar Flow + Curtain Enclosure
A clean booth's cleaning power comes mainly from the row of FFU fan filter units on top. The FFUs draw in air from above, pass it through HEPA filters, and push it down into the booth as even vertical laminar flow. Clean air flows top-down through the work area, pushing particles down and out, finally spilling through the gaps at the curtain hem into the plant — because the booth holds positive pressure, dirty air cannot flow back in.
Three key points in this design:
- ▸FFUs are the heart: cleanliness depends almost entirely on FFU coverage (outlet area as a share of the ceiling) and filter grade.
- ▸Positive-pressure spillover: booth pressure is slightly above ambient, spilling out continuously at the curtain hem to block outside contamination.
- ▸Downward laminar flow: vertical, even airflow is the key to carrying particles away from the work area; turbulence makes particles swirl inside.
An honest caveat: a clean booth is less stable than a full cleanroom. Its return air mostly spills into the plant, temperature/humidity usually rely on existing facility HVAC, and sealing is weaker than solid walls. It solves "local, good-enough" cleanliness — not "full-path, ultimate" control.
When Should a Clean Booth Replace a Full Cleanroom?
This is the most common question. The answer depends on whether your cleanliness need is "local" or "full-path."
A simple rule of thumb:
- ▸Choose a clean booth: only specific benches/process points need cleanliness, budget is limited, you need fast deployment (days to weeks), you may move or expand later, or you don't want to remodel the existing plant.
- ▸Choose a full cleanroom: an entire line needs full-path cleanliness, you need precise temperature/humidity control, you must reach ISO 4 or better, or the process demands extreme environmental stability.
In practice the two are often combined: control the base environment with a cleanroom (say ISO 7), then add clean booths at critical points to upgrade locally to ISO 5.
Soft Curtain vs Hard Wall: Choosing the Enclosure
There are two mainstream ways to enclose a clean booth, differing mainly in sealing, cost, and durability.
| Dimension | Anti-static PVC curtain | Hard wall (steel / acrylic) |
|---|---|---|
| Cost | Low | Higher |
| Sealing | Moderate (gaps between strips) | Good (near solid wall) |
| Cleanliness ceiling | Stable at ISO 6–7 | Can push ISO 5 |
| Flexibility | Adjustable, movable anytime | More fixed |
| Visibility | Transparent, easy to monitor | Depends on panel |
| Durability / cleaning | Ages, needs periodic replacement | Durable, easy to clean |
Selection logic: high cleanliness requirement and long-term fixed use → hard wall; budget-first, flexibility needed, ISO 6–7 sufficient → anti-static curtain. You can also mix — three hard walls with one curtain side as the entrance.
Cleanliness Class and FFU Configuration
The class a clean booth can reach depends mainly on FFU coverage. The table below shows common configurations.
FFU coverage follows the same logic as multi-stage cleanroom filtration: coverage = total FFU outlet area ÷ ceiling area. ISO 5 often needs 60%+ or full coverage; ISO 7 needs only 25–40%. The HEPA grade paired with the FFU must match too — see the FFU selection guide and HEPA/ULPA filters.
Selection and Procurement Notes
Before buying a clean booth, clarify these points:
- 1Target class: which ISO class? This sets FFU coverage and enclosure type.
- 2Size and height: how large is the work area? Is plant headroom enough for FFUs + frame?
- 3FFU count and motor: compute coverage for the FFU count; for many units running long hours, choose DC/EC energy-saving motors.
- 4Enclosure material: curtain or hard wall, by cleanliness and flexibility needs.
- 5Floor and return: do you need a floor return (required for higher class)?
- 6Entrance design: for frequent entry and high cleanliness, pair the entrance with an air shower as a buffer.
- 7Temperature/humidity: if booth needs exceed plant HVAC capacity, plan separately.
A clean booth looks simple, but "whether it meets spec" depends on the interplay of FFU coverage, enclosure sealing, and return-air design. Ask the supplier how they verify the rated class (particle counting per ISO 14644-1) rather than relying on catalog claims.
FAQ
Q: Can a clean booth really reach ISO 5 (Class 100)?
Yes, conditionally. Reaching ISO 5 usually requires FFU coverage of 60%+ (often near full), ideally with hard walls or well-sealed curtains plus a floor return. Insufficient coverage or a leaky enclosure and measurements won't get there. In short, an ISO 5 clean booth isn't cheap — but it's still far below building a full ISO 5 cleanroom.
Q: What exactly is the difference between a clean booth and a cleanroom?
The biggest difference is "scope" and "completeness." A cleanroom builds the whole room as a set (walls, ceiling, floor, HVAC, pressure cascade); a clean booth only encloses a local zone with FFUs + curtains, borrowing return air and temperature/humidity from the plant. A cleanroom has a higher, more stable cleanliness ceiling but costs several times more and takes longer.
Q: Do anti-static curtains generate static that attracts particles?
Ordinary PVC curtains can indeed build static through friction, attracting particles or even discharging onto sensitive components. So electronics and semiconductor settings should use anti-static PVC curtains, whose treated surface dissipates static. Specify the anti-static grade when ordering — don't substitute ordinary clear PVC.
Q: How many FFUs does one clean booth need?
It depends on ceiling area and target coverage. For a 2.4m×1.2m workstation targeting ISO 6 (~50% coverage): ceiling area is 2.88 m², required FFU outlet area ~1.44 m²; with standard 1200×600 FFUs (0.72 m² outlet) that's about 2 units. ISO 5 might need 4+ for near-full coverage.
Q: Can I DIY-assemble a clean booth?
Assembling the frame and curtains is relatively simple, but "meeting the class" isn't just bolting parts together. Miscalculated FFU coverage, a leaky enclosure, or an unplanned return path will miss the target. At minimum, consult a professional for the cleanliness planning and FFU sizing; you can self-assemble, but always do particle measurement at acceptance.
Q: How is a clean booth's cleanliness verified?
Per ISO 14644-1, use a particle counter at multiple sampling points inside the booth to measure ≥0.5μm (and ≥0.1μm if needed) concentrations against the target class limit. Measure in the "operational" state (with staff working) to reflect real use. FFUs should also undergo periodic HEPA integrity (PAO) testing.