Air cleanliness and particle deposition rate: Data assessing the effectiveness of a polymeric mat

Air cleanliness and particle deposition rate: Do polymeric mats really make a difference?

In cleanroom environments, limiting dirt and particles brought in from outside is a key factor for ensuring research and production quality. One widely used solution is a tacky polymeric mat (polymeric mat) placed at entry/exit points, intended to retain particles and microorganisms from personnel footwear.

However, an important question remains: do polymeric mats directly affect air cleanliness and particle deposition rate inside the cleanroom?

Polymeric mats and their impact on particles

Various studies have shown that polymeric mats can retain particles and microorganisms effectively when people walk across them.

The tacky surface helps reduce particle ingress into the cleanroom, thereby supporting maintenance of required cleanliness.

Even so, evidence specifically demonstrating a direct impact on air cleanliness and on particle deposition onto surfaces remains limited, and more data is still needed for firm conclusions.

An experimental study in a cleanroom

At a facility manufacturing semiconductor-processing equipment, specialists from Brookhuis Applied Technologies, NTS, and Dycem carried out a real-world investigation. They compared particle contamination levels with and without a polymeric mat installed at the cleanroom entrance.

Initial findings suggested the polymeric mat had a positive effect in reducing particles transferred from footwear, but detailed data on changes in air cleanliness and particle deposition rate still requires further study.

Temporary sticky mats vs fixed polymeric mats

Temporary sticky mats: Consist of multiple layers of adhesive plastic film that can be peeled away when dirty. The advantage is easy replacement, but a drawback is that peeling can re-disperse particles back into the air during layer removal.

Fixed polymeric mats: Made from materials such as polyester or PVC and often described as working via electrostatic attraction/tack. They can be more effective, but they require regular and thorough cleaning to maintain performance.

Conclusion and recommendations

Polymeric mats play an important role in reducing the number of particles and microorganisms brought in from footwear, helping to maintain cleanroom protection. However, to confirm a clear relationship between mat usage and air cleanliness as well as particle deposition rate, more in-depth studies are still needed.

• Prioritise fixed polymeric mats over temporary peel-off mats where long-term performance is required.

• Combine mats with other controls such as airflow management, routine cleaning, and cleanroom garment discipline.

• Invest in additional measurement and monitoring to quantify air-quality improvement when polymeric mats are used.

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