Understanding Particle Adhesion in Cleanrooms: Causes, Risks, and Effective Removal

Particle contamination in cleanrooms is a persistent challenge in industries like pharmaceuticals, biotechnology, and semiconductor manufacturing. Whether viable (living microorganisms) or non-viable (dust, residues, or endotoxins), particles can strongly adhere to surfaces, making them difficult to remove. This adhesion increases the risk of contamination, impacting both cleanroom operations and product quality.  

Controlling contamination requires an understanding of why particles adhere to surfaces and how to break those bonds to remove them efficiently. This blog will explore the key forces behind particle adhesion, the risks of contamination, and why using wetted cleanroom wipes and mops is the most effective method for removing these particles—including endotoxins—from cleanroom environments.  

What Causes Particles to Adhere to Surfaces?   

Particles settle onto cleanroom surfaces due to four primary forces:  

• Gravity – The natural pull of gravity causes particles to settle on horizontal surfaces, like floors and workstations. The larger (more massive) the particle, the greater the force.  

• Van der Waals Forces – Molecular forces cause particles to "stick" to surfaces through atomic-level attractions. These are the strongest forces on particles unless humidity is present.    

• Electrostatic Charges – Opposite charges between a particle and a surface can cause them to cling together, similar to static electricity. These forces vary widely depending on environment and surface conditions.  

• Capillary (Hydroscopic) Forces – Moisture on surfaces creates a "bridge" between particles and the surface, increasing adhesion. In the presence of humidity common to many controlled environments, these can be the strongest forces acting upon particles.  

Why Particle Adhesion Matters  

Once particles adhere to a surface, cleanroom airflow alone is not enough to dislodge them. These contaminants remain unless physically or chemically removed. Wetted cleanroom wipes and mops are essential for breaking adhesion forces and ensuring effective particle removal.  

Viable vs. Non-Viable Contaminants  

Viable Particles  

• These are living microorganisms such as bacteria, yeasts, and molds that can multiply if not properly controlled.  

• Viable particles are a major concern for pharmaceutical and biotech cleanrooms due to their potential to contaminate sterile products.  

Non-Viable Particles  

• These are particles that are not living. However, the remnants of dead microorganisms (like endotoxins) and non-vegetative spores are also classified as non-viable particles.  

While viable particles are often the focus of microbial control efforts, non-viable particles are equally dangerous as they are the carriers of viable microorganisms. As shown in many tests and several studies, the cleaning techniques used to remove non-viable particles are also effective for viable particle control. The very act of controlling generic “particulate contamination” inherently results in controlling microorganisms and endotoxins as well.   

Both viable and non-viable particles can be effectively removed using wetted wipes and mops. This method disrupts adhesion forces and prevents recontamination.  

How to Remove Particles from Cleanroom Surfaces 

Since particles are bound to surfaces through strong physical forces, cleaning methods must actively break those bonds to remove contaminants. 

1. Mechanical Cleaning (Wiping and Mopping)  

How it works:  

• Wiping and mopping physically dislodges particles by disrupting adhesion forces, breaking the particles free of the surface. 
•  Once liberated from the surface being cleaned, the particles are subject to removal from the surface.     
  

2. Wetted Wipes and Mops: The Most Effective Particle Removal Tools 

How it works:  

• Once free of a surface due to the mechanical action of wiping or mopping, particles in contact with the wipe or mop surface become entrapped by the fiber structure of the wipe or mop.   
• The moisture on the wipe or mop introduces overwhelming hydroscopic forces, causing particles to be drawn into and captured by the fibers of the wipe or mop, increasing particle removal effectiveness and preventing redistribution.  
• Presaturated wipes provide consistent moisture levels, ensuring uniform particle removal and reducing variability in cleaning performance.  

Best Practices for Particle Removal in Cleanrooms   

• Train personnel in understanding particle adhesion and the correct wiping and mopping techniques to remove particles and prevent redeposition of contaminants.    

• Prevent the introduction of contaminants by ensuring proper gowning, operator behavior, material control, and cleaning best practices.   

• Use cleaning tools designed for controlled environments to maximize cleaning and minimize cross-contamination.   
• Validate cleaning protocols to ensure particle removal is effective and consistent. 

Conclusion

Particle adhesion is a significant challenge in cleanroom environments, but it can be effectively managed with the right cleaning methods and tools. Since particles and endotoxins adhere to surfaces in a variety of ways, understanding particle adhesion in cleanrooms is key to designing protocols for effective removal and control. Using wetted wipes and mops is the easiest and most effective to break adhesion forces and ensure particles are completely removed from the cleanroom.  

Contec’s offering of dry and presaturated wipes, engineered fabric and microfiber mops, and advanced cleanroom cleaning solutions are designed to optimize particle removal, minimize contamination risks, and help maintain regulatory compliance.