17 Feb Cleanroom Wall Finishes: Cleaning, Sealing & Contamination

Unfortunately, contamination in cleanrooms isn’t always easy to see. While HEPA filtration and airflow controls help, wall seams, rough surfaces, and low-quality sealing can attract and trap particles, which makes cleaning in general less effective. The right wall finishes, joint sealing, and cleaning protocols can have a huge impact on your contamination control strategy. In this article, we’ll cover how different cleanroom wall finishes impact contamination control, why some materials are easier to clean than others, the best disinfectants for various surfaces, how proper sealing prevents contamination, and more.

Why Wall Finishes Matter for Contamination Control

When designing a cleanroom, choosing the right wall finishes can significantly improve contamination control. On the other hand, if wall materials are not chosen carefully, they can become harder to clean, break down because of disinfectants, or trap particles and microbes. This is why contamination control strategies (CCS) must account for wall finish compatibility from the beginning.

Cleanroom walls are exposed constantly to airborne particles, disinfectants, and personnel, which can counteract important primary engineering controls like HEPA filtration and controlled airflow.

To achieve the most contaminant-free environment possible, cleanroom walls must be made of materials that withstand frequent cleaning, can be sealed effectively, and comply with relevant regulations.

Why Do Cleanroom Walls Require Specialized Cleaning?

As we alluded to earlier, there is a sense of false hope that primary engineering controls such as HEPA equipped fan filter units, temperature, differential pressure, humidity will be enough to maintain the right level of cleanliness. Unfortunately, rapid air movements coming from personnel, equipment, and other activities can work against them, which is why it’s important to reduce these effects as much as possible.

Choosing the right wall finishes, as well as cleaning them with the right agents, can help you control your environment better. Different cleaning agents will impact how well they can be disinfected and maintained.

Without such specialized cleaning, walls can accumulate various particles, bacteria, or residues that may not only affect your product, but the walls themselves. Also, keeping clean walls is paramount to staying in compliance with ISO, GMP, and other regulations.

Best Cleaning Methods and Disinfectants

Since cleanrooms are built with different materials and architectural finishes, not all cleanroom walls can be cleaned in the same way. Different materials may react poorly to some disinfectants, while tolerating others; and some may require special cleaning methods to avoid damage.

Some common disinfectants used in cleanrooms include:

• Isopropyl Alcohol: Great for neutralizing bacteria and viruses, but does not kill spores.
• Hydrogen Peroxide: Excellent for sterilization and killing spores; it can break down into water and oxygen without harmful residues.
• Quaternary Ammonium Compounds (Quats): Broad-spectrum disinfectants that kill bacteria, viruses, mold, and fungi. They are odorless, non-corrosive, and EPA-registered, making them a safer alternative to bleach with shorter dwell times.
• Chlorine-Based Disinfectants: Highly effective, but can be hazardous if mixed with certain chemicals (producing chlorine gas) and may corrode some surfaces over time.

Common Practices for Cleaning Cleanroom Walls

To keep cleanroom walls contamination-free, it’s important to use lint-free wipes (so that they won’t shed fibers into the air). Generally speaking, always clean from top to bottom so that particles won’t spread to already-cleaned areas. Cycling/rotating disinfectants may also prevent microbes from developing resistance, and as always, make sure you are following the cleaning protocols in relevant regulations and guidelines (whether ISO, GMP, USP 797/800, etc.).

Cleaning Challenges by Wall Type

Different wall materials require different cleaning approaches to avoid damage while ensuring contamination control:

• Insulated Metal Panels (IMPs): Can handle strong disinfectants, but may need streak-free wiping to prevent residue from building up.
• Composite Panels (FRP, PVC): Highly resistant to chemicals, but may degrade over time with repeated exposure.
• Liner Panels: May require extra sealing at the edges to prevent contamination buildup.
• Epoxy-Coated Drywall: Prone to chipping, so may require gentle cleaners.

Sealing for Performance: Why It Matters for Contamination Control

While choosing the right wall finishes is important for cleanability, sealing is perhaps just as important to ward off contaminants. Even well-cleaned walls can become a risk if their seams and joints aren’t properly sealed.

How Sealing Prevents Contamination

Seams and joints in cleanroom walls can let in microbes, other particles, and air, which makes it harder to create a truly controlled environment. When proper sealing is used, it will prevent the buildup of microbes and other particles, improve the cleanability of walls by removing crevices that are hard to reach, and reduce the chances of air leaks.

If a cleanroom isn’t properly sealed, it may fail environmental monitoring (EM) checks, which leads to compliance issues and, of course, increased contamination risks.

Common Sealing Methods

Different wall types will require different sealants, but here are a few of the most common methods:

• Silicone Caulking: A flexible and low-cost choice, but may require reapplication if there is repeated exposure to chemicals, or if there is a lot of movement in the wall panels.
• Chemical Cold Welding: A chemical bonding method that fuses wall panels. Does not require as much maintenance as caulking.
• Heat-Welded Seams: Commonly used for vinyl-covered walls.
• Integrated Coving: Creates smooth transitional areas between walls and floors, removing sharp corners.

Whatever sealing you use for cleanroom walls, make sure it is intact and inspected regularly. Always make sure to use compatible cleaning agents, as the wrong disinfectant can damage the sealings.

NIH Study Findings on Cleanroom Hygiene

Recent NIH research has revealed more information about how contamination spreads in cleanrooms, especially regarding how cleaning and sealing practices impact microbial control. Here are a few relevant research findings.

Research Findings

• It is now known that surface roughness affects microbial contamination. Rougher surfaces retain more bacteria, which underscores the importance of smooth, non-porous wall finishes (See NIH research).
• Different disinfectants can vary in their effectiveness (See NIH research).
• Similarly, the disinfectant effectiveness is influenced by the architectural finish it is used on (See NIH research).

Implications for Cleanrooms

• Some cleaning protocols will need to be adjusted based on the wall finishes used. Some materials may require gentler disinfectants to prevent the breakdown of finishes and wall materials, while others may need stronger agents to eliminate microorganisms.
• Wall material selection should prioritize smooth and non-porous surfaces. Because rough surfaces retain more bacteria, cleanroom designs should use finishes that minimize microbial buildup and that can be more easily disinfected.
• Sealing methods must be regularly inspected and maintained. Gaps, seams, and worn-out sealants can create spaces for contaminants to linger in, so routine checks and resealing are important to stay in compliance.
• Disinfectant selection should be compatible with architectural finishes. Using the wrong disinfectant on a specific wall finish can reduce its effectiveness, damage the material, or leave behind residues that can increase contamination.

The Bottom Line

In short, the right cleanroom wall finishes can make a big difference in how easy surfaces are to clean, how well they resist contamination, and how long they last. Choosing smooth, non-porous materials, sealing them properly, and using the right cleaning methods will help keep your cleanroom compliant and contamination-free.

Interested in building a new cleanroom? Reach out to the experts at Allied Cleanrooms for a quote on new spaces: