How to Mitigate Contamination on Pharmaceutical Cleanroom Flooring 

In the pharmaceutical industry, contamination control efforts often focus on eye-level, hand-level, and operational areas. While these visible spaces receive significant attention, a major oversight persists in floor-level contamination. Many mistakenly believe that routine cleaning and maintenance are sufficient to eliminate microbiological and particulate contaminants from floors.

However, floor-level contamination is a hidden threat that demands our attention and must be considered in your Contamination Control Strategy (CCS). This blog post will explore the causes and types of floor-level contamination in pharmaceutical cleanrooms and provide simple yet effective solutions to address this often-overlooked issue.

Where does the contamination come from?

Floor-level contamination can originate from various sources in critical environments. While not all contaminants are generated at floor level, many can settle there from above. Once on the floor, these contaminants pose an increased risk when they are reintroduced to operational areas.

For example, fibers that land on the floor may be crushed and reduced in size by foot traffic or wheeled equipment. These smaller particles can become airborne more easily, potentially contaminating products or surfaces at the operational level. This cycle of contamination highlights the need to prioritize floor-level cleanliness in pharmaceutical cleanrooms.

Figure 1: Potential Sources of Contamination 

Studies have shown that a staggering 80% of contamination enters critical environments on the floor system via feet or wheels. This statistic underscores the importance of focusing contamination control efforts at the floor level. In the event of a contamination incident, investigating foot-borne and wheel-borne patterns should be a top priority.

Types of Contamination in Pharmaceutical Cleanrooms

Microbiological Contamination

Viable microbiological contaminations include the presence and growth of bacteria, yeast, mold and viruses. They can appear from multiple sources, and identifying the specific type of microbial contaminant can reveal its source. Identifying these organisms, at least to the genus level, will help direct the sanitation teams toward appropriate treatment methods. Without proper identification, teams may use ineffective or unnecessarily costly treatments.

Biofilms

Biofilms pose a particular challenge. If allowed to establish due to improper or infrequent cleaning, they can be extremely difficult to eliminate and may develop chemical resistance or release organisms post-disinfection.

Mold Contamination

Mold warrants particular attention, as it is difficult to remove once settled. Floor-level mold can occur where moisture and nutrients are present, especially in hidden areas of your cleanroom design. Visual elimination is insufficient, and proper identification is essential for effective treatment.

Mold spores are especially concerning due to their small size and ability to become airborne. They can lodge in hard-to-reach areas and spread throughout a facility via foot and wheel traffic.

Particulate Contamination

Particulate contaminants can originate from various sources, including disinfecting cloths, gowns, human activity, metals, rubbers, and plastics. These particles can range from visible (>100µm) to sub-visible sizes and can be further broken down and spread through foot and wheel traffic.

Figure 2: Particulate Sizes

Both particulate and microbiological contaminants carried on trolley wheels are a noteworthy source of risk in a laboratory. The rough texture seen on trolley wheels can easily hold these contaminants, and wheel movement can be significantly greater than human foot traffic. While a person may stand in a particular spot with little movement while operating, they often move a trolley quite frequently in a space around them. Trolley wheels can subsequently have numerous rotations in a small area and, if contaminated, can release particles, which will be deposited into the air stream.

How to Control the Risks of Contamination on Pharmaceutical Cleanroom Flooring

Maintaining the highest levels of cleanliness in cleanroom environments requires preventing particles and microorganisms from entering critical areas. Good Manufacturing Practice (GMP) and quality assurance principles demand minimizing particle and microbiological contamination to protect product integrity.

Before addressing ground-level microbiological contamination, it’s important to understand the potential floor flora. This assessment raises several vital questions:

1. Are pharmaceutical environmental monitoring programs including floor and trolley wheel surfaces in their testing protocols?
2. Should swab or contact plate methods be employed for surface testing?
3. What is the rationale for including or excluding these surfaces in monitoring programs?
4. Is there a risk of mold, mold spores, soil, or other contaminants on trolley wheels?
5. If trolley wheels are disinfected, how are potential contaminations between cleanings addressed, especially if cleaning is ineffective or incomplete?
6. Would it be beneficial to periodically include wheel surfaces in environmental monitoring programs, particularly for trolleys moving between rooms?

The remainder of this chapter will analyze some of the most used forms of floor-level contamination control currently employed in pharmaceutical manufacturing facilities. These methods aim to address the challenges identified and maintain the highest standards of cleanliness in these areas.

Floor Solutions for Pharmaceutical Cleanrooms

Peel off Mats

Peel-off “sticky mats” are the most common form of floor-level contamination control in pharmaceutical manufacturing environments. The healthcare industry, including pharmaceutical manufacturing, spends an estimated $350 million annually on these mats, making them the second-largest consumable expense after gloves.

These mats consist of 30-60 layers of single-use plastic sheeting coated with adhesive, designed to capture particulates from feet and wheels. Once the adhesive becomes saturated, the top layer is peeled away to expose a fresh layer. Typically, they are placed outside critical areas, at cleanroom entrances, in personal airlocks, or in materials airlocks. Sizes range from 18″ x 36″ to 36″ x 60″, although 24″ x 36″ is most common.

Despite their popularity, several factors should be considered when using sticky mats. Studies indicate they are only 27% effective in preventing foot and wheel-borne contamination. Their smaller surface area compared to alternative solutions may compromise decontamination efforts, and peeling off layers can release up to 215,000 particles back into the air. Additionally, each peel generates a ball of contaminated waste, leading to significant disposal costs and environmental concerns. Even with multiple mats, up to 20% of contamination can still enter clean rooms. Therefore, pharmaceutical companies must assess the effectiveness and long-term costs of peel-off mats and consider alternative solutions for optimal contamination control.

Size

Put simply, peel-off mats are too small to decontaminate feet and wheels effectively. It has been established that at least 6 footfalls (3 on each foot) must meet the contamination control surface to effectively control foot-borne contamination. For wheel-borne contamination, a minimum of three wheel rotations need to be achieved on the contamination control surface.

A single peel-off mat will only allow for 1 or 2 footfalls (as displayed in Figure 3) on the adhesive surface and, in some cases, can be avoided altogether. With such a small surface area, it is necessary for the operators to step on the mat several times with each foot to achieve 6 footfalls. This practice is inconvenient and could be overlooked during day-to-day operations.

For wheeled traffic, achieving three-wheel rotations without ‘ganging’ several peel-off mats together to make a larger surface area is impossible. This ‘ganging’ practice is problematic as it creates ‘gaps’ where contaminants can gather.

Particle Transfer

Numerous studies have shown that peel-off mats are ineffective at containing particulate matter in sterile conditions and, in some cases, can increase particulate matter on the foot or wheel. This is likely due to the mat’s adhesive quality quickly diminishing after one footstep. Therefore, when another operator steps in the same place (overstrikes) on the peel-off mat, more particles are deposited onto the shoe than are removed.

Sandle also found that peeling an adhesive mat generates a relatively high number of airborne particles, which is highest when the mat is heavily soiled. The level of airborne particles increases when the mat’s top surface is peeled quickly. So again, the cleanroom operator must peel the top layer in a controlled manner to minimize airborne particle transfer. This can exasperate any floor-level contamination into the cleanroom.

Wheeled Traffic

Most peel-off mats are too small to allow three full-wheel rotations of any cart or pallet jack being driven over them. Another issue with heavy traffic from wheels is the plastic sheets wrapping around the wheels of the cart/pallet jack and jamming them. This is not only inconvenient but also poses a health and safety risk.

Peel-off mats are not designed to handle heavy wheeled traffic, like motorized palate jacks or forklift trucks. A pallet jack could easily tear through multiple layers of plastic, rendering them useless and in need of replacement, leading to increased cost.

Health and Safety

There are several health and safety risks associated with the use of peel-off mats, which should be considered when using them in a pharmaceutical manufacturing environment.

Peel-off mats can present a trip hazard, and there have been numerous recorded incidents where operators have tripped on them. This is either because they are too sticky and cause the operator to overbalance, or they have become de-laminated from the subfloor, and the corners of the mats have peeled up, or shoes or shoe covers may stick and cause falling or tripping to occur.

Another consideration is the strain on the cleanroom operators’ backs. Bending over to peel a layer of plastic can be tricky, requiring a significant amount of physical effort and the potential to cause injury if not done correctly.

Finally, as already discussed, peel-off mats release particles back into the atmosphere when peeled. The act of peeling requires a cleanroom operator to be in close proximity to the mat, which means there is potential for harmful contaminants to be inhaled.

Convenience

Peel-off mats are often considered the easiest, most convenient form of floor-level contamination control. They can be ordered as needed and self-installed at short notice. No cleaning is required to rejuvenate the adhesive surface, and the operator simply needs to peel the soiled top layer of plastic and dispose of it.

Peel-off mats need to be replaced on a regular basis. Most mats are 30 layers of plastic, so if peeled once per day, this will be a monthly task. Replacing a peel-off mat can be time-consuming as the floor needs to be cleaned of any residual adhesive that may have leached onto it, and the new mat needs to be carefully placed to ensure no air bubbles are present. The subfloor also needs to be thoroughly sterilized to ensure no microbial contaminant is present beneath the peel-off mat. This can mean that the area must be closed for some time when installing a new peel-off mat.

Peel-off mat inventory must be stored in a specific way to ensure that mats do not become damaged or warped before use. Depending on the number of peel-off mats used in the facility, this can take up considerable shelving space.

Environmental

The layers of plastic and adhesive that make up a peel-off mat are non-recyclable. The multiple layers of plastic are disposed of in general trash (after decontamination) or contaminated waste drums for incineration. Research suggests that peel-off mats are less environmentally friendly than other methods of floor-level contamination control.

One study estimated that the greenhouse gas emissions associated with a pharmaceutical manufacturing facility, using peel-off mats in 10 locations could produce as much as 70,000 kg of CO2 for the manufacture of the product and a further 55,000 kg for the disposal of the used peel-off mats, if incinerated.

As most of these contain acrylic adhesives and polyethene film, the cost of removal of the acrylic adhesives is substantial and should be conducted before disposal in a landfill of the remainder of the used “peel-off” materials. Contamination peel-off mats from hospitals are required to be “de-contaminated” before being sent to landfill.

The waste generated from mats that are not incinerated or decontaminated is non-recyclable and, therefore, must go to landfill, adding to the growing global problem of plastic waste.

Costs

Peel-off mats are often considered an immediate cheaper option for floor-level contamination control. However, the costs vary significantly depending on size and the manufacturer/supplier. When analyzed over three to five years, the cost of using peel-off mats is considerable.

On average, the cost per peel of a peel-off mat is around $0.50 before the cost of disposal is added. If the peel-off mats need to be decontaminated before disposal, the price per peel can double. A 24/7 facility peeling mats five times per shift, three shifts per day, will spend around $9,000 per annum per peel-off mat location.

These costs can increase through poor operator behavior, such as peeling more than one mat at a time or carrying heavy loads across the peel-off mat, which can damage it.

Polymeric Flooring

Polymeric flooring is a specialized contamination control solution made from a non-toxic, plasticized material pressed onto a non-permeable substrate. It features an optically smooth, soft, and supple surface with natural tackiness and high levels of short-range electromagnetic forces (Van der Waals). These properties attract and retain both viable and non-viable particulate contamination that comes into contact with its surface. The primary function is to capture particles and hold them until they can be removed through cleaning and disinfection, making it a hygienic tool for maintaining cleanliness in controlled environments.

Most polymeric floors require professional cleanroom design and installation and are affixed to the existing subfloor using adhesive tapes. They typically incorporate a tapered edge sealed to the subfloor to prevent water ingress and inhibit the growth of mold or other microbial contaminants beneath. At Dycem, our seamless pharmaceutical flooring has a 3-5 years lifespan, during which the surface remains tacky enough to effectively trap and retain particulates. This durability makes it a valuable solution for long-term contamination control.

Size

Polymeric flooring is supplied in rolls, and most manufacturers produce rolls that are 6’6” in width and 40’ in length. The minimum recommended length of material is 10’, which allows 6 footfalls or 3 complete wheel rotations. However, the flooring can be customized to fit any room size or layout.

Polymeric flooring should be installed in a way that cannot be avoided, either wall-to-wall or across the entire width of the door so that it can capture more footfalls in the natural course of walking. This will reduce ground-level contaminants entering the critical space (Figure 4).

You should always consider the amount of traffic crossing the mat, as high-traffic areas will require a great surface area to ensure the material does not become saturated in contamination between cleanings.

Particulate Reduction

Research suggests that polymeric flooring is a superior contamination control method for peel-off mats.

In a 2002 study, Clibbon swabbed cleanroom operators’ footwear before and after walking across a peel-off mat and a polymeric floor (after making four footfalls on each surface). She also took swabs from trolley wheels before and after being pushed across both types of flooring.

The results showed a reduction of 25.2% and just 11% in wheel and foot-borne contamination, respectively, after contacting a peel-off mat, compared to 99.8% and 99.9% after contacting a polymeric floor.

Sandle analyzed the surface particle count of shoes and overshoes before and after walking on 6 different brands of peel-off mats and 2 polymeric flooring mats (one new and one 2-year-old).

The results showed a reduction in particles from shoes of between 20% and 52% after stepping on a peel-off mat, compared to a 77% reduction after stepping on ‘old’ polymeric flooring and an 82.1% reduction after stepping on new polymeric flooring.

When compared against peel-off mats, polymeric flooring is much more effective at reducing particulates of 10 microns and below. In his 2009 paper, Prout examined studies by the University of Bath and Strasbourg. Both studies examined particle reduction from feet and wheels of particles of different sizes. Above 25 microns, the performance of polymeric flooring and peel-off mats is largely similar; however, for particulates of 10 microns or smaller, the results are radically different

Figure 5 – Particulate Reduction Data

Wheeled Traffic

Polymeric flooring is the superior system for removing particulate matter from wheeled traffic. This is due to the size of the contamination control area and the wheels’ ability to achieve multiple rotations on the flooring.

Other practical considerations that further support the use of polymeric flooring in areas where wheeled traffic will be present include:

• Polymeric flooring is ‘tacky’ not ‘sticky,’ and most manufacturers install it with a diminishing edge strip that allows a smooth transition onto the flooring. Therefore, carts and trolleys can pass easily across the surface without interrupting the cargo.
• Manufacturers of Polymeric flooring advertise a load capacity of up to 1200 pounds per square inch, meaning that very heavy loads can pass across the flooring without damaging the material.
• The only other method of effectively cleaning the wheels of carts is to spray down and wash them with anti-microbial disinfectants. This is a time-consuming method and will have varying results depending on the diligence of the cleanroom operator. Polymeric flooring has been shown to be 99.9% effective in some studies, so it might be considered a more efficient and ‘fail-safe’ way of ensuring the cleanliness of wheels than the washing method.

Health and Safety

Polymeric flooring can be easily cleaned using antimicrobial disinfectants, posing no health hazard to humans or the environment. It also eliminates the bending and tearing needed with peel-off mats.

It should be noted that polymeric flooring, while a slip-resistant surface, is slippery when wet and should be used where standing water is not an issue.

Environmental

Polymeric flooring is not subject to the same environmental concerns as peel-off mats. Polymeric flooring products avoid the waste of resources associated with manufacturing and disposing of adhesive peel-off mats. In some manufacturers’ cases, the flooring can be recycled upon completion of its service life.

In a facility using polymeric flooring in 10 locations, totalling 2,800 ft2, the kg of CO2 produced for the manufacture and disposal (incineration) of the flooring is just 4,620kg, compared to sticky mats 70,000 kilograms.

Should the polymeric floors be used in environments with hazardous substances, they can be easily cleaned using antimicrobial disinfectants, eliminating the costs associated with decontamination prior to disposal.

Convenience

Polymeric flooring needs to be professionally installed, and in some cases, the area may need to be closed for several hours to complete the installation. Once the polymeric flooring is installed, very little maintenance is required. As noted above, the floor has a life span of 3+ years, so it does not require constant replacement.

Polymeric flooring does need to be cleaned to remain effective. However, the cleaning schedule can be incorporated into the Standard Operating Procedures for floor cleaning in pharma.

While it may take longer to implement than peel-off mats, and cleaning may take longer than peeling a layer from a peel-off mat, the benefits outweigh the time invested in implementing and maintaining it.

Costs

The upfront cost of contamination control flooring can appear higher than peel-off mats. However, over the flooring’s 3-5-year lifespan, most facilities will see cost savings. In the example above, where a facility spends $9000 per annum on peel-off mats per location, switching to polymeric flooring would yield a return on investment in the first year.

Which floor system is best?

Whatever approaches are taken to control or mitigate microbiological floor-level contaminations, a good checklist to use includes the following:

• Is the method able to kill the organism in question?
• When applied, will the method achieve good and complete distribution on the floor?
• When applied, will the method achieve thorough and total penetration into cracks, crevices and other difficult-to-clean areas?
• When applied, will the method achieve sufficient contact time at a concentration to kill but not destroy equipment?

At Dycem, we offer innovative contamination control solutions designed to maintain the highest standards of cleanliness in critical environments. Our reusable mats, like our floating mats, and flooring systems, like CleanZone, effectively capture and retain particulates from shoes and wheels, significantly reducing the risk of contamination. With built-in antimicrobial protection, our products are effective and sustainable, making them a smart choice for any pharmaceutical facility committed to quality and safety.

Take Control of Floor-Level Contamination in Your Lab

Floor-level contamination in critical pharmaceutical manufacturing environments cannot be ignored, and implementing company-wide flooring options for reducing wheeled and foot traffic contamination has proven beneficial. Developing a strategy for implementing any option may utilize many company resources, but the benefits can be extremely valuable to product and personnel safety.

Don’t let floor-level contamination compromise your pharmaceutical manufacturing processes. Take action today to protect your products, personnel, and reputation. Explore our range of contamination control solutions and discover how our innovative flooring systems can significantly enhance your cleanroom’s integrity. Contact our team today and take the first step towards a cleaner, safer manufacturing environment.