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Normal industrial practice is to control foot-borne contamination with adhesive peel-off disposable mats, but polymeric contamination-control flooring is becoming increasingly popular.
Controlling particulate contamination is essential in pharmaceutical cleanrooms. Operators are particularly concerned with particles of 10 µm or smaller, which are mainly invisible to the naked eye, occur in differing shapes, and derive from various sources. These particles include human hairs (i.e., 50–150 µm), dust (i.e., 1–100 µm), and bacteria (0.5–10 µm). Particles larger than 40 µm generally can be seen by the human eye. Pharmaceutical companies are particularly worried about particle sizes between 0.5 and 5 µm.
Human operators are a major source of contamination. The body’s regenerative processes (e.g., shedding skin, oils, and hair), behavior (e.g., movement, sneezing, and coughing), and attitude (e.g., work habits and communication) all contribute to contamination. Employees’ activity rapidly accelerates the rate at which particles are generated. The control of particulate contamination from personnel movement thus is a crucial factor in manufacturing operations undertaken under cleanroom conditions. If unchecked, human contamination could affect product yield, productivity, a company’s costs, and product quality.
Large numbers of viable and nonviable particulates are carried on operators’ feet or on cart wheels. The systematic removal of foot-borne small particulates is essential. Normal industrial practice is to control foot-borne contamination with adhesive peel-off disposable mats, but polymeric contamination-control flooring, such as CleanZone Technology from Dycem (Bristol, UK) is now a more popular choice.
Peel-off mats are made up of multiple sheets of polyethylene film coated with acrylic adhesive that traps particles. Operators rip up and dispose of peel-off sheets when they are dirty, which typically occurs several times during a shift. This process frequently sheds entrapped particles, however, thus greatly reducing the mats’ effectiveness.
Polymeric products are made from a blend of pure polymeric compounds and have a three- to five-year life cycle. When a polymeric surface becomes dirty, operators can clean it with a sponge and a mop with detergent. Finally, operators can dry the surface with a squeegee. This quick cleaning process can be incorporated into the facility’s regular wet-clean cycle.
Control of foot- and wheel-borne contamination
Polymeric flooring and peel-off mats reduce contamination by particles larger than 25 µm at roughly similar rates (i.e., 80–95%). On the other hand, polymeric flooring can be two to five times more effective than peel-off mats at reducing contamination from particulates of 10 µm and smaller.
A typical peel-off mat has a coating of acrylic adhesive that is less than 10 µm thick. Particles larger than 10 µm tend to stick to the adhesive and prevent smaller particles from contacting and sticking to the coating. In contrast, the polymeric surface of contamination-control flooring allows contact with all particle sizes. It thus collects and contains more than 99% of particles between the sizes of 0.2 and 100 µm. Therefore, polymeric flooring can control viable, biologically active particulates under circumstances where adhesive peel-off mats can be ineffective.
Polymeric flooring also removes particulates over a much larger control area than adhesive peel-off mats do. The polymeric flooring’s electrostatic forces enable it to attract and contain airborne particles above its surface, as well as trapping particles through foot and wheel contact.
Several groups have compared the efficiency of polymeric products and disposable mats. For example, GlaxoSmithKline (London) reported that polymeric flooring effectively prevented 99.9% of viable and nonviable foot- and wheel-borne particulates from entering a critical area. In contrast, peel-off mats prevented 27% of this contamination from entering the area (1). These results indicate that polymeric flooring can be an effective means of controlling foot and wheel-borne contamination, thereby reducing the number of microorganisms entering critical environments.
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Costs and environmental considerations
In addition to their efficiency at reducing contamination, cleanroom operators must also consider the operating costs that their solutions entail. Table I shows that cost savings can be achieved over the service life of polymeric flooring, compared with peel-off mats (2).
In addition, cleanroom operators increasingly seek to reduce the environmental effect of their operations. At the end of its service life, a peel-off mat generates an eight-inch ball of consumable waste that usually is disposed of in a landfill. On completion of their service life, the polymeric flooring products may be readily recycled for less crucial uses. Table I shows a comparison of the environmental effects of peel-off mats and polymeric flooring.
Peel-off mats had been the preferred method of controlling foot- and wheel-borne contamination in pharmaceutical cleanrooms for some time. Now, polymeric flooring’s comparatively greater efficiency at controlling small particles, coupled with environmental and cost considerations, has made it the solution of choice. Cleanroom operators must weigh various factors when choosing contamination-control products. Selecting the appropriate solution can help improve a facility’s productivity and reduce its costs.
1. G. Prout, Eur. J. Parenter. Sci.14 (1), 13–18 (2009).
2. C. Clibbon, Eur. J. Parenter. Sci.7 (1), 13–15 (2002).
Gerry Prout is managing director at Kennet Bioservices and Kennet Coacs, 6 Kingsdown Orchard, Hyde Road, Swindon, SN2 7RR, UK, tel. +44 0 7774 965265, [email protected]