Cleanrooms: Controlled environments

Employees in cleanrooms wear cleanroom garments. This entails that cleanroom staff wear, completely sterile disposable clothing or sterile reusable clothing in sterile environments.

Sterilisation, wearing and laundering may affect the physical and functional properties of reusable cleanroom garments. Also, fibers can be shed and polymers that make up the garments can be damaged at the molecular level. Routine visual inspections are often used to evaluate garment quality. However, changes in some properties are not visible to the naked eye.

These features, which are not visible to the naked eye, should be included in the decision making process when reusable clothing should be phased out. For new cleanroom garments, information on physical properties is available. In contrast, far less data is available over the entire lifecycle. DuPont has been researching the physical properties of reusable garments after a certain number of cycles of sterilisation to help select cleanroom garments.

Method

Two pattern of reusable garments made of polyester fabric with integrated carbon fibers to dissipate electrostatic charges were used for the tests. These were divided into A and B. After determining 30 cycles of laundering and gamma irradiation, the garments were tested (Figure 1).

Important findings

The data from the tests shows that the properties of clothing change after a certain number of cycles of laundering and sterilisation (gamma irradiation). With the naked eye, these changes are not always visible. A single visual inspection is therefore not sufficient for material verification.

Recommendations based on the tests:

• Consider the performance data over the entire life cycle.
• Enact test protocols to monitor performance of garments as they age, based on the risk assessments and need of cash individual cleanroom.
• Establish criteria as to when the protective clothing will be taken out of service if it no longer fulfills the functional requirements

For details on the procedure and the tests, see the PDF document DuPont: Controlled environments.