Key steps to selecting cleanroom garments

| Cleanrooms and Contamination Control

Disposable cleanroom garments are made in different materials

DuPont explains how to strike the right balance between worker protection, comfort, and contamination prevention

Disposable protective garments are critical to safeguarding workers in cleanroom environments while preventing contamination. Steve Marnach, EMEA Training manager & Specialist Critical Environments at DuPont, examines the key factors to consider when selecting disposable garments.

Disposable vs reusable

Any protective garments designed to be disposed of or recycled after use can be defined as disposable. By contrast, reusable garments can be worn multiple times, washed, and repaired. There are situations where disposable clothing must be used and others where reusable garments are the best option.

Cleanroom garments are not only designed to prevent contamination in the surrounding environment. Unlike reusable clothing, come disposable garments are also classed as personal protective equipment (PPE) that is CE certified as category III, Type 5-B and 6-B (chemical and biological protective garments). As such, they are mandatory for cleanroom operations where the workers may be exposed to chemical or biological hazards (such as hormones, steroids, cytotoxins or other HPAPIs).

Another important difference between disposable and reusable clothing is that the latter must be washed by a professional cleanroom laundry. There are places in the world (particularly in remote areas), where there are not enough cleanrooms to justify the investment into a nearby cleanroom laundry. Also, for companies where only a handful of operatives work in the cleanroom, the logistical costs of washing cleanroom garments can be very high. In some facilities, the cleanroom is only operational on an irregular basis, so disposable garments will be less costly than a reusable alternative.

Likewise, there may be people entering cleanrooms occasionally, such as maintenance workers or inspectors. Here disposable garments are, once again, the best choice. Another good example is operatives handling liquids or substances that might stain their reusable cleanroom garments. To avoid having to change reusable garments, they often prefer to use disposable cleanroom coveralls and accessories which are then worn on top of the reusables.

Ultimately the choice between disposable and reusable will depend on the type of cleanroom application. Generally, it is a good quality risk management approach to keep a limited number of fully validated disposable cleanroom garments in stock. This will ensure you do not suddenly run out of garments if there is an issue with the cleanroom laundry.

Materials matter

There are three types of non-woven materials that are currently used to produce disposable cleanroom clothing: spunbound meltblown spunbound (SMS), microporous film (MPF) and Tyvek, which was first developed by DuPont. Each of these three materials has different properties.

The performance of SMS fabrics relies on a meltblown polypropylene layer between two open spunbound polypropylene layers. SMS fabrics tend to suffer from limited durability and have a relatively weak barrier performance. This is due to their “open” structure, which makes them a very comfortable material, but reduces their barrier against liquids and particles. Also, if they are abraded, these fabrics tend to leave fibers on the surface, and this increases the risk of particle shedding.

MPF is a bi-laminate material comprising a thin microporous film laminated to a spunbound polypropylene base layer. It offers limited durability since all barrier protection is lost when the protective film layer is abraded, leading to particle shedding. In addition, MPF’s low air-permeability makes it much less breathable than other fabrics, which results in poor wearer comfort and inferior heat control.

Tyvek is manufactured by a flash-spinning process of strong, continuous, high-density polyethylene filaments that are thermally bonded into a tight, homogeneous and soft fabric that is intrinsically breathable, with low-linting and strong barrier properties. This unique combination of barrier protection and inherent breathability makes Tyvek a highly optimised fabric for cleanroom, chemical and biological protective garments.

Breathability is key

Safeguarding the wellbeing of the wearer is critical to preventing worker fatigue, which may derive from poor clothing breathability and sweating. DuPont has run various studies and found that there are three key parameters to consider here: workplace conditions, work intensity and garment system.

In terms of workplace conditions, unlike many other work environments, cleanroom environments are always constant. In a grade A pharmaceutical cleanroom, the temperature should be below 21°C and the relative air humidity between 30% and 40% with constant controlled air changes. So, there shouldn’t be a problem with the ambient temperature. In terms of intensity of work, we all know the harder we work, the more we sweat. But this is generally not an issue in cleanrooms as operators have to move slowly to avoid creating air turbulence.

The garment system is, therefore, the most important factor to consider when it comes to worker comfort and wellbeing in cleanrooms. A typical cleanroom garment system consists of both under- and overgarments. Undergarments tend to be highly breathable polyester garments while overgarments can be either reusable, which are very breathable, or single-use, which are generally perceived as not being breathable. This is not always the case though, as our single-use cleanroom Tyvek IsoClean garments are breathable. They also exhibit good air permeability (tested following ISO 5636-5), a low thermal resistance (EN 31092/ISO 11092) and a low water vapor resistance (also EN 31092/ISO 11092).

Particle shedding

Particle shedding means how many of the particles shed by a worker will be kept inside the garment rather than go through and contaminate the environment. The most common way to evaluate particle shedding is the Helmke Drum test method. Most of the reusable and single-use clean and sterile cleanroom garments, such as our Tyvek IsoClean, achieve Category 1 in the Helmke Drum test, which is the best possible result.

Assessing the filtration efficiency of a cleanroom garment involves testing the particle filtration efficiency (PFE,) as per EN143, and the bacterial filtration efficiency (BFE), as per ASTM F2101. However, both are fabric tests only, not full garment tests. A more reliable testing method is the Body Box (as per IEST-RP-CC003.4). This simultaneously assesses particle shedding from the garment, particle shedding from an operative plus the filtration efficiencies of cleanroom garment systems. This is as close as you can get to real cleanroom operation conditions. Tyvek IsoClean garments display exceptional Body Box test results, even during knee bends.

The path to more sustainable clothing

Sustainability is becoming increasingly important when it comes to disposable cleanroom clothing. Although chemically or biologically contaminated garments cannot be recycled for obvious safety reasons, non-contaminated Tyvek garments can now be recycled.

DuPont has put in place fully operational recycle programs for non-contaminated Tyvek garments in both North and South America. The company is currently in the testing phase for setting up a similar recycling system in Europe.

Both reusable and disposable protective garments have a key role to play in cleanroom environments. Disposable clothing is the go-to solution for many cleanroom applications where high levels of worker protection and comfort go hand in hand with contamination prevention.

Jonathan Newell
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