INDUSTRY CLEANROOM WHAT IS A CLEANROOM? A cleanroom is an environment with a controlled level of pollutants such as dust, airborne microbes, aerosols (gas with particles) and chemical vapours. The pollution level is specified as the number of particles larger than 0.5 micrometres (abbreviated as μm = one millionth of a metre) per cubic metre of air. A hair is approximately 100 micrometres (μm), so the particles we are talking about are extremely small. To provide further perspective, normal outdoor air in an urban environment contains approx. 35,000,000 particles larger than 0.5 micrometres (μm) while a cleanroom of ISO class 3 is permitted to contain no more than 35 particles of the same size. WHY DOES A CLEANROOM NEED TO BE SO CLEAN AND HOW IS THIS ACHIEVED? After World War II technical development underwent significant expansion, but this was soon accompanied by problems. Aircraft flew off course, computers lost memory, hospital infections increased and road traffic sometimes came to a standstill because the traffic lights refused to change from red to green. It was discovered that the cause of this was the pollutants built in during the manufacture of technical equipment and medical devices. The smaller the components people tried to use, the worse the problem got. The first cleanrooms were built in the 1960s, and with the aid of a constant flow of air filtered through what is known as a HEPA (high-efficiency particulate air) filter, it was possible to successfully lower and control particle levels in a very effective manner. KEEPING AN EMPTY ROOM CLEAN IS NOT THE BIGGEST CHALLENGE. The problems start when you put equipment into the room – and people to handle the equipment. People give off hundreds of thousands of particles in the form of skin cells, micro-organisms and hair, and for every minute that goes by, and the more we move, the more particles we give off. In practice, this requires putting filters around the human body to prevent particles from entering the air. Fristads has manufactured clothing for cleanrooms and controlled environments since 1996. ISO CLASS 1 2 3 4 5 6 7 8 9 MAX. NUMBER OF PARTICLES PER M3 > 0.5 µm 0.35 3.5 35 352 3 520 35 200 352 000 3 520 000 35 200 000 (normal room air) ISO CLASS 3 Suit recommendations: Hood Hair cap Coverall Underwear Boots Face mask Gloves Change interval: Each time cleanroom is entered ISO CLASS 5 Suit recommendations: Hood Hair cap Coverall Underwear Boots Face mask Gloves Change interval: Every day ISO CLASS 7 Suit recommendations: Hair cap Coat Shoe protectors Face mask Gloves Change interval: Twice a week ISO CLASS 4 Suit recommendations: Hood Hair cap Coverall Underwear Boots Face mask Gloves Change interval: Each time cleanroom is entered ISO CLASS 6 Suit recommendations: Hood or hair cap Coverall or coat Boots or shoe protectors Face mask Gloves Change interval: Twice a week ISO CLASS 8 Suit recommendations: Hair cap Coat Shoe protectors Face mask Gloves Change interval: Twice a week THIS IS WHY WE ONLY USE SYNTHETIC FIBRES Workwear for cleanrooms must not give off particles or fibres. Cotton and other natural materials are woven from short fibres that detach easily and are therefore unsuitable. Cleanroom clothes consist of synthetic fibres – filament polyester, i.e. endless fibres. THE FRISTADS ”BOUND SEAM” Our bound seam is a refined version of the standard bound. It is more impermeable because the hem is like a hood. It is stronger because double rows of stitches each pass through six layers of fabric. It is safer because the carbon filaments woven into the hem produce good electrostatic discharge, even after repeated washes. 123
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