Cleanroom personnel are a important source of cleanroom contamination. Almost all micro-organisms found in a cleanroom come from personnel, and they are also a major source of particles and fibres. It is therefore necessary to ensure the minimum of contamination is generated and transferred by personnel activities. By observing certain disciplines, contamination of the product can be minimised. These are discussed in this chapter.

When a cleanroom is about to be opened, management is faced with the task of employing people to work in the room, and determining what disciplines personnel (including maintenance and service technicians) should adhere to within the cleanroom. It is hoped that this chapter will assist in this task.

It should be noted that products manufactured in a cleanroom vary in their sensitivity to contamination, and cleanroom disciplines should reflect this. The information given in this chapter are options from which the user can choose methods that best reflect the degree of risk associated with their cleanroom.

People can, when walking, produce about 1 000 000 particles ³ 0.5 mm and several thousand microbe-carrying particles per minute. The more people, the higher the dispersion within the cleanroom. It is therefore important that the minimum of people, i.e. only the essential personnel are allowed into cleanrooms, and management should ensure that this is so.

Because many contamination problems are caused by lack of knowledge, only people trained to work in a cleanroom should be allowed within the cleanroom. Personnel should therefore be formally trained in the various aspects of contamination control. Visitors should be discouraged and only allowed in under the control of a supervisor; if a cleanroom is designed with windows for visitors to look into the cleanroom, this will usually suffice. Special care should be taken with service and maintenance technicians, and their tools and materials; this is discussed at the end of this chapter.

People who enter the cleanroom should not disperse significantly greater amounts of contamination than the normal population. Given below are examples of conditions that can cause more contamination than normal, and may therefore be unacceptable. Acceptability will depend on the risk, e.g. whether micro-organisms are a hazard, and whether the product is highly susceptible to contamination or not. It will therefore be up to management to decide which conditions are important.

The following suggestions contain criteria that can discriminate against some personnel. It should be ensured that any discrimination is neither illegal nor unfair. The list also contains a number of temporary conditions. These are included as they may be a reason for temporarily assigning personnel to a job outside the cleanroom.

• Skin conditions where unusually large amounts of skin cells are dispersed, such as dermatitis, sunburn or bad dandruff.

• Respiratory conditions such as coughing or sneezing caused by colds, flu or chronic lung disease.

• In a biocleanroom, it may be necessary to screen personnel for the carriage of micro-organisms that could grow in the product and cause spoilage or disease. Their suitability for work in a cleanroom should be considered with respect to the susceptibility of the product to specific types of microbial growth.

• People with allergic conditions, which cause sneezing, itching, scratching, or a running nose, may not be suitable for employment in a cleanroom. Sufferers from hay fever are likely to find relief in a cleanroom because the air filtration system will filter out the allergens responsible. Some people may be allergic to materials used in the cleanroom, such as (a) garments made from polyester, (b) plastic or latex gloves, (c) chemicals such as acids, solvents, cleaning agents and disinfectants, and (d) products manufactured in the room, e.g. antibiotics and hormones.

• Depending on the contamination risk within the cleanroom, some or all of the following suggestions should be brought to the attention of the staff so that contamination within the room may be minimised:

• Personnel should have a good level of personal hygiene. They should shower regularly and keep dandruff at bay. They should wash their hair after a haircut to prevent hair landing on the product. In the case of dry skin, they should use skin lotion to replace skin oil that is lacking; this should reduce dispersion.

• Materials such as cosmetics, talcum powder, hair sprays, nail polish, or similar materials are not normally allowed in a cleanrooms. Anything added on to the body should generally be considered a contaminant. Cosmetics are a particular problem in semiconductor manufacturing as they contain a large amount of inorganic ions such as titanium, iron, aluminium, calcium, barium, sodium and magnesium. In the photographic industry, iron and iodine ions give problems. Other industries, which do not have a problem with specific chemicals, may still experience problems as each application will deposit large numbers of particles (up to 10⁹ for particles ³ 0.5 mm) on the skin. Some of these will detach in the cleanroom.

• Watches and jewellery are normally not allowed in a cleanroom. If jewellery is allowed, it must be under the clothing and gloves. Rings can puncture gloves and harbour contamination under them. Personnel may be reluctant, for sentimental reasons, to remove their wedding or engagement rings. They may be allowed to keep them on if the skin under the rings, as well as the rings, is washed. Where the rings are liable to puncture the glove they should be taped over.

• Smokers are said to produce more particles from their mouth than the normal population and outgas chemicals from their body. It may be necessary to ensure that they have not smoked for several hours before entering the cleanroom. It has been reported that taking a drink of water before entering the cleanroom reduces the number of particles given off from the mouth.