The following suggestions should be considered to ensure that personnel do not contribute to the contamination within the room:

1. Silly behaviour should not be allowed. The generation of contamination is proportional to activity (Figure 1). A motionless person can generate about 100 000 particles ³ 0.5 mm/min. A person with head, arms and body moving can generate about 1 000 000 particles & 0.5 mm/min. A person who is walking can generate about 5 000 000 particles ³ 0.5 mm/min. Personnel who move quickly passed products may cause a disturbance of the air that leads to contamination.

   

   Figure 1. Particle dispersion in relation to movement

2. Personnel should position themselves correctly with respect to the product, so that contamination does not land on it . They should not lean over the product in such a way that particles, fibres or microbe-carrying particles, fall from personnel onto the product. If personnel are working in a flow of unidirectional air, they should make sure that they are not between the product and the source of the clean air, i.e. the air filter. If they are, a shower of particles could deposit on the product. Methods of working should be pre-planned to minimise this type of contamination.
   
   
3. Consideration must be given as to how products are moved or manipulated. 'No-touch' techniques should be devised to prevent contamination getting from the gloved hand onto the product. Although gloves are worn in cleanrooms, they are still likely to be a source of contamination (although a reduced one). An example of this 'no touch' technique is the use of long forceps rather than hands to grip materials
   
   
4. Each cleanroom should have its own 'no-touch' rules to ensure that the product is not contaminated.
   
   
5. Oil and skin particles would contaminate the wafer with catastrophic results. If the wafer is held around the edge of the wafer then contamination is reduced, but can still get onto the surface.
   
   
6. Use of a glove will reduce contamination yet further, and this technique is still used where the line widths are large and a lower yield acceptable.
   
   
7. In semiconductor facilities, wafers will be handled with a vacuum wand which attaches itself to the back of the wafer . Robotic manipulation can also minimise contamination.
   
   
8. Personnel should not support material against their body . Although they will be wearing cleanroom clothing, which is much cleaner than indoor or factory clothing, it is not contamination free. Particles, fibres and micro-organisms can be transferred onto the items carried.
   
   
9. Personnel should not talk when working over the product, or spittle from the mouth will pass round the imperfect seal between the mask and the skin and contaminate the product . Talking, coughing or sneezing can release contamination from the mask surface. If personnel cough or sneeze, they must turn their head away from the product. Masks are often replaced after sneezing. Masks must not be worn below the nose but over the nose as large particles can be released from the nose when snorting.
   
   
   
10. It is generally not good practice for personnel to touch cleanroom surfaces. Although cleanroom surfaces are very much cleaner than those outside the cleanroom, its surfaces, and that of the machinery in the room, will have particles, fibres and bacteria on them. If personnel touch their garments or mask, they also will pick up contamination on their gloves, which may be transferred to the product. Hands grasped together in front of the personnel, in the style of a hospital surgeon, will help to ensure that they do not inadvertently touch surfaces.
    
    
11. Personal handkerchiefs should not be brought into cleanrooms . These are clearly a major source of contamination and will transfer particles and microbe-carrying particles into the air and onto gloves. Noses should not be blown inside a cleanroom. The change area may be an acceptable alternative.
    
    
12. Washing, or disinfection when required, of gloves during use should be considered. Glove washing can be used in cleanrooms where products are handled and there are particular difficulties in keeping gloves clean. For example, in aseptic pharmaceutical production areas, gloved hands are rinsed with a suitable disinfectant (70% ethanol or iso-propanol) at regular intervals and prior to starting a critical operation. Alcohols are particularly useful, as they do not leave a residue on the glove.