Cleanroom Entry & Exit Procedures
By Bill Whyte,
University of Glasgow
Personnel working in cleanrooms disperse large quantities of particles from their skin and clothing. It is therefore necessary for personnel working within a cleanroom to don clothing that will minimize this dispersion.
Cleanroom clothing is made from fabrics that do not lint or disperse particles and act as a filter against particles dispersed from the person's skin and indoor, or factory, clothing. The type of clothing used in a cleanroom varies according to the type of cleanroom. In cleanrooms where contamination control is very important personnel wear clothing that completely envelopes them to ensure that particles and bacteria are not dispersed into the air, i.e., coverall, hood, facemask, knee length boots and gloves. In cleanrooms where contamination is not as critical, then a smock, cap and shoe covers may be sufficient. Whatever the choice of fabric or style of clothing, garments will have to be donned prior to entering the cleanroom. This should be done in such a manner that the outside of the clothing is not contaminated. This article describes such a method.
The majority of cleanrooms require that a garment be used more than once. It is therefore necessary to devise a method that ensures garments are removed and then stored in such a way ensure the minimum contamination.
It is necessary to change into cleanroom garments before entering a cleanroom. The method outlined here can be used in a typical cleanroom. It should be noted that there are alternatives to the proposed method and these are quite acceptable as long as they give an appropriate level of contamination control. It is common to find that the change area is divided into three zones, or areas. These zones are pre-change zone, changing zone, and clean-room entrance. Personnel move through the zones carrying out the changing procedure in the following manner.
Before changing clothing, it is best to blow the nose and go to the bathroom. It is impossible to correctly blow a nose in a cleanroom. If it is necessary to come out of the cleanroom to go to the bathroom this is likely to entail changing in and out of cleanroom clothing.
In cleanrooms where outdoor shoes are not removed or fully covered, shoe cleaners should be used. These shoe cleaners are specially made for cleanrooms. Cleanroom mats or flooring are often used in the approach route to the pre- change room. The shoes should be applied to a mat three times to ensure the removal of practically all footwear contamination. Cleanroom flooring should be of sufficient size for the correct number of steps (a minimum of three).
Within the pre-change zone, the following tasks may be carried out:
1. Personnel should remove sufficient street or factory clothes to feel comfortable in the cleanroom. If the company provides dedicated cleanroom garments for wearing under the cleanroom garments, then all street clothing should be removed and replaced.
2. Watches and rings should be removed. Wedding rings that are smooth may be acceptable if the ring (and under the ring) is kept clean. Rings that are not smooth can be taped over. Along with other items, such as cigarettes and lighters, wallets and any other valuable should be securely stores.
3. Remove cosmetics and, if required, apply a suitable skin lotion. Don a disposable bouffant hat or hairnet to ensure that hair will not stick out from under the cleanroom hood. Put on a beard cover, if appropriate.
4. Put on a pair of disposable footwear coverings, or change into cleanroom-dedicated footwear.
5. If a hand-washing system is located in this area, then wash the hands, dry and apply a suitable hand lotion. In bio-clean areas, it will be necessary to wash the hands in a suitable skin disinfectant, however it is probably best that the hands be washed within the change area just before the clean garments are put on.
6. Cross over from the pre-entry area into the changing area or zone. The demarcation between these two zones may be a door or a crossover bench, or both. The bench will normally be built between the zones to ensure that personnel cannot walk round it but must cross over it. If a bench is used, it may be best to attend to footwear as one crosses over it. If a bench is not used, then a cleanroom mat or flooring can be used.
The outer cleanroom garments are put on in this area. Several methods can be used but the following one is used in many cleanrooms. This method assumes that a facemask, hood, coverall and overboots are used but it can be adapted for use with a cap, gown and overshoes. This method requires that the garments be donned from the top down.
7. The garments to be worn are selected. If a fresh garment is used then it should be checked for size and the packaging checked to see that it is free from tears and faulty heat seals. The packing is then opened.
8. If a hand washing system is installed in this area, then the hands should now be washed (and disinfected if required). This is probably the best time to wash hands; temporary gloves known as "donning gloves" are sometimes used. Use of these gloves is confined to the highest quality of cleanroom. These should be put on, if required.
9. A facemask and hoot (or cap) should be put on. It appears to make little difference whether the mask is put under, or over, the hood. However the mask should be placed under the nose.
10. The coverall (or gown) should be unfolded without touching the floor. The garment should then be put on ensuring that it does not touch the floor. It is sometimes possible to get the cleanroom laundry to fold the garment in way that will minimize the chances of the garment touching the floor. If this cannot be done, or it is uneconomical, then the following methods can be considered. A) The coverall can be gathered together at the four corners, i.e., the two wrists and the two ankles. It should then be possible to put on one leg and then the other without touching the floor. B) The garment can be held in the inside at waist level, some of the material gathered up and one leg, and then the other, put into the legs. The top of the coverall can then be slipped over the shoulders. C) The left cuff and the left zipper can be taken in the left hand and the right zipper and the right cuff in the right hand. The coverall can then be gathered up at the waist and one leg placed into the garment and the other leg into the other. By releasing one cuff at a time, first one arm and then the other can then be placed into the garment.
11. The garment should then be zipped all the way up to the top, with the yoke of the hood (if used) being tucked inside the collar.
12. If the garment has snaps at the ankles and wrists, then these should be snapped shut.
If a crossover bench is available, it should be crossed over now. This bench is used to demarcate the slightly soiled changing zone from the cleaner entrance zone and allows cleanroom footwear (overshoes or overboots) to be correctly put on.
13. Personnel should sit on the bench. One leg should be raised, the cleanroom footwear put on, the leg transferred over the bench and placed on the floor of the entrance zone. Footwear should be put on the other foot and the leg taken over the bench. While still sitting on the bench, the legs of the cleanroom garment and the footwear should be adjusted for comfort and security. Personnel should now stand up.
14. If donning gloves have been used they can be dispensed with now; if deemed necessary, the hands can again be washed (or disinfected).
15. Powder-free cleanroom gloves should now be put on. A method should be employed to prevent the outside of them from becoming contaminated when being put on. This usually entails holding the glove at the cuff.
16. Protective eyeglasses, if required may be put on.
17. The garment should be checked in a full-length mirror to see that it is being worn correctly.
18. Personnel may now proceed into the cleanroom. This may be over a cleanroom mat.
Exit changing procedures
When leaving a cleanroom personnel will either a) discard all their garments and disposable items: on re-entry they will use a freshly processed set of garments this method is normally only used in a pharmaceutical cleanroom or b) discard their disposable items, such as their mask and gloves, but reuse their garments on re-entry.
If a complete change of clothing is required on re-entry, then the disposable bouffant hat, gloves, facemask, and if disposable shoecovers will be placed in a separate container for dispatch to the cleanroom laundry for processing.
If the garments are to be used again on re-entry, they should be removed in such a way that the outside of the garment is contaminated as little as possible. The cleanroom footwear should be removed at the crossover bench, one at a time, and the inner shoe (with or without the covering of a plastic shoecover) placed in the less clean zone. The coverall should be unzipped and removed using the hands within the garment to remove it over the shoulder and down to the waist. In a sitting position, one leg is now removed from the garment. The empty arm and leg of the garment should be held so that they do not touch the floor. The other leg can now be removed. The facemask and hood can now be removed.
Garments to be used again on re-entry should be correctly stored. This can be done in several ways. These are as follows:
- Each item of clothing can be rolled up ensuring the inside does not touch the outside. In the case of cleanroom footwear, this should be done so that the dirty soles are to the outside. The footwear can now be placed in one open compartment and the hood and coverall (or cap and gown) in another. If thought necessary, the items of clothing can be placed into bags before being put in an open compartment.
- The hood (or cap) can be attached to the outside of the coverall (or gown) by means of a snap, and hung in a cabinet. The cleanroom footwear can be placed at the bottom of the cabinet. Garments can also be hung up in the room but they should not touch the wall, or each other. In higher-grade cleanrooms, clothing is often hung up in unidirectional flow cabinets (normally vertical flow type), specifically made to ensure that garments are not contaminated.
- Garment bags, which can be hung up, can be used. These will have separate pockets for the various clothing items and should be regularly laundered.
If the above entry and exit methods are used in a cleanroom facility then contamination of garments during donning will be minimized. However, because of the layout of particular change areas it may be necessary to modify the method suggested above. If an alternate method can be devised to minimize contamination then no harm will be done to the product.
When a final procedure is devised, it is often a good idea to have the procedure printed and displayed in the change area. This assists the changing and when changes are accidentally introduced (or deliberately to cut corners) then reference to the correct procedure will be definitive in any discussion between management and personnel.
Acknowledgement: This article is based on the information given in a set of procedures written by the author for the Scottish Society for Contamination Control. Their assistance is acknowledged.
Bill Whyte is a Research Fellow in the Mechanical Engineering Department at Glasgow University in Scotland. He has been involved with cleanrooms for over 30 years and has published over 100 papers and reports on this subject.