Medical Device Link.

MANUFACTURING

Continuing cleanliness

When a medical device company identifies the need for a clean room, much time, thought and effort go into planning and designing the room, and determining the classification needed and which air filters are required to achieve this standard. But how much thought goes into maintaining the cleanliness of the room thereafter? Once the room is installed and operational, the air filters alone will not ensure that the room maintains its cleanliness. Stringent cleaning measures must also be taken.

There is a wide range of cleaning products on the market, but how does a company determine what is best for it, particularly if it has little prior experience of clean rooms? As a starting point, the company needs to define “clean:” does the room need to be clean, sanitised or sterile?

For a clean room to be clean, not only does the visible dirt need to be removed, but also any contaminants that could have a detrimental effect on the products or materials being worked on. For example, hard particles such as paint, concrete or metal can cause damage to the surface of the product they come into contact with and soft particles such as skin, hair and clothing can interfere with the operation of the device.

Determine acceptable contamination

Different parts of the clean room will be dirtier than others. These areas can be classified as “critical,” “general” and “outside.” For example, surfaces that have more contact from people will be dirtier than those that do not, that is, floors and doors will be dirtier than ceilings and walls. Those high-contact areas will be classified as critical. Once this has been determined, acceptable or tolerable levels of contaminants can then be agreed.

Distinction needs to be made between disinfecting, sanitising or treating with antistatic solutions. There are many different products available, each having a different purpose and level of effectiveness. As a starting point, a vacuum cleaner is effective at picking up larger particles, but an alternative method will be required for particles of 10 μm or smaller. Wet mops, dry wipes with liquid or impregnated wipes are effective because they attract smaller particles. However, there are disadvantages to wipes. Reusable wipes and mops tend to shed the least, but are the most absorbent. Conversely, highly absorbent disposable wipes and mops also tend to shed more. Tacky wipes can be used on smooth or glazed surfaces. These are generally solvent free, which reduces the risk of fumes and resistance build up in bacterial organisms.

Select the cleaning agents

Table I. (click to enlarge) Considerations for choosing an appropriate cleaning agent.

When choosing cleaning agents, consideration needs to be given to the results required, the surfaces being cleaned, other chemicals being used, timescale and temperature (Table I). All of these decisions will be determined by the devices being manufactured.

Detergents are used to remove dirt, grease and soil. These will not necessarily kill bacteria, viruses, mould or fungi; therefore, additional products will be required.

Disinfectants reduce or kill bacteria and should only be used on clean surfaces; that is, those that are free from dirt, grease and soil. Many contain other chemicals to assist in the cleaning process, for example, surfactants to control foaming and to improve the wetting properties or alcohol to increase the drying time of the product. They are effective at fighting disease-causing microbes but will not kill spores. Sanitisers act as a detergent and a disinfectant combined.

Antibacterial cleaners will only kill bacteria; antimicrobials will kill bacteria, viruses and moulds; sporicides will kill microbial spores, especially bacterial spores and microbial spores.

Consider consistency

To ensure consistency in cleaning products, diluted disinfectants and detergents (unless sterile) should only be stored for a defined period of time. In clean rooms of grades A and B, disinfectants and detergents must be sterile. These products should be rotated regularly to ensure resistant strains do not develop and regular checks should be undertaken. Clean-room management will need to determine the frequency that rotation takes place and whether to use one or more supplier. If static is an issue, nonionic or cationic detergents diluted with water are suitable. If using alcohol as a sanitiser, consideration needs to be given to the contact time. Alcohols generally evaporate in less than 30 seconds and it may also be necessary to use a microbial inhibitor.

For floors and walls, phenols and quats are generally used; they tend to be avoided on other surfaces because they can be corrosive. Best practice recommends rotating these products regularly to reduce the risk of developing resistant strains of micro-organisms. Care should be taken, however, because soaps and anionic detergents can inactivate quats.

Purchasing decisions may also be influenced by the contact time of the cleaning product. Some products work more effectively if left on a surface for a given length of time. This will not present problems on horizontal surfaces, but may prove difficult on vertical surfaces. Some disinfectants work better at higher temperatures, which will influence the contact time needed. If it is not possible to alter the ambient temperature of a room, the contact time may need to be altered. If a longer contact time is not possible because of operational time constraints, the concentration of the disinfectant can be increased to improve its bactericidal activity. However, the cost implication of this should also be borne in mind.

In addition to the above, the clean-room manager needs to be confident that the products used meet other criteria:

• Has it been through a validated sterilisation process?
• Has it been manufactured under good manufacturing practices?
• How stable is the product?
• What is its shelf life?
• Does the product come with batch certification and traceability?

Follow a good routine

Establishing a cleaning routine will help achieve the best results. General guidelines suggest cleaning from the dirtiest areas to the cleanest and beginning with the highest classification area/room. In a vertical laminar flow room, the room should be cleaned from top to bottom, and a horizontal flow room should be cleaned from back to front. To ensure that all areas are cleaned and none missed, a grid approach is often used. The room can be split into manageable squares of, for example, 30 m². Care should be taken to ensure that all cleaning is done in straight horizontal lines, each one overlapping the previous one by 10–20%, and never in a circular motion.

Establishing and adhering to a well-prepared cleaning programme will considerably help to ensure that the clean room operates to the highest standard. After all, the return on the investment made in setting up the clean room should not be reduced by an inferior cleaning routine.

Joe Govier is Managing Director of Cleanroomshop.com and Connect 2 Cleanrooms Ltd, 1 Willow Mill, Fell View, Caton, Lancaster LA2 9RA, UK, tel. +44 1524 771 923, e-mail: joe.govier@connect2cleanrooms.com, www.connect2cleanrooms.com, www.cleanroomshop.com.