The first Micronclean Handbook was published in 1981 and was revised and re-issued 10 years later as the ‘New Micronclean Handbook to Good Cleanroom Clothing Practice’. More than 10,000 copies have been distributed internationally.
Scheduled to be published early in 2012, the ‘Micronclean Big Blue Cleanroom Handbook’ is the latest edition and has been completely re-written to provide an up-to-date resource for anyone involved with any aspect of contamination control systems and controlled environments, covering topics such as cleanroom technology, clothing, cleaning and consumables procurement.
An excerpt from Section 7 of the handbook – “Cleanroom cleaning – methods and equipment” – can be found below.
To find out more about the Micronclean Big Blue Cleanroom Handbook please contact Micronclean at: bigblue@micronclean.co.uk
7.1 Contamination Control and the Requirement for Cleaning
A large amount of time, energy and money is usually expended on the design and development of contamination control facilities. Once the cleanroom is operational an equal emphasis is required to establish and maintain consistent ongoing control. The cleaning system is a key element of this process.
Cleaning can sometimes be regarded as a secondary function and may also be seen as an easy target for cost reduction exercises. However, without an efficient cleaning programme the whole cleanroom is at real risk of failure as contamination can quickly build up and pose a risk to products.
The cleanroom air filtration system effectively controls the ingress of airborne fibres and particulate into the cleanroom. However, this does not mean that the area will remain free from contamination during use.
Both the cleanroom staff and the production process will introduce a range of contaminants during operations.
7.2 Cleanroom Cleaning – General Considerations
A fully operational cleanroom may become contaminated by a range of materials. These can be either large visible contaminants, such as discarded packaging or visible liquid droplets, or microscopic particulates and fibres of approximately 50 µm or less, which are not visible in normal light.
Visible contaminants in the cleanroom can be controlled by basic cleaning and housekeeping methods.
Very large contaminants, such as discarded packaging or cleanroom disposables, can be placed in a disposal bag and carried from the area. Disposal containers should be placed in areas where they can be frequently emptied.
Reusable cleanroom clothing can be removed and placed in designated containers for collection and reprocessing.
Large visible particulates and fibres, usually deposited by gravity on horizontal surfaces, can be readily removed using cleanroom compatible vacuum cleaning, the material being lifted from the surface by the airflow and collected for disposal.
Removal of visible contamination is sometimes referred to as “cleaning” and the subsequent removal of microscopic particles as “decontamination” and this can be a helpful distinction during staff training.
Removal of microscopic contamination is achieved using specialised cleanroom cleaning materials and procedures. Microscopic contaminants include both viable and non-viable particles. This material will be deposited on horizontal surfaces but will also become attached to walls, ceilings and equipment.
The cleanroom airflow (vertical or horizontal unidirectional airflow or turbulent flow) will also affect the distribution and deposition of these particulates.
As part of the cleaning process it is often necessary to use antimicrobial chemicals
Microscopic particles and fibres on cleanroom surfaces may be attached by physical, chemical and electrical forces. Microscopic particles cannot be removed by dry vacuum cleaning as this method has insufficient energy to overcome these adhesive forces. This material must be dislodged by direct physical contact, which is usually achieved by mopping or wiping.
The materials used to make mopping or wiping products can affect their efficiency - the greater the contact area, the better the removal effect.
Particle removal is significantly improved if a liquid is used to aid the process, which allows some of the particle to surface bonding to be broken.
Suitable cleaning liquids not only increase the physical removal efficiency but may also dissolve or suspend the contaminants. Water, surfactants or solvents may all be used in this way to dampen wipes and mops and improve particle removal.
All surfaces in a cleanroom should be as smooth as possible with minimal sharp corners as rough surfaces and inaccessible angles are more likely to hold fine particles, making them difficult to remove.
As part of the cleaning process it is often necessary to use antimicrobial chemicals, which are used to kill or inactivate any micro-organisms remaining after cleaning. These are often referred to as disinfectants or sanitisers and are available in a wide range of formulations.
