The correct planning of personnel airlocks is a very important point in the overall concept of cleanroom production. What considerations should be made in advance?
1. why does a Cleanroom need a personnel airlock?
- to enable entry into a higher purity class without jeopardizing the process taking place in it
- for dressing and undressing staff
- for the entry and exit of persons
- for the storage and provision of cleanroom clothing
Humans are the greatest source of risk when it comes to introducing contaminants into Cleanroom. By far the highest proportion of foreign particles that can endanger production at Cleanroom enter Cleanroom with the staff. If employees or visitors enter a Cleanroom, it must be ensured that the cleanliness of the air in the Cleanroom is not jeopardized. In particular, the wearing of specific cleanroom clothing reduces the release of particles from people and street clothing.
There are therefore personnel airlocks between the outdoor area and Cleanroom, which serve as changing rooms and at the same time act as a barrier to carry as few particles as possible into Cleanroom.
2. determine lock size
Personnel airlocks must be set up in such a way that staff can dress and undress in a safe, ergonomic and time-saving manner. The airlocks are therefore equipped with cleanroom-specific furniture that is used to store clothing and that structures and facilitates the changing processes (e.g. washbasins, dispensers, lockers, sitovers, mirrors, waste bins).
When determining the size and set-up of a personnel airlock, a number of factors must be taken into account in advance. This means that, if possible, the deployment of personnel in the final configuration should be taken into account when planning the cleanroom.
The following questions should be considered at the planning stage:
- What is your clothing concept for the required cleanroom class?
- Which items of clothing should be put on where and in what order?
- Are there process-specific dress codes?
- What type of clothing is used (disposable/reusable)?
- How many people work at the same time per shift at Cleanroom?
- How many shifts are planned?
- Are there male and female employees? Can they use a shared changing area?
- Are personal lockers with locking facilities required?
- How should the newly packed garments be sorted? (size/ per employee)
- Would you like a washbasin in the airlock?
By answering these questions, the furnishings are arranged with dispenser systems to save space, so that only as much space as necessary is taken into account.
3. number of airlocks per cleanroom class
Particles are released or introduced into the personnel airlock during each induction process. These are “flushed out” with clean air during their stay. Airlocks in the transition from one cleanliness zone to the next should have the cleanroom class of the next room when not in use. This ensures that the next room is not endangered when access is granted after the airlock purge time.
The number of personnel airlocks required for safe entry therefore depends on the required cleanroom class. Several personnel airlocks are recommended for higher cleanroom classes:
| Cleanroom class | ISO 8 | ISO 7 | ISO 6 | ISO 5 | GMP D | GMP C | GMP A/B |
| Number of personnel locks | 1 | 1 | 2 | 3 | 1 | 2 | 3 |
In some cases, the airlocks are also combined with air showers, as these are intended to practically replace an airlock.
4. pressure cascades
To prevent contamination, the following technical precautions must be taken in a cleanroom operation:
- Prevention of uncontrolled air flow in the Cleanroom
- Avoidance of pressure drop
The airlocks are used to maintain so-called pressure cascades. Pressure differences between the outer area, the airlocks and the Cleanroom prevent particle movement into the cleaner zones. For higher purity requirements, zones with several pressure levels are formed in order to protect the most sensitive zones the most.
Pressure differences of 5-20 Pascal (according to ISO 14644-4) or 5-15 Pascal (according to GMP Annex 1) between the different cleanroom classes ensure a targeted flow of air. In order to maintain the pressure cascades, the airlock doors are interlocked on both sides. This interlocking ensures that only one of the two doors can be opened at a time to prevent a sudden loss of pressure.
The pressure zones are selected for the rooms with control tolerances in such a way that the control system can ensure that no pressure reversal can occur.
