The primary sources of cleanroom contamination are through equipment, Room structure and materials, improper ventilation, and the most important factor People. People ie. Personnel of a pharma factory are the largest sources of contamination in any pharmaceutical facility. It is for these reasons all major guidelines and regulatory bodies recommend using safe mechanisms of material transfer from one area ensuring Air- Borne contamination is controlled. This is the premise where Passboxes are the silent Heros of any pharma facility.
Pass boxes play a supercritical role when it comes to Material transfer from an area of one classification to the other. They help avoid cross-contamination between two areas thereby maintaining the integrity of the cleanroom systems. The material used for constructing Pass boxes is SS304 or SS316 or SS316L. Some regions also refer to Pass boxes as Pass-Thru Hatches, Pass-through Windows, or Transfer Hatches. There are 2 basic types of pass boxes
Static Pass box
- Fitted only between two cleanroom areas of the same classification levels and has no Ventilation ( air supply or extract) provision.
- It is also known as a passive pass box and is equipped with UV Light It’s mainly used for non-complex, quick transfers of products in the same classification of Air.
Dynamic Pass box
- Fitted between clean room areas of different classification levels and Material is passed through vertically HEPA filtered air.
- Also called Active Pass Box and they are too equipped with UV light
- If a Dynamic Passbox is fitted with a Vapourized Hydrogen Peroxide Generator ( VHP) as a decontamination system it may also be called a Bio De-Contamination Pass Box.
What’s UV Light Got to Do Here?
Ultra Violet light is Anti-Microbial and germicidal. The 240-280 nm wavelength UV light destroys the DNA of Pathogens.
Common Features in both types of pass boxes
Yes, the title talks differences but we have to tell you the similarities first :
- Interlocked doors ( ensuring only door opens at a time)
- UV lights & Fluorescent / Visible lamps. ( yes there are two switches)
- These could be 2 door or 3 door pass boxes.
- UV light Hour meter ( the light switches off when either of the doors are open) these lamps are advised to be replaced after 3000 hours- Some would say 1000 )
- Completely Airtight.
- They can be Floor Mounted as well as Wall Mounted.
- Door Release Switch on either side.
- Internal Covings for easy cleaning.
- Both are cleaned with Disinfectants (70% IPA ) from time to time.
While both types of pass boxes are used for material transfers the differences between them could be identified by the conditions in which they are employed. Check out the differences between them below:
Material Transfer and Room Air Classification
A dynamic pass box is used to transfer the material between non-classified areas to classified areas or between two classified areas with a class difference. Static pass box is used to transfer the material between two equally classified areas. So Transfering material from Class D ( ISO 8) to Class C ( ISO 7) would require a Dynamic Pass-Through Hatch whereas Transfering Material from one Class D ( ISO 8) to another Class D ( ISO 8 ) area would be fine with a static pass box.
If we were to send materials from a warehouse into a processing area which pass box would you use?
If we were to send samples to the IPQC room which Pass box would you use?
Are they the same class?
Air Circulation System and Velocity
A Motor-blower with suspension arrangement for reduced noise levels (Less than 67 dB) is provided for Dynamic Pass Boxes. A Dynamic Pass box also acts as an ISO 5 ( Class A ) Airlock which could be any of the 3 airlock types Bubble, Cascade, and Sink. In a dynamic pass box laminar air passed through HEPA EU14 filters (99.997% efficiency down to 0.3 Micron) at an average velocity of 0.45 m/s is passed over the material. Dynamic Pass boxes have a perforation at the bottom to enable air circulation. No such arrangements are necessary for a Static Pass box.
The Validation protocols and procedures for Dynamic Pass Boxes are hence more stringent and elaborate with HEPA Integrity Tests, Air Velocity Test and recovery tests as per ISO -14644-3 as compared to the validation of Static or Passive Pass boxes
As we understand that the Dynamic Pass Box Model needs HEPA filtered air the arrangement and the additional space occupied lead to the added cost, however in transfers between two differently classed areas, the investment is totally worth it for the compliance benefits it provides. Do not make the mistake of providing a static pass box where the situation demands Dynamic , the non compliance is usually grave and unexplainable to the auditors.
Timers and Transfer protocol
Dynamic Passboxes have a clean down timer with operation Hold Indicator interlock to put on fluorescent lights only after clean down time is over. The Transfer mechanism of different products could depend on the usage, however, it is a given that the material being transferred has to spend a minimum amount of residence time ( Eg. 2 -5 mins) inside the chambers so that the contamination causes are overcome and higher air classification is achieved inside the Box. There is a certain amount of time after which UV lights must be turned on for effective disinfection of the microbes and then turned off before the cabinets are to be opened from the other side. For static pass-throughs, the residence time is limited only to material disinfection done by the UV Lamp and shall be lower than dynamic pass box residence time.
there’s so much science behind a simple box, ask a QC pharmacist to share with you the Standard Operating Procedures and you shall know the various steps involved in using one of these static or dynamic pass boxes or reach out to us at email@example.com and we shall have it emailed to you.