Cross Over from Class III BSC to High Containment Gloveboxes

High containment gloveboxes (HCG) have been used in the pharmaceutical industry for containment of potent compounds, along with providing specific environmental conditions, for years. These types of glovebox design fit well into the Class III Bio Safety Cabinet classifications but provide even better environmental attributes than the standard BSC designs.

If you review the classification design requirements provided in the table, you will notice that the BCS III design parameters actually describe a typical high containment glovebox. They are totally enclosed, HEPA filtered, and the operator utilizes gloveports for manipulation of pathogens. In a high containment glovebox, you have the same parameters but are working with potent compounds and not biohazardous materials.

In order to achieve what you need to with regard to choosing any type of environmentally controlled device, you need to first identify and assess the process. Then you can compare a HCG with a BSC cabinet and make the comparison between the two.

HCG has added benefits over a typical BSC cabinet:

• HCG designs are more robust, and they have a once through airflow requirement and do not recirculate. So everything in the glovebox is not “re-contaminated.”
• Relative humidity can be controlled with a nitrogen or argon purged environment. Nitrogen/argon will provide less than 1 percent relative humidity, at atmosphere or a slight negative pressure.
• The HCG can accommodate the same requirements as the Class III BSC but with a purged environment that can provide less than 2 to 3 percent oxygen which can be very instrumental in controlling some bacterium.
• Less turbulent than the BSC III and so finite weighing activities can be done. HCG have a cross flow vs. a downward/upward air flow in BSC cabinets.
• HCGs can be rated hazardous area with a Class 1, Div 1, groups C & D, F & G.
• UV lighting can be used for decontamination.
• Passivation of the main chamber, which provides better cleaning attributes to the surfaces of the HCG.

The commonality of HCG and Class III BSC systems are important to identify as these key features need to be included for both types of systems:

1. HEPA Filtration. In and out.
2. Airlock or dunk tank prior to the main chamber.
3. Gloveports and gloves.
4. Laminar flow is not used in Class III BSCs or HCGs.
5. Exhaust in dedicated and not into the room.
6. Cleaning.

Containment Device  Direction of Airflow (lfpm) Application/Airflow Pattern Protection Appropriate for Some Uses of Volatile Toxic Chemicals and Radionuclides Laminar Flow Clean Bench Outward (100) Any application where the product is not hazardous, but must be kept contaminant free. A laminar flow clean bench provides HEPA filtered supply to the work surface and a particulate-free work area. Examples of processes that are appropriately performed in this type of cabinet include: preparation of nonhazardous intravenous mixtures and media; particulate-free assembly of sterile equipment and electronic devices; polymerase chain reaction (PCR). (Figures 8, 9) Product only Not acceptable BSC Class I Inward (≥75) In at front, exhaust through HEPA to the outside or into the room through HEPA. (Figure 1) Personnel and Environment Acceptable if hard ducted BSC Class II, Type A1 Inward (75) Laminar flow device; 70% of airflow is recirculated to the cabinet work area through HEPA; 30% balance can be exhausted through HEPA back into the room or to outside through a canopy unit. Plenum is under positive pressure. (Figure 2) Product, Personnel, and Environment Minute amounts only if thimble connected to exhaust* BSC Class II, Type A2 (pre-2002 was A/B3) Inward (100) Similar to Class II, A1, but has 100 lfpm face velocity and plenums are under negative pressure to room; exhaust air can be ducted to outside through a canopy unit. (Figures 3, 4) Product, Personnel, and Environment Minute amounts only if thimble connected to exhaust* BSC Class II, Type B1 Inward (100) Laminar flow device; 30-40% of airflow is recirculated and the 60-70% balanced is exhausted through a HEPA filter and a dedicated duct to the outside. (Figure 5) Product, Personnel, and Environment Limited amounts* BSC Class II, Type B2 Inward (100) Laminar flow device with dedicated HEPA filtered supply to the work surface and total exhaust to the outside through a HEPA filter and the building exhaust system. No recirculation, exhaust must be hard ducted to the outside. (Figure 6) Product, Personnel, and Environment Acceptable BSC Class III Inward Totally enclosed, gas-tight, glove ports for manipulation of pathogens. Supply air is HEPA filtered. Exhaust air passes through two HEPA filters in series and is exhausted to the outside via a hard connection. Airflow can be turbulent inside the cabinet (e.g. pharmaceutical manufacturing of potent compounds, BSL-4 agents). (Figure 7) Maximum Product, Personnel, and Environment Limited amounts* * In no circumstances should the chemical concentration approach the lower explosion limits of the compound. (2,1)

When evaluating the process for biohazardous contaminants, the following principles and methods need to be applied:

1. Risk assessment:
a. Recognize hazards and identification.
b. Exposure potentials.
c. Frequency of occurrence.
d. Evaluation of work tasks and equipment
required.
e. Assigning protective measures to specific tasks.

2. Biological contamination evaluation:
a. Risks for workers.
b. Reduction of exposure potentials by evaluating the infectivity and transmissibility.

3. Concentration and enclosure:
a. Confinement of the biohazard
b. Use of one system. Less risk than if work is done in two or more systems.

4. Exposure minimization:
a. Fully enclosed system.
b. Automated features, such as conveyers, specialized equipment.
c. Barrier system between the operator and biohazardous compounds.

5. Physical containment:
a. Barrier for all aspects of the process.
b. Prevention of any aerosol or droplet generation.
c. Interlocks.
d. Robotics or automation of the process.

6. Hazard minimization, activities if an exposure occurs:
a. Safety and contingency plan.
b. Emergency procedures and training.
c. Vaccination, if applicable.

Design is the key to the safety and operational features of any device used for environmental conditions or control. When looking at the initial design, it is key to establish the process flow and operating sequences. What are we going to handle? What mechanics are required to handle the materials of containers?

These items come into play and should be incorporated into a full scale mock up to be assessed by the operators prior to final fabrication. Testing of any automation requirements should be completed and proven. These type of facsimiles will prove concepts and workability of such systems.

System testing

Once you have decided on the best system and design, testing needs to completed. Testing methods are standard and can be applied to the HCGs. Testing of the HCGs would conform to the industry standard and include the following:

Air quality/flow and microbiologic testing.
1. Testing should only be done by a third party.
2. Testing needs to be relevant to the biohazardous substance.
3. Testing of the HEPA filters by DOP with particle analysis a ROYCO counter.
4. Tests using a micro nebulizer.
5. Bacterial or BI are placed in the glovebox and a decontamination cycle is run and submitted for results.
6. Air changes per hour need to be verified.

Containment/ cleaning validation:
1. Third party containment testing can be completed using the ISPE Guidelines.
2. Riboflavin testing for verification of CIP (clean in place systems).
3. Drainability.

Testing should be robust and conform to industry standards for both types of systems.

Summary

The HCG can be used for any biohazardous application with the added benefit of better control, a more robust design, and (typically) a lower cost.

The processes can utilize automation, which in turn provides the optimum in operator safety and concise process manipulations while under a stringently controlled environment. The process can be completed in one system, thus saving floor space and generating less utility requirements — all while reducing risk of contamination.

---

Michelle Frisch is Senior Manager, Global Technical Systems with Powder Systems Ltd., based in Liverpool, U.K. She can be reached at [email protected]. www.powdersystems.com

This article appeared in the November/December 2015 issue of Controlled Environments.