What is an AEC Downflow Booth?

Where and when are AEC Downflow Booths used?

Can I use both solvents and powders in a re-circulatory Downflow Booth?

Does the AEC Downflow Booth provide any competitive design advantages over the competition?

What containment performance is possible from a Downflow Booth?

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What is an AEC Downflow Booth?

The Downflow Booth is an engineering control that achieves containment by air entrainment. A Downflow Booth achieves containment by providing unidirectional HEPA filtered airflow, typically 90-100 feet per minute when measured three inches from the ceiling diffusers over the safe working zone. When the Downflow Booth is used as designed, this downward flow of unidirectional air entrains dust particulate released from the process, away from the operator. The particulate entrained in this downward flow of air is then recaptured by a low level exhaust and passed through prefilters and HEPA filters to substantially remove the particulate. Typically this air is then re-circulated to the supply plenum resulting in a ‘push/pull’ system. Since the booth is an ‘open front’ design to allow easy access of materials and personnel, there is always a ‘bleed in’ of air that can potentially result in a positive pressurization of the system. To eliminate this situation, Downflow Booths are fitted with features to allow a ‘bleed out’ of air after the HEPA filter (positive pressure side of system) to maintain the design balance. This ‘bleed out’ of air, dependent on the application, is either re-filtered or released without further filtration. Due to the open nature of the Downflow Booths, they are very versatile and allow for a wide range of processes to be performed within them.

Where and when are AEC Downflow Booths used?

Whenever there is open handling of highly hazardous powders. Most commonly used in the Pharmaceutical, Cosmetic, Fine Chemical and Nanotechnology Industries. 

Can I use both solvents and powders in a re-circulatory Downflow Booth?

It is not advisable to re-circulate the air when solvents are exposed to the airstream. The Downflow Booth can be outfitted with carbon filtration, however this is primarily to control odors from fragrances, etc.

Does the AEC Downflow Booth provide any competitive design advantages over the competition?

The AEC Downflow Booth design holds several key advantages over the competition:

• Superior supply airflow distribution: AEC utilizes independent ceiling diffusers vs. one common pressurized plenum. Benefits of this terminal system include:
  • Control of airflow volume to each terminal diffuser through the use of individual dampers integrated into the diffuser. This assures that the individual diffusers receive an equal flow rate, vs. one common pressurized plenum that allows for unequal distribution.
     
  • The 304 SS face of the diffuser helps protect it from foreign objects (such as a vacuum wand). In event of damage or contamination, the individual terminal diffusers are easy to clean or replace compared with one common plenum.
     
  • Gasket seals can be easily wiped clean vs. gel channels in the ceiling plenum that need to be scraped out and re-poured if contaminated with construction or product dust.
• Louvered Exhaust Grills with quick release: These grills are easy to wipe clean and are quickly removed (without hand tools) for cleaning and/or access to the slide-in prefilters. This design is a significant improvement over the perforated holes that are structurally flimsy and very difficult to clean due to the large surface area each hole creates.
• Low Noise Levels: The AEC Downflow Booth is a leader in low noise operation. This is accomplished in part by harmonically tuned fans, radius air turners, and noise insulating panels installed on the rear bulkhead wall.
• 304 SS construction as standard: The booth’s ceiling, walls, ductwork and filter housings are 304 SS construction. 304 SS does not suffer from the concerns of paint flaking and carbon steel rusting that the powder coated alternatives do.
• Highest quality filter housings: AEC uses stainless steel filter housings from Camfil Farr on all of our Downflow Booths. Camfil Farr housings are widely considered to be the industry’s best for durability, features, and construction quality. Other Downflow Booth manufacturers build their own powder coated steel filter housings as a cost saving measure, however the lower quality of these aforementioned housings and their awkward filter tightening mechanisms create long term obstacles for the client’s maintenance group during filter change-outs.
• Domestic Support and Fabrication: AEC booths are manufactured and tested in the U.S.A and we have a full service facility in Groton, CT. We stock filters, spare parts, and maintain all of our own test equipment. Our experienced service group provides a maintenance and inspection program, which may include filter integrity testing, performance testing, etc. to meet your ongoing requirements.
• Guaranteed Containment Performance: The AEC Downflow Booth has undergone performance verification by SafeBridge Consultants, an independent third party, and the results show the Downflow Booth alone demonstrated exposure control at 1µg/m³, using good operating procedures and techniques. Report is available upon request.
• 3D Design and Laser cutting of steel: Our engineers design all of our equipment in 3D CAD, to ensure that every hole matches exactly with every threaded fitting. This design is then fed directly into the laser cutter during the booth fabrication. The consistence and high tolerance of this pairing allows our Downflow Booths to be installed quickly with little or no on-site delays.
• Computational Fluid Dynamics Analysis (CFD): Our engineers can simulate airflow patterns and particle traces by building simulated layout scenarios inside of the Downflow Booths, allowing design changes to be initiated before the booth is built. If a client has an especially large item that will be going inside the booth, such as a large table, conveyor, or piece of process equipment, flow analysis can determine what provisions need to be met to ensure the containment performance of the booth is minimally affected.
• Considerations:
  • Other considerations when permitting safe handling of materials inside the AEC Downflow Booth area include:
  • The operator stays within the safe working zone (SWZ) of the booth.
  • The handling operations take place below the operator’s breathing zone.
  • The operator follows good operating procedures and exercises reasonable care.
  • The air outside the booth is not excessively dirty.

What containment performance is possible from a Downflow Booth?

The AEC Downflow Booth is an appropriate control for materials with a permissible exposure limit (PEL) of <100 µg/m³, reported as an 8 hour TWA. Lacking an established PEL, (or TLV) established by OSHA (or the ACGIH), this same limit would be applied to user derived and prescribed OEL.
The basis of this claim is substantiated by the surrogate testing we did with SafeBridge’s assistance on our standard Downflow Booth. This testing, done with 25 kg hand transfer of lactose, using the ISPE good practices guide, showed an operator’s breathing zone maximum concentration of 1.54 ug/m3 (1.01 mean on three iterations), based on a 37 to 39 minute work duration which included a 10 to 15 minute “rest” period. This value is then more appropriately called an exposure limit by task, or approximately the 30 minute TWA measured during the task.
This concentration would result in an 8hr TWA well below our 100 ug/m3 claim (if exposed to this concentration for 8 hrs, the 8hr TWA would calculate as 1.54 µg/m³). Since work practices and material properties play such a significant role in actual airborne concentration, we would never be comfortable in “guaranteeing” a control down to the 1 ug/m3 range as this testing would imply. We can say, however, that this testing demonstrates that the booth can be reasonably expected to achieve the 100 ug/m3 airborne concentration range for small scale transfer of material (on the order of 25 kg) typically applied to down flow booth technologies.

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