Vented Balance and Fume Hood Array


Finding a product capable of containing a process where powdered product is converted into an aqueous solution can be tricky. Especially if such processes evolve toxic vapors and gases. In these scenarios, weighing with an analytical balance is typically followed by adding the powder to a stirred liquid. At this point, vapors and gases may evolve.

In this case study, Flow Sciences worked with a customer to develop a two-section containment system that optimized containment while maximizing process efficiency. Such designs become even more essential when high potency active pharmaceutical ingredients are involved.

The device depicted in Figure 1 is an example of the custom product FSI produced for such an application.


Our customer had a limited space to perform stirring, weighing, and calibrated solid-liquid mixing operations. Flow Sciences was made aware of chemicals and quantities used in this process.


Flow Sciences proposed joining an open-face powder enclosure with a bag-in bag-out filter and fan (thimble connection to building exhaust) with a polypropylene vertical sash fume hood exhausted to the building exterior.

This arrangement became more defined with multiple phone calls and emails until all parties agreed to the process array depicted below:

Key materials of construction were stainless steel, polypropylene, and anodized aluminum. A deep stainless work space in the fume hood section had hinged doors for final product access and removal.

Successful ASHRAE 110-2016 testing (4 Different Sash positions) completed prior to Product Shipment:


Flow Sciences worked with our customer and devised a unit containing both a HEPA-filtered weighing enclosure and a polypropylene fume hood. A sliding connecting pass-through was also constructed. The weighing enclosure contained the weighing process with HEPA filtration and the fume hood contained the stir plate solvent addition operation. This construction permitted containment of both liquid and powdered substances in two different processes. Process flow was maximized with this design scheme. The weighed powder could be moved from the HEPA balance section to the fume hood through the sliding door, where solvent mixing took place.

All this was done with demonstrated containment in our test room using ANSI / ASHRAE 110-2016.

For More Information – Contact Us

  • What is being done inside of the enclosure? What type of material (powder, liquid, gas, nuisance odor) is being worked with? How does the material enter and exit the enclosure system? etc...
  • What type of filtration is required? Single HEPA, Dual HEPA, Carbon, House Exhaust, etc... What is the required OEL (Occupational Exposure Limit) for the process, or any other details about containment goals? What is the quantity of powder or liquid, task duration, composition of powder, etc...?
  • What equipment is being worked with? What is the equipment model, size, scope, function, and any other information that will affect the design of the enclosure, including movement, heat output, etc...? *State the specific equipment make and model if available*
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    • Are there any additional notes or information that should be considered? Are there any special design requirements?