Can We Hear More from Engineers?
Inviting More Public Dialogue on COVID-19 Engineering Mitigation Measures
Quinn Skinner
As many have predicted, the food supply chain is now being affected. My wife recently reported that the local high-volume discount supermarket is limiting meat purchases, just three days after the President ordered that meat processing plants shall not be closed. It does not appear, at least to the public eye, that protection for these workers has received the same rigor of analysis and action as others deemed “essential.” Recently, the CDC and OSHA put out joint “interim guidance” that provides the recommendations one might expect: spacing out people on production lines, staggered shifts, PPE, employee screening, and sick leave, etc. However, these measures do not address the significant risk posed by sharing the recirculated air used at most facilities. While there may be corporate discussions along these lines, i.e., relying on windows rather than air conditioning, new ideas and discussion of “best practices” do not appear to have much public attention. I seek to elevate this discussion with a conceptual proposal that uses a combination of inexpensive, existing technology and installed equipment to bring in fresh air, which is subsequently pulled up and away from workers so that it recirculates less among them.
Concept
The “exhaust-driven misting cyclone virus mitigation system” (Figure 1) pulls workers’ exhaled breath up and away from them. Something then has to be done with the viruses in small droplets or aerosol form carried in this exhaust. Otherwise, merely pumping this air outside provides opportunity for recirculation back through the windows or the surrounding community. So, the proposal includes passing the exhaust air through a mist to capture these droplets, then pushing the misty exhaust through a transparent cyclonic separator. The separator, little more than a spiral path for the air, causes the air to spin — and centrifugal force carries the droplets to the side of the container, from which they drain into a pipe to the sewer. The separator is transparent and outdoors to capitalize on UV rays from the sun killing some viruses, augmented by UV lights (like those in a tanning salon).
Referring to the numeric labels on Figure 1:
(1) Windows are kept open everywhere to admit fresh air.
(1a) (Some facilities’ internal areas require special temperatures, e.g., <50˚F for meat processing areas, so some sort of supplemental air conditioning or other mitigation measure may have to be applied.)
(2) Overhead ventilation is rewired to exhaust only.
(3) Air removed from workspaces passes through a heavy mist to capture as many viruses as possible that may be floating in droplets or aerosols.
(4) A transparent cyclonic separator removes the moisture; the sun and UV lights kill many of the viruses.
(5) Moisture removed drains to the sewer.
These cyclonic separators could be anything made of transparent plastic that spins the air and/or forces it through sharp turns. They need not have moving parts; I don’t think it will matter much whether they are cylindrical or square. They may need custom sizing (diameter / width) so that they impart enough velocity to the exhaust air (like a nozzle) to affect the moisture separation. UV lights are easily obtained.
Caveats and challenge
I offer the above as a concept, not a design. I recognize that rewiring ventilation to exhaust will be easier said than done in many cases. Other restrictions such as filters, reheaters, etc. will also have to be modified, bypassed, or removed to accommodate reverse flow. And I have waved my hand very broadly over special concerns like temperature control for specialized operations.
Those more experienced with design are welcome to shoot a thousand holes in this, but I challenge them to recommend alternative solutions that are inexpensive and executable in the short-term — weeks, not months or years. If this effort is already well underway, I hope this brief proposal brings more worthy candidates to the public’s view for their reassurance. While evidence grows that many “lockdown” measures have been overkill, those workers compelled to work in tight spaces with recirculated air have substantial cause for concern. Before we nationalize any more “essential” industries and effectively make their employees subjects of the state, we should expend some engineering capital on their behalf.
Quinn Skinner is a retired naval officer with a B.S. in mechanical engineering and experience managing ventilation, refrigeration, and air conditioning systems on Navy ships.
