NEWS RELEASE May 2020
Laminar Flow Not Partitions and Masks Not 6 ft Distance are the New Recommendations
Meat processors, and many other entities trying to mitigate COVID-19 are moving forward based on guidelines which have been made not only obsolete but dangerous.
Meat processors have received guidance from the CDC to install partitions and to wear some type of cloth mask. Based on the latest evidence this is not good advice.
Fifty years of cleanroom design has resulted in consensus that HEPA filtration and laminar downward air flow are the ways to deal with particles smaller than 5 microns. Air pollution control experts can cite endless examples of small particles which travel around the globe. No amount of partitioning would restrict them.
Technology has been developed to deal with COVID-19 in a safe and cost effective manner by cleaning the air and directing the flow so it is not from person to person. The 6 ft voting line in Milwaukee is a good example of what not to do. A slow sequence of people moving in a straight line creates a lineal viral cloud and so people in the rear are continually walking into the cloud generated by their predecessors. In Milwaukee seven COVID case were directly tied to the voting and the entire Wisconsin caseload rose noticeably.
One takeaway is that air flow direction is very important. If a cloud moves from one meat packer under or around a partition to another worker, the partition has no positive effect and in fact may create turbulence and longer suspension. In the diagram below envision each worker in a cavity area caused by the partition where the virus keeps circulating.
There are ceiling mounted fan Filter Units (FFUs) which will provide laminar flow of HEPA filtered air. If placed properly they can provide laminar flow of clean air downward.
Meat processors are only one of the many applications where fan filter units and not partitions should be used.
The aisles of stores can also be supplied with laminar air flow ceiling mounted FFFUs.
In terms of what is needed cigarette smoke can be used to illustrate the effectiveness of a design. In the laminar flow systems it will be removed. It would easily circumvent partitions.
The guidance to meat processing workers to wear a cloth mask but not an N95 mask because there will not be enough for healthcare workers is also obsolete advice. The production of N95 masks has increased by orders of magnitude in recent months. The shortage of meltblown media is being met in several ways including rapid construction of new media lines and development of nanofiber membranes as a washable alternative. Various decontamination methods for masks are now available.
Everyone should be wearing an N95 efficiency mask. The new evidence of transmission by small aerosols including Italian research which found coronavirus on air pollution particles in the Lombardy region means that what is needed is to remove particles smaller than 3 microns with high efficiency on 0.3 microns and even 0.1 microns.
The N95 mask is actually tested with 0.l micron aerosols and achieves 95% efficiency on these particles. Single use face masks do not even remove all the 3 micron droplets. Surgical masks have only 30% capture rate on 0.1 micron particles. It is true that viruses are generally found in droplets or on particulate which is larger than 0.1 microns but the fact that viruses are traveling long distances testifies to the small carrier size.
Another challenge is leakage around the mask, N95 masks are designed for minimum leakage. Surgical masks are loose fitting with considerable leakage. N95 masks can be supplied with or without valves. There is lower leakage and greater comfort if a valve is provided. On the other hand the valve allows unfiltered breath discharge. Both designs will have their place.
The conclusion is that HEPA filtered laminar air environments and high efficiency masks will provide a relatively safe working or shopping environment. Partitions and 6 foot distancing with cloth masks are not nearly as protective.