Mining Project: Point-of-use Ventilation Systems to Prevent Exposure to Airborne Viruses
To develop and test ventilation systems in combination with HEPA filters to document their effectiveness for protection against airborne virus particles.
There are major reports in the U.S. news about long-term care facility residents and workers, meat/poultry processing workers, and cashiers in grocery/retail stores contracting the COVID-19 virus. Some of these cases have resulted in deaths. Long-term care facilities account for over one-third of COVID-19 deaths. In these facilities, sources of exposure include infected health care personnel and residents. While hospitals have airborne infection isolation rooms, long-term care facilities do not. For workers in meat/poultry processing plants, the source of exposure is infected workers, which can be from exposure to droplets in the air or from contact with contaminated surfaces. The number of affected people is sufficiently large that several meat processing plants have had to shut down. Cashiers in various industries are exposed to viruses by interacting with COVID-19-infected customers or by touching COVID-19-contaminated items/surfaces and then touching their eyes, nose, or mouth. As a result, high numbers of grocery store workers have also been infected.
These groups have similarities in the way they are exposed to COVID-19, with airborne exposure and contact with contaminated surfaces being the main sources of exposure. One potential way of protecting these groups is to provide clean air around them or extract the contaminated air using a hood in their work area. This hood could be used in conjunction with barriers. For some workers, it may be beneficial to use a canopy to blow air over the worker, providing clean uncontaminated air to their breathing zone. In these cases, the idea is to protect the worker from contaminated air by providing a constant stream of air flowing over the worker from above.
This pilot project will test three types of point-of-use ventilation systems: a push (blowing plenum) system, a pull (exhausting hood) system, and a push-pull (a combination of exhausting and blowing hoods) system. The systems will be tested in combination with HEPA filters to document their effectiveness for protection against particles ranging from nanometers to microns in size. The approach taken is referred to as point-of-use, meaning that ventilation provided by the system at the worker location rather than relying solely on a building’s HVAC system.
In this project, the work will be undertaken by way of three research aims, as follows:
- Evaluate a push system to protect a worker from being contaminated by airborne virus particles. NIOSH has extensive experience in developing engineering controls to provide clean air for workers in underground mines. NIOSH successfully developed a canopy air curtain (CAC), which is a push system, for protecting miners from respirable dust and diesel exposure and is currently working with a company to modify the original NIOSH CAC design for use in mitigating airborne coronavirus exposure for cashiers. The new system is more compact, uses a HEPA filter, and incorporates a better seal design between the filter and the filter mounting surface to capture nanometer particles in the range of the coronavirus. This coronavirus CAC could be attached to the ceiling with cables or mounted on a portable stand so that it can be positioned right above a worker.
- Evaluate a pull system to protect a worker from being contaminated by airborne virus particles from other workers. For meat/poultry processors, pulling the air up over them using an exhausting hood could be a better method, since blowing air downward could contaminate the working surfaces and meat. Because the goal is to protect the workers from each other, the exhausting ventilation hood would be close to the workers’ breathing zones to extract virus-contaminated air from above an infected worker so that it does not spread to other workers. The process would be to place the exhausting hood over the worker, extract the air around the worker, and capture the viral aerosols with a HEPA filter. This could be combined with UV light and heat to kill the virus. In addition, a UV light could be located in the vicinity of the belt and meat to kill the virus on working surfaces.
- Evaluate a push/pull system to reduce airborne virus particles for workers. A pull ventilation system provides less airflow than a push ventilation system with the same air velocity. One way to improve this is to use a push-pull system, where air is blown in the direction of the hood to help push the air towards the hood. In the meat/poultry processing case, a blower could provide airflow beneath the worker (the air would first pass through a HEPA filter to capture any bacteria, virus, and contaminants) and push the air up to a pull system, which would draw contaminated air away from the workers and surfaces.
The anticipated outcomes of this project are journal articles detailing the results for each type of ventilation system, which will be tested in both laboratory and field settings. Researchers will also monitor field installations to determine the impact in relation to COVID-19 cases reported at facilities using this technology. The ultimate goal is to provide research outcomes that will inform new or update existing COVID-19 response guidance documents and help workers to perform their duties safely.
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