This blog is not intended as advice. It is for educational and research purposes only. Read this disclaimer first if you want to read this post.
The use of protective sneeze screens in shops is interesting because it may actually increase the COVID-19 risk.
A few years ago I researched the use of sneeze screens for a customer-orientated government client based at International Airports I found that the use of sneeze screens was not evidence based. There was no research demonstrating they worked, but there are a lot of suppliers.
When I used theatrical smoke to demonstrate air flows, the smoke went around the screens and swirled into the face of the person behind the screen. It could actually make things worse, as people tend to raise their voice and lean forward when confronted with a screen.
Every surgeon knows that it is best to keep voices low in an operating theater to reduce the spread of contaminated aerosols. You should not speak unless spoken to by the surgeon and a reply is expected.
For the Woolworths screens, it is likely that the air flowing under and over the screens would curl towards their employees faces. The COVID-19 virus appear to attach to receptors deep in the lung. Only droplets around 5 microns (5/1000 mm) can penetrate that deep into the lungs. It’s the physics on inhalation toxicology. At this size, these invisible droplets are not going to splatter on the screen – they will just drift in a cloud and the screen can make things worse.
The whole idea of sneeze screens may be reasonable for protecting food (but again I could not find research to back their use). When you sneeze, the head initially tilts back and during the actual sneeze, the face points downwards. A food sneeze screen would intercept some of the larger sneeze droplets. However there is no evidence that sneeze screens for people give any protection and it appears that Woolworths has translated their use with food to protecting people.
To get any protection to workers, it is probably better to concentrate on air flows so there is no airflow from the customer to the employee. The best situation would be to have downdraft ventilation with the employee standing on the exhaust grill and the clean air supplied from above.
Unfortunately, most air conditioned air in commercial buildings is largely recycled and being in a shop is a bit like being on a cruise ship. Sounds scary, doesn’t it? Making the air conditioned air only fresh air means a single pass and tripling of the air conditioning costs – if the system is built to do this. Slightly increasing the air temperature and moving to single pass air conditioning may help.
Possibly the best approach is building a low shelf in front of the operator – low enough to be below the center of gravity of the customer and somewhere they can place their shopping would probably be more protective than the screen. People will not lean forward over a low shelf as they feel they may topple. It would ensure Social Distancing between the customer and employee – and would likely be cheaper and better. You now see this arrangement at international airports.
