Experts warn that this week's return to school could lead to an increase in Covid cases. We examine measures that could improve the air quality at schools and decrease transmission.
Carbon dioxide (CO 2 ) monitors
Poor ventilation and crowded rooms can lead to higher levels of CO2 in the air we breathe. While CO 2 monitors don't alter air quality, they are an inexpensive, efficient canary in the coal mine.
Experts have pointed out their limitations in areas with low occupancy or large volumes.
Sage member Catherine Noakes from the University of Leeds spoke in her personal capacity to say that classrooms are a great place for CO2 monitors. She said that their spaces are just right in size and have regular occupancy.
Opening windows
Many schools will only have opening windows [for ventilation], but Dr Shaun Fitzgerald, an expert on ventilation at the University of Cambridge, stated that many school classrooms will have these types of windows.
Noakes stated that schools should make sure windows are open in the short-term.
It is possible to quickly make a room very cold by opening all of the windows. However, the amount that they should be opened to increase ventilation will depend on the wind speed and temperature difference between indoors and outdoors.
Sage's Environmental Modelling Group (EMG), has reported that in colder temperatures, a slight opening of the window can provide ventilation that is nearly as efficient as fully opening it in summer.
Noakes tweeted a variety of tips for improving ventilation through opening windows. She suggested that high-level windows are a good option for winter ventilation. The cold air will be able to mix with the warmer air and not cause a cold draft in your space.
Fitzgerald stated that heat exchangers and fans may be required to mix warm air with cold air if high-level windows are not present. Noakes stated that many CO2 monitors can also measure temperature. This can help teachers determine if they are able to close the windows when CO2 is low or your temperature is low.
Ozone disinfecting machines
Ozone has been shown to be effective in killing coronaviruses, according to some studies. However, it can also cause irritation and damage to the airways. People must be taught how to safely use the machines.
Noakes said that ozone disinfection cannot be used in occupied spaces. He also stated that it can take up to five hours.
You would probably only do it if you have an outbreak. She said that you wouldn't do it every day and that the benefits may be limited because the virus can disappear overnight even in poorly ventilated rooms.
I'm not convinced they can replace regular cleaning, Noakes said, echoing concerns raised by the Health and Safety Executive.
Air conditioning
Noakes said that mechanical ventilation units are beneficial because they allow for fresh air to enter the system. But, recirculating air can make matters worse.
People believe they are comfortable so they think their rooms are well ventilated.
Air cleaners
Although there are many products that purport to clean the air, Noakes stated that evidence is not conclusive. An ultraviolet cleaning device is one option, though they can be difficult to install and design.
An air filter is another option. It is basically a box with a fan and fine HEPA filters. The device draws air through it, and any viruses or other contaminants are eliminated.
They can be loud so it is important that you choose the right size.
Noakes stated that you probably need at most two for each classroom. He also said it is better to identify areas where ventilation may need improvement, but windows can't be opened.
