Combination air purification and ventilation offers a solution for indoor sports and fitness centers in Corona time and beyond!
TU/e (Eindhoven University of Technology) presents research results on aerosol reduction in a fitness room
Participants on fitness machines and on the treadmill
TU EINDHOVEN
Meeting the ventilation standards of the Dutch government is no guarantee that the air in buildings is sufficiently free of aerosol particles (the means of transport for viruses). Even in buildings that comply with the Building Decree, the concentration of aerosol particles can increase considerably during intensive use, such as during sports. This is the main conclusion of experiments conducted by Eindhoven University of Technology (TU/e) in a fitness room of the Student Sports Center Eindhoven. Lead researcher Bert Blocken concludes that a combination of the existing ventilation and innovative air purification can be a good precaution for safe and responsible sports, even during the corona pandemic. The research has been published in the scientific journal Building and Environment.
Although the precise role of aerosols in the spread of COVID-19 is still the subject of scientific discussion (especially in the Netherlands, abroad people are already much more aware of the risk of aerosols), it is clear that clean air and therefore good ventilation is an important precaution that can help contain the corona pandemic. Clean air is especially important in indoor sports facilities, where people sometimes breathe in and out a lot and forcefully.
Participants on fitness machines and on the treadmill
TU EINDHOVEN
This clean air or air quality is closely related to the concentration of aerosol particles, the small saliva droplets that remain suspended in the air. Research by TU/e, among others, now shows that ventilation alone is usually not sufficient. To keep the concentration of aerosol particles in indoor sports facilities constantly low, additional air purification is necessary.
Cleaning that uses good filters in combination with UV-C light appears to be very effective: together with the ventilation system, they remove 80 to 90 percent of the aerosols from the air. Follow-up research will have to show whether this combination of air purification and ventilation also shows the same results with other technologies and in other environments, such as nursing homes, schools, indoor (sports) stadiums, offices, restaurants, theaters, elevators, etc.
Aerosols
It is well known that people can transmit the coronavirus through larger droplets of fluid from the nose or mouth. The 1.5 meter rule is based on this: the drops are so heavy that they usually fall to the ground within that distance and no longer pose a threat. There is still no unequivocal position among scientists that the smaller saliva droplets, the so-called aerosol particles, also play a role in the spread of this virus.
These aerosol particles are so small (less than a few tens of micrometers) that they linger in the air and can even accumulate, especially in enclosed spaces, such as a gym, where people gather and exercise intensively. Ventilation is therefore of great importance for air quality and for limiting the possible risk of contamination. RIVM therefore advises owners of gyms and other sports accommodations to ventilate well.
Professor Bert Blocken of TU/e and KU Leuven, one of the researchers and expert in the field of air flows, calls this the precautionary principle: even though we are not yet sure whether and to what extent high concentrations of aerosol particles lead to transfer of the coronavirus, just to be sure we better avoid them. Since the introduction of the current Corona protocol, there are no known sources of COVID-19 infection within Dutch gyms. "That is the case in the United States," says Blocken. "There, researchers identified an outbreak at a Chicago gym, presumably through aerosols."
Experiment
To see how this works in practice, Blocken and his colleagues did a number of experiments at the initiative of Sportinnovator in a fitness room of the Student Sports Center Eindhoven. After first building simulation models and a series of experiments with artificially generated aerosols, 35 test subjects came together there for intensive sports.
A participant in the TU / e research
TU EINDHOVEN
The solution for all gyms
Healthy-Office.nl
The setup in the TU / e student sports complex
TU EINDHOVEN
Using almost 150 sensors, the researchers kept track of exactly how many saliva droplets ended up in the air, and how ventilation can contribute to keeping the air clean and healthy. It was then examined whether air purification could offer a solution. The researchers used two cleaning units for this.
The units suck the air in from the bottom and blow filtered air out from the top at a height of 1.6 meters. For example, the air was filtered at walking height. And they did it very efficiently: together, the purifiers (with a total capacity of 1234 m³ per hour) were about as effective as the ventilation system with a capacity 1.5 times higher. In just one filter cycle, they were able to remove 98-98.5 percent of all aerosols from the purified air.
The tested purifiers have another major advantage: because no air has to be supplied from outside, it does not have to be heated either. They are therefore very energy efficient: the two units together consume 210 W. Several other air purification technologies are currently being investigated for similar results.
Optimistic
Not only scientifically, but also cost-wise. Making an existing mechanically balanced ventilation system in a gym ten times stronger will easily cost 40,000 euros. This solution is up to a factor of ten cheaper and more energy efficient. And with enough air purifiers you may even be able to get close to the air quality as it is outside." These air purifiers will always have to be used in combination with existing ventilation. "They do not remove CO2 from the air.
"The cleaners are efficient, they make an expensive upgrade of existing ventilation systems superfluous, and they can be used flexibly. In addition, they offer a solution if we are less able to ventilate because of the cold by opening windows and doors." Blocken calls this good news for all indoor sports facilities and especially the gyms, but also for public health. "It is especially important during a pandemic that people stay fit and healthy."
The filters could possibly also be used in other areas where aerosols can accumulate. Whether they are just as effective there remains to be seen in further research. Blocken and his colleagues are currently conducting follow-up research in the Johan Cruijff ArenA in Amsterdam, the Maaspoort in Den Bosch and the top sports locations CTO Papendal and CTO The Hague. They will also perform additional computer simulations (so-called CFD simulations) to gain more insight into aerosol behaviour, ventilation and air purification.
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