Balkill H has been successfully implemented to sanitize indoor air in an office.

The system has been installed in the offices of an insurance company in Florence where the owners wanted the highest level of of air quality for their staff and clients under the circumstances of Covid19 contagion.

Room size/number of people present

The room is equipped with split air conditioners, the size is 61,77 sq m. (8,39 m. lg, 7,58m. wd, 3m.ht) the volume of the room 191 m3. The number of people working in the room sharing the same air for six hours a day is 6, the number of clients entering/exiting the room is on average 18/20. Everybody wears masks as mandatory by law.

Objective

Sanitize the indoor air of the office in 1 volume per hour, with a following test to prove the abatement of airborne bacteria (as it is not possible to clinically test the presence of covid in unauthorized environments, since the bacteria are more difficult to eliminate, the deduction is that the ratio of bacteria eliminated corresponds at least to the same ratio of potentially dispersed viruses).

Methodology and analysis

4 devices have been fitted in the ceilings, each one 55 m3/h, total of 220 m3/h air flow rate.

On the 3rd of November 2021, at 6 p.m., at the end of a day’s work at the insurance office, without ever opening the windows to change the air, Professor Alberto Cigada of Politecnico University in Milan and his équipe started the air sampling following a protocol. At that time the air was then supposed to be “dirty” with all the natural bacterial load that each person carries.

The protocol was : take the samples of the microbial load in the air in different parts of the room, procedure repeated after 2 hours, after 14 and after 18 hours, using Microbiologic Air Sampler Duo-SAS 360, an instrument that allows the aspiration of a known volume of air (in the specific case 20 liters and 50 liters), which is conveyed onto Petri dishes containing PCA, a suitable substrate for microbiological culture, so as to hold the airborne particles. The PCA plates, once removed, are incubated at 25 ° C for a period of 96 hours to allow the growth of the bacteria and their count.

After the first sampling, the devices were switched on to full power 100%, with two people remaining in the office. The air sampled after 2 hours, when analyzed, showed an efficacy of bacteria abatement of 77%.

With the devices left to operate at 50% power all night long in absence of people, another air sample was taken in the morning at 8 p.m. before the arrival of staff, and after the analysis showed an abatement of 97% of bacteria.

Leaving the devices set at 50% power to keep the noise low, at 12 a.m another sample was taken. This showed a removal of 82%.

Conclusions

The percentage of removal of airborne bacteria just after two hours is impressive, considering the high level of indoor pollution due to the presence of 6 people of staff plus 20 clients remaining 15 minutes each approximately throughout the day.

The removal of airborne bacteria in absence of people was 97% even if the power was set at 50%.

The last sampling at 12 a.m. on the following morning showed that, set at 50% of their power, the devices were able to maintain a high level of removal of bacteria – 82% – even in the presence of people continuously releasing them.

According to a mathematical model developed with the same unit of measurement used in the test, if during the morning hours in the presence of people Balkill had been used at full power, the percentage of abatement of bacteria would have risen to 93.84 %.

Advice

These findings suggest that, if the devices in the office are set at full power during the lunch break, the percentage of removal of bacteria will rise rapidly and clean the environment to the point that a high level of removal of airborne pathogens can be maintained all along the following three hours of work, keeping the air clean and mitigating the risk of contamination.

However, setting the devices to operate at 100% full power in the presence of people is always possible in an emergency to achieve faster sanitation, the only drawback being the noise.

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