Although the regulations imposed earlier during the peak-COVID season have been eased of late, COVID-19 related problems have not yet gone – instead of that they are coming back with more vigour and causing new types of ailments. The symptoms of attacks of the CORONA variants have also changed.
With this backdrop, the entire world is now realising the role of ventilation as one of the most important factors to keep away the chance of CORONA-related and other infections.
A recent Italian study (Source: Reuters, Dt. 22.03.2022)
An experiment overseen by the Hume foundation think-tank compared coronavirus contagion in 10,441 classrooms in Italy’s central Marche region. COVID infections were steeply lower in the 316 classrooms that had mechanical ventilation systems, with the reduction in cases more marked according to the strength of the systems.
With applications guaranteeing a complete replacement of the air in a classroom 2.4 times in an hour, infections were reduced by 40%. They were lowered by 66.8% with four air replacements per hour and by 82.5% with six air replacements, the study showed.
Most of Italy’s schools lack mechanical ventilation systems. Instead, teachers are urged to keep windows open when weather conditions permit.
If the most efficient systems were installed “we could pass from 250 cases per 100,000 students (the alert level set by the education ministry) to a rate of 50 per 100,000,” the Hume foundation and the Marche regional government said in its press release.
The experiment was carried out between September 2021 and January this year (2022). Italy saw a rapid acceleration in COVID cases in December and early January, before a decline from mid-January until a couple of weeks ago (around March 08, 2022). They are now rising again, driven by a new strain of the Omicron variant, though new hospitalisations and deaths continue to decline.
The country has registered 157,904 deaths linked to COVID-19 since its outbreak emerged in February 2020, the second highest toll in Europe after Britain and the eighth highest in the world. It has reported 13.89 million cases to date. On Monday (March 21, 2022), the (Italian) health ministry reported 32,573 new cases, against 60,415 the day before, while the number of deaths rose to 119 from 93.
What does it tell us?
Lack of proper ventilation is one of the main reasons behind spread of CORONA-related infections. In any thickly populated country like India, avoiding crowded public transports is practically next to impossible. However, we are not safe even within the closed environment. As in most of the rooms or homes, we do not care for air replacement, the same air circulates inside the room and inhaled by the occupants on a recurring basis for hours. Thus, it goes without saying that we need to be very careful.
What do we need to understand?
Because of global warming, average middle-class people are nowadays installing air conditioners at their residences, however, most of them are not aware of the fact that an ordinary air conditioner cannot purify air. It’s not a device to maintain IAQ (Indoor Air Quality). The scene is ubiquitous that all the windows are closed and the AC unit is on throughout the day to avoid heat.
The common AC unit installed at a home or a room just sucks air from inside the room, cools it and throws back the cool air inside the room. So, it is just a device to lower the temperature of the air enclosed inside the room.
When you see a big metal box fixed on the balcony or terrace or on the wall outside a room or home, you may think it’s sucking fresh air from outside, but that’s not at all true. The box is just discharging the collected heat from the inside air to the outside air.
What do we need to care for?
We have to ensure that the air changes inside our room or home is complying with the standard. ANSI/ASHRAE Standards 62.1 and 62.2 are the recognized standards for ventilation system design and acceptable Indoor Air Quality (IAQ). Expanded and revised for 2019, both standards specify minimum ventilation rates and other measures in order to minimize adverse health effects for occupants.
As per ASHRAE 62.1, residential rooms or homes should receive at least 0.35 air changes per hour per occupant under normal condition. The table above shows the air changes recommended by ASHRAE for different enclosed areas for single occupancy. If the occupancy increases by ‘n’ times, the required air changes per hour will also increase by ‘n’ times.
However, ASHRAE guideline specifically mentions, when dealing with viruses such as COVID-19 or other airborne infections, it is recommended to have a higher ventilation rate, in the proximity of 6-12 air changes per hour.
Importance of cross ventilation
As per United States Environment Protection Agency (EPA), indoor air can be 2 to 5 times more polluted than outdoor air; therefore, most HVAC system designers understand that increased amounts of outdoor air supply is generally better for IAQ.
In most of the parts of India, we do not have the problem of excessive moisture, thus we generally need not worry for moisture control. So, having more windows and keeping them open is a good practice.
EPA also states: Strategies using natural ventilation include wind driven cross-ventilation and stack ventilation that employs the difference in air densities to provide air movement across a space. Both types of natural ventilation require careful engineering to ensure convective flows. The proper sizing and placement of openings is critical and the flow of air from entry to exit must not be obstructed (e.g., by closed perimeter rooms).
Exhaust fans are very essential
Whether it is in residential or public environment, strategic installation of exhaust fans is very important. An exhaust fan throws the bad or used or contaminated air out and helps in sucking the fresh air inside.
In India, we find that some homes have exhaust fans in kitchens and wash rooms. Unfortunately, the doors of wash rooms are often kept closed. It completely nullifies the purpose of throwing out the indoor air. To save energy cost, the kitchen exhaust fans too are often kept off during non-cooking hours.
It is always better to let the exhaust fan work around the clock, especially in homes or apartments that do not enjoy the benefit of natural drift of air through cross ventilation. These devices not only discharge the odours and excess moisture but also throw out the contaminated or germ carrying inside air.
In any room or home, that has no air conditioning device, strategic use of exhaust fans can lower the indoor temperature slightly. As, during winter season or sometimes in rainy season, all the widows are kept closed in many Indian homes, strategic use of exhaust fans is very essential. It will not only keep the room reasonably dry but also help in maintaining a reasonably good IAQ. Thus, like air conditioners, exhaust fans also must be treated as home or room comfort devices.
Finally a few important words
We are perhaps again going to face a tough situation as different variants of COVID-19 have started spreading again. As we have already experienced, we may have to again lock in ourselves inside our residences. Thus, creating provision for maintaining the best IAQ is very essential at this juncture.
Nowadays, there are many devices available in the market for maintaining the IAQ, however, they also need proper maintenance, and most of them are costly enough for middle-class people. Thus, I have talked about a simple provision for maintaining a reasonably good IAQ, to mitigate the chance of catching diseases because of poor IAQ. Definitely, use of IAQ enhancing devices add value to the process.