Months after the COVID-19 pandemic, there are still many unknowns about the virus, including all the ways it can be contracted. And as the coldest arrives, understandably there is more concern about the ways the new coronavirus may spread indoors.
Although the main mode of infection appears to be close human-to-human contact and exposure to respiratory droplets when a sick person coughs, sneezes, or talks, experts have recently revised their guidelines to include airborne transmission. This means that once the virus reaches the air via respiratory droplets, it can remain there for minutes to hours, potentially infecting others even after the sick person has left the space.
Although airborne transmission does not appear to be a big problem outdoors, where the virus is most likely to spread, confined spaces can increase the chances of infection. This is especially important to consider as colder weather approaches and more people start spending time indoors.
That is why ventilation, the amount of fresh air from outside that flows into an interior space, becomes a vital factor in disease prevention. In fact, the World Health Organization report that poor ventilation indoors can increase the spread of the coronavirus.
Although good ventilation alone is not enough to stop the spread of the virus, it can, in combination with the use of masks, social distancing, proper hand hygiene, and routine surface disinfection, reduce transmission rates.
5 ways to check if a space is well ventilated
Does the space seem congested?
If a place feels unusually stuffy or smelly, it could be an indication of low ventilation rates. But spotting a stuffy room isn't usually that straightforward.
People are terrible ventilation sensors, at least when it comes to indoor air quality. The result is that we cannot necessarily feel that a space is poorly ventilated as we can feel that it is poorly heated.
To make matters worse, many things that could collect in the air are not easy to detect, including viruses, carbon monoxide, formaldehyde, and other dangerous particles.
Since it can be difficult to tell if a room is sufficiently airy, the best thing to do is practice social distancing and wear a mask when you are locked up with other people.
In fact, a September 2020 study, published online in the Journal of Fluid Mechanics, found that face coverings stopped people's impulse to breathe and slowed the spread of droplets, thereby reducing the amount of contaminants recirculated through. of the room by ventilation.
Notice the grimy place?
There is evidence to suggest that keeping relative humidity in the 40 to 60 percent range reduces the risk of infection. This is also in the optimal range of thermal comfort, which means that it is beneficial for everyone.
That said, studies suggest that weather and weather-related humidity can reduce the transmission of COVID-19. However, we do not know what this means for artificially generated indoor humidity.
An August 2020 study published in Physics of Fluid concluded that high humidity can extend the lifespan of medium-sized respiratory droplets in air by up to 23 times. But we must interpret these findings with caution, as the research was conducted in a laboratory setting, which could vary greatly from real-life settings.
Using indoor humidifiers solely to prevent the spread of COVID-19 would not be recommended. Cleaning the environment (cleaning high-contact surfaces regularly) is probably a much more effective way to prevent COVID infections than controlling ambient humidity.
Although humidity control may be helpful, filtration, ventilation, and disinfection will be a higher priority application.
Is fresh air circulating?
Although not definitive for safe air quality, a high degree of air movement, especially a draft, could be an indication of increased ventilation or filtration.
The ideal environment is one in which a lot of fresh air circulates from outside inside . Proper ventilation will remove virus particles from the enclosed space, preferably by ventilating it outdoors, and will bring in fresh air (either from outside or filtered) to replace the exhausted air.
In short, pumping outside air helps dilute any pollutants, such as viruses, in a building.
Logically, open doors and windows are the clearest signs of good natural ventilation. But even with these precautions, air exchange can be inadequate if there is not much of a breeze or if the internal and external temperatures are similar.
Is there an air purifier?
Air purifiers, also called air cleaners, can also help decrease the amount of pollutants in the air, including viruses like COVID-19, in a confined space. In many cases, more viral particles in the air can be removed by filtering than simply by ventilation.
Air recirculation with MERV (Minimum Efficiency Reporting Value) filters 13 or better can provide even greater risk reduction at lower costs.
MERV is the system created by ASHRAE to rank particle filters on a scale of one to 16, where higher numbers are better as they filter more and smaller particles. For reference, ASHRAE recommends MERV 13 (or more) filters to reduce long-range transmission of small respiratory particles that carry the SARS-CoV-2 virus.
HVAC systems have built-in air filtration, but for smaller spaces or places without mechanical systems (like many residential homes), a portable air filter can be extremely effective. However, not all air purifiers are the same. When purchasing an air purifier, first consider the quality of the filter . High Efficiency Particulate Air (HEPA) filters are the gold standard.
In addition to HEPA filtration, some of these devices also offer disinfection as a secondary step to trap any pathogens that have escaped through the filter. Although the most reliable and well-studied disinfection method is ultraviolet germicidal irradiation (UVGI).
However, be aware that some disinfection methods have the potential to create ozone, which can be detrimental to your health. Before you buy, check out dangerous ozone-generating air purifiers.
Is there a carbon dioxide detector?
Carbon dioxide (CO2) is not actually a pollutant, but calculating the amount of CO2 (measured in parts per million or ppm) in a room can be used as an indicator of ventilation per person, as people generate CO2 by breathing . Essentially, more CO2 means more exhaled breath and potentially more airborne viruses.
It is recommended to keep the CO2 concentration of an indoor space at 1,000 ppm. For reference, the outdoor concentration is typically 400 ppm.
A CO2 detector can give you a general idea of what is happening to the air and ventilation, but it is not a perfect indicator. Higher levels of dioxide, even at 1,600 ppm, do not pose a health risk by themselves, and fluctuations in CO2 concentrations, which will likely vary from room to room, are not much of a problem.
How to increase the natural ventilation of a room?
To increase natural ventilation, the following strategies are recommended:
- Open multiple windows or doors, preferably at opposite ends of the space (but not directly across from each other) to increase cross ventilation.
- Open the highest and lowest windows (especially on different floors).
- Use indoor fans and place them in front of the windows, either facing the window (expelling stale air), away from the window (blowing fresh air), or ideally a combination of both.
- Position the fan so the airflow doesn't blow directly from one person to another.
Can you use an air conditioner to increase indoor ventilation?
Unfortunately, most air conditioners only recirculate indoor air.
However, during colder weather, natural ventilation through open windows and doors may not always be possible or practical. In these cases, most commercial buildings use mechanical heating, ventilation and air conditioning (HVAC) systems to pump outside air into the interior.
Since the operation of your HVAC system filters the air as it circulates, it can help reduce air pollutants, including viruses, indoors.
The problem is that we can observe the open windows and assume that there is enough air, but if the ventilation is provided by the mechanical system, we do not have a good way of knowing if it is sufficient.
