Data compiled by the world health organization (WHO) shows that poor ventilation can lead to an increase in virus transmission. As such, improving ventilation indoors should be considered an important step in reducing the spread of viruses such as COVID-19.
This article covers three simple steps to improve indoor ventilation and lower the risk of COVID-19 virus transmission.
1. Open up Doors and Windows
Opening a door or a window is a simple way to improve indoor ventilation. Data shows that opening windows in a typical home can double ventilation rates. What’s more, scientists found that opening windows in old-fashioned style hospitals with large windows and high ceilings increased air changes almost 20 times.
Scientists in the US also tested the how ventilation rates changed when opening the front door of a typical home. They found that opening the door 60 times in an hour also doubled the ventilation rate.
Opening a window or door is a simple solution, however it does have several disadvantages. Opening windows makes it difficult to control the indoor temperature. In places where there are high levels of outdoor air pollution, it can also let this into the building. Finally, many offices have windows that cannot be opened.
Effectiveness: for typical homes, opening a window can double ventilation rates (from 0.2 to 0.4 air changes per hour).
2. Turn On HVAC & Central Air Systems
If opening a window isn’t an option, then turning on the central air system or ‘HVAC’ could help improve indoor ventilation. HVAC systems typically take outdoor air, and pump air into the all the rooms inside the building.
They also suck out air through exhaust vents, which could help lower the concentration of viruses in the room, by sucking them out.
HVAC systems, however are complicated. There are reports that HVAC systems can spread viruses such as the coronavirus. This happens because they move airborne droplets from an infected person/area around the room or the building. ASHRAE, on the other hand, explains that proper use of ventilation can reduce the airborne concentration of SARS-CoV-2 and thus the risk of transmission through the air.
For HVAC systems that recirculate air, they should be fitted with air filters to reduce the chance of transmission.
Effectiveness: HVAC systems can typically provide up to 5 air changes per hour, greatly improving indoor ventilation. However recirculation should be reduced/eliminated and central air systems should be fitted with filters to avoid the risk of further transmission.
3. Install a HEPA Filter Air Purifier
If there’s no central air system available, then installing portable air purifiers is a third option to increase ventilation and . While air purifiers do not directly ventilate a room replacing the air in the room, they can do something equivalent by removing viruses from the air. Air purifiers have what’s known as its equivalent air changes per hour.
Calculating how much an air purifier can increase the ventilation is fairly simple. First, find the purifier’s airflow rate, either in m3/hr or cfm. Then calculate the room’s internal volume.
As an example, the Smart Air Blast air purifier has an airflow of 1800cbm/hr (not to be confused with CADR). A 100sqm room with a ceiling height of 2.4m has a volume of 240m3. That means, the Blast is able to provide:
1800/240 = 7.5 equivalent air changes per hour.
Air purifiers with HEPA filters are a simple solution to removing viruses from the air. The best thing is, air purifiers don’t need to cost an arm and a leg.
Caveat #1: The position of the air purifier is especially important in maximising equivalent air changes per hour. If the purifier doesn’t help recirculate the air in the entire room, then its equivalent air changes per hour is likely to be much lower.
Caveat #2: There are some concerns that viruses can survive on HEPA filters and be re-released into the air, however data shows that the COVID-19 coronavirus and other enveloped viruses typically die within 72 hours on cardboard.
Increasing Ventilation isn’t a Bullet-Proof Solution
These are three simple ways to improve ventilation in places like homes, offices, schools and hospitals. However, increasing a room’s ventilation rate shouldn’t be taken in isolation. Practices such as washing hands, wearing masks and reducing contact as advised by government agencies should still be follows.
Paddy is the CEO of Smart Air, running operations from Beijing. He has a Masters in aeronautical engineering from Bristol University, UK having specialised in aerodynamics. An advocate for open data, free information and transparent business, he spends his spare time promoting honest business and social enterprise.