FAQ - Frequently Asked Questions about ventilation and COVID-19

31 August 2020

Lately, due to COVID-19 there has been much attention for ventilation. Many different studies have now been published about airborne spread of the virus. Partly because of these recent insights, the ventilation guidelines are being updated regularly. Yet that leaves the recommendation unchanged to ventilate as much as possible and to supply the maximum flow of fresh air to recirculation systems. Recirculation means that the exhaust air is reused rather than carried off outdoors.

Different ventilation system types
You should realise that many different types of ventilation systems exist, each with their own risk of spreading viruses. Recent reports about the possible spread of the coronavirus through ventilation, are mainly about larger systems used in public buildings. Those may include offices or nursing homes, or at least buildings where several people from different households are together for an extended period and where a recirculation system is used. In such cases, there might be a risk of spread of the virus through the ventilation system.
 
For dwellings: ventilate as much as possible
However, for dwellings, only one household is involved; a family or group of people who live together in one home. Of course there is a substantial risk that these people infect each other, but the ventilation system does not increase that risk. That is because most dwelling systems do not use recirculation and only supply fresh air and carry off the used air. Indeed, intensive ventilation reduces the risk of contamination because the indoor air is diluted as much as possible with clean outdoor air and, consequently, more used air is carried off.
 
Use outdoor air as much as possible
However, there are systems for dwellings and non-residential buildings that partly use recirculation, for instance air heating systems. Again it applies that in the case of dwellings, people of one household are involved for which the risk that they infect each other through direct or indirect contact is much greater than the risk that infection takes place through the air heating system. For public buildings, such as cinemas or swimming pools, we observe the same ventilation guidelines and we also recommend to introduce as much fresh outdoor air as possible and to limit recirculation. This means that in all cases we recommend to minimise recirculation and to use outdoor air as much as possible.
 
We will answer most of the frequently asked questions below. In doing so, we always adhere to the same ventilation guidelines. Our advice for all systems is: ventilate as much as possible and prevent or minimise recirculation.
 
  • Can aerosols pass on the virus through ventilation systems?
Lately, there has been much attention for aerosols as potential transmitters of the virus. Aerosols are small dust particles or drops of moisture which are light enough to hover in the air. Although scientists say that it has not yet been established beyond any doubt that aerosols have really contributed to the spread of the coronavirus, we just like to be sure. To limit any spread by aerosols, we recommend to ventilate with outdoor air as much as possible to dilute and remove the aerosols.
 
  • Should I switch off my HRV unit (Renovent or Flair) because of the coronavirus?
No, you don't. On the contrary, it is recommended to ventilate as much as possible. When ventilating, you are cleaning the air by removing stale indoor air and replacing it by fresh air from outside. Outdoor air contains no viruses at all. So increased ventilation means that more stale air is removed and the polluted indoor air is diluted with clean outdoor air. That reduces the risk of transfer through the air by moisture droplets or aerosols.
 
  • Should I exchange the filters of my ventilation unit more often now?
Ventilation systems with mechanical supply from outdoor air such as HRV systems feed outdoor air into the home through a filter. This filter prevents any dust from entering the home from outside. Outdoor air does not contain any viruses, so there is no reason to replace the filter more often. An HRV unit has two filters. The filter in the exhaust air protects the device from pollution with household dust from the indoor air. If the indoor air contains virus particles, they will be carried off to the atmosphere or get stuck on the filter, but there they don't pose any risk of contamination. This means that the filters in the HRV unit have no positive or negative effect on the spread of the coronavirus and do not need to be replaced more often.
 
  • Can the coronavirus establish itself in the ventilation unit filter?
Viruses can only multiply in a human or animal host. Viruses that end up on the filter, only stay there for a short period before they perish, so the filter will never be a source of spread of the virus.
 
  • Do you have a filter that kills viruses/bacteria or are there filters that eliminate viruses?
We developed a filtering method for our ventilation systems to catch the smallest dust particles, the Pure induct. The Pure induct is placed in the air supply of the mechanical ventilation system and filters the incoming outdoor air. Since viruses are particles as well, any viruses will also be filtered from the air. However, we recommend the Pure induct for filtering for instance fine and ultra-fine dust and pollen, to prevent hay fever, and not for filtering viruses, because the outdoor and does not contain any of those.
 
  • Does an HRV system carry a risk of spreading the coronavirus and does that apply to all system types?
On the contrary, the risk is reduced because ventilating as much as possible has a positive effect. Airborne viruses in moisture droplets or aerosols are diluted by the supplied fresh air and, eventually, they are discharged with the exhaust air. It is recommended to ventilate as much is possible.
 
  • Does an HRV system increase the risk of catching covid and does that apply to all system types?
Several types of heat exchangers are discussed in the media. There has been discussion about the possible transfer of the virus through exchangers of the ‘thermal wheel' type. Brink does not use this heat exchanger type. In Brink's plate heat exchangers, supply air and discharge air are separated from each other for the full 100%.
 
  • Does the situation when using the Multi Air Supply system differ from conventional HRV systems?
Our Multi Air Supply system uses the corridor or the stairwell to distribute the HRV supply air throughout the home and to discharge the used air through the wet areas and kitchen. An Indoor Mixfan blows used air from the habitable rooms into the corridor. Otherwise, it is comparable to any other HRV system. Just like with any conventional HRV installation, the various habitable rooms are interconnected as well. As long as the system is used within one household, just like any other regular HRV system, it does not increase the risk of infection but, on the contrary, ventilation reduces the risk of mutual infection. Student flats with communal areas are also considered single households and there too, a Multi Air Supply system contributes to healthy ventilation.
 
Any other questions? Do not hesitate to contact us.
 
Our answers are taken from the guidelines and recommendations by RIVM, the Dutch National Institute for Public Health and the Environment. Therefore, we recommend to regularly consult the website of this Institute for the most up-to-date information.