Protecting your Building
Airborne viruses

Reducing Risk in Buildings

Created Monday, 21 June 2021

As the world changes with the Covid 19 pandemic, new guidelines have been introduced in Europe with regard to building safety.

  • Guidelines overview from REHVA
  • Considerations for existing systems
  • Examples
  • Filtration and other solutions
  • Do HVAC Systems need to be upgraded
  • One piece of key advice which applies to all

Our guests this month are REHVA board member Atze Boerstra and Camfil’s Tobias Zimmer.

Atze Boerstra serves as a board member with Rehva, the Federation of European Heating, Ventilation and Air Conditioning Associations founded in 1963. His own company, BBA Binnen—milieu in the Netherlands, are a world leading consultancy firm specializing in the indoor environment and its effects on people.


Tobias Zimmer, the Vice President of Global Product Management & International Standards at Camfil, has 17 years’ experience working in the ventilation industry. He’s also an active member in several industry associations, such as Eurovent and EVIA. Tobias is also deeply involved in the development of international Standards in the fields of air filtration and building ventilation, both at ISO global level and CEN on the European level.

Read the Transcript

Dusty Rhodes  0:40 

Hello, and welcome to Let's talk clean air where we find out more about how clean air can affect the quality process for you and the workplace. This month as the world changes with the covid 19 pandemic, new guidelines have been introduced in Europe with regard to building safety. We'll be finding out more about those and how they might change the way that we do things. My name is Dusty Rhodes and joining me is Atze Boerstra and Tobias Zimmer. Atze serves as a board member with Riva the Federation of European heating, ventilation and air conditioning associations founded in 1963. His own company in the Netherlands, are a world leading consultancy firm specialising in the indoor environment, and its effects on people. Tobias Zimmer is the Vice President of global product management and international standards at Camfil. He has 17 years experience working in the ventilation industry. He's also an active member in several industry associations, such as euro event and Evie a. Tobias is also deeply involved in the development of international standards in the fields of air filtration and building ventilation, both at ISO global level and Sen on the European level. That's it if I can start off with you. Could you tell me more about Riva and their role in the European industry?

Atze Boerstra  2:08 

Yes, like you said, I'm one of the board members of reverse the European Federation of the heating, ventilation and air conditioning associations. So think, for example, in the UK, SMC organisations like CIBSE and umbrella organisations for organisations like that. We call ourselves the voice of the European HVAC, engineering consultants, maybe manufacturer, and we try to put the subject of healthy energy efficient productivity enhancing HVAC systems on the on the agenda in Europe.


Dusty Rhodes  2:44 

Now, you've recently developed a guideline for building ventilation in regards to COVID-19. Can you tell me how the guidelines came about?


Atze Boerstra  2:54 

Yes. When the first signal scheme, especially from Asia, I remember the issues with the cruise ship where we had COVID outbreaks, some of us started to contact each other within a river, for example, Professor, who has been on river board for a long time. And we also started quite soon, I'm talking into February, already, beginning of March, we started to reach out to some of our friends in Asia, for example, in Hong Kong, who we knew had experiences with the previous SARS epidemic. So already at that time, we started to communicate what's happening, is this airborne? What can we do on the side of assistance, heating, ventilation and air cleaning. That's basically how it started. And within a couple of weeks, we got to the point where we had written down and talking about the first version of the revised guidance document, we had written down what we thought was good guidance for especially existing buildings on how to adjust your heating, ventilation and air conditioning systems.


Dusty Rhodes  4:00 

Now, we've had many viruses in the past, why has it taken COVID-19 to get these guidelines together?


Atze Boerstra  4:07 

Yeah, it's that that's a very interesting question. Because there are other diseases, think, for example, influenza, and we know of those diseases there. They also at least partly spread to the air. So it does make sense when you discuss, for example, about ventilation requirements in buildings, to not use look at impact on energy or impact on comfort on smells and buildings, but to also look on how ventilating more or less impacts the spread of infectious diseases inside, and I'm also on the same committees. And so we talk about this issue a little bit, but of course, it's covered. We are kind of forced with the whole community to really think about, are we ventilating our buildings the right way and should we maybe adjust the ventilation standards that we use, so it's kind of it helps to put the Subject on the agenda again, even though already in the past, we had other diseases that that's on paper, at least, should ask for more attention to this subject.


Dusty Rhodes  5:11 

So COVID-19 is really kind of just the sheer size of it has given us focus and a reason for getting these things done now. And we're able to take what we know and are learning about COVID-19. And with previous viruses, and building all of those learnings into these guidelines. Can you tell me what are the key considerations that are made within the guidelines?


Atze Boerstra  5:34 

Yeah, in in the last version of the river guidance document from November 2020, we, we now describe 15 different actions you can take to make existing buildings better, more healthy, less risky, in terms of ventilation and infectious diseases, especially COVID. I'm not going to tell them all 15. But important ones are related to dilution, making sure there's enough fresh air coming in individual spaces. So if there is by accident, somebody who spreads the virus, then what the other people inhale, the concentration is relatively low, because you ventilate a lot, you dilute the air in the right amount. So some of the advice is related to the amount of fresh air supply. Some of the advice is related to, for example, the use of operable windows, because sometimes if, if you have a meeting room, which is designed for a few people, and you're there with a lot of people, it makes sense, maybe between meetings for five or 10 minutes to open a window here. People like us have a background in mechanical engineering, they normally only think about mechanical systems. But often the combination of good facades, operable windows, and good mechanical systems works very well. So we talk about that. We also talk about the use of air filtration. In some situations, it's difficult to ventilate, really a lot thing, for example of a meeting room in a nursing home and people will in winter get a lot of draught problems. So in some situations, you know, people are they're sitting together, we have to protect them against each other. And then you additionally can do something with filtration. So we have some recommendations about that. And I think those are the main ingredients.


Dusty Rhodes  7:20 

Are there any recommendations around the fresh air supply? Like? How many changes should we aim to achieve?


Atze Boerstra  7:27 

Yeah, that's a typical question that's easier asked them answered. And this has to do with the fact that it depends very much on the situation, if you have a situation where there's everybody's quiet, we know when people are quiet, and he should still have a low metabolism. They spread much less aerosols than for example when they when they talk a lot. And it's even more and people shout. Think about a sports venue, for example, when people seem to think about the church. So it's very much dependent upon what people are doing on the size of the room, if you have a relatively large space, it takes time before it fills up with aerosols with bio effluence. So it's very difficult to give just one number everybody asks about that, in terms of how much ventilation you should ventilate as a minimum. Having said this, there are European standards that say that in a class a situation you should ventilate at least 10 litre per second per person. That's about 36 cubic metre per hour per person. And I've seen a few academics that had analysed some outbreaks. And where they said, well, the, you should translate at least something like that this this template per second per person. I personally think it doesn't hurt if you go a little bit higher. And of course, from an energy point of view, especially in winter, or maybe middle of summer, you want to limit it. But to be honest, I've done some calculations myself, there are ways you can calculate infection rates to the air. And I found that it's in certain situations you need way more than then even this 10 or 20 litre per second per person, if you if you are there for a really long time together and you shout and sing etc. So there's not just one number that that that makes you safe by definition.


Dusty Rhodes  9:23 

You say that the guidelines are there are 15 different recommendations in there. Where can we find the the entire list of guidelines and recommendations?


Atze Boerstra  9:32 

Yeah, if you go to the REHVA website, which is, you spell this R e, h, VA, and So And then you'll see right on the starting code page, you'll see maybe a button COVID information and then you can find not just the guideline I just refer to, but also some other background information about the COVID and the ventilation.


Dusty Rhodes  9:59 

Tobias If I can bring you in on our chat here, air quality is incredibly important, from your point of view with Canfield, what levels of filtration are recommended.


Tobias Zimmer  10:11 

Now, that's also not that easy to answer, it really depends on what kind of situation Do we have or what kind of air supply to the room do we actually have, which was also mentioned a little bit buyouts already. So if you're talking about outdoor air being supplied to the room, then the actual risk of COVID-19 being spread by the air is relatively low. But by getting the air from the outside, you may have high levels of air pollution coming from the outside depending on your location. But means in all the cases where your air supply is 100% outdoor air supply to the room, standard filtration levels are absolutely sufficient, and standards of filtration levels, whatever that case mean, filter levels, according the European guideline for 23, which gives you guidelines on filtration levels depending on your outdoor air quality. So in practically that means for an office building, the supplier should have a filter of at least EPM 150, according ISO 16 890, in bigger cities, it will be more a level of EPM 180 for the filtration system. So for instance, if you have an office building in the centre of London, you will definitely need a protection of EPM 180. To be safe long term. And by building that you could for instance achieve was a two stage filtration of two APM 160 photos in a row, which is quite good and industry standard. If on the other hand, we have a situation where you bring recirculated air central recirculated air to the room, it looks completely different. Because in that case, the air from one of the rooms or from one office won't be transferred wire or the central risk regulation system to the other rooms in the building. That means the risk of spreading aerosols was a virus in it is significantly higher. So worst case, just one infected person in one single office code spreads the aerosols over the whole building. So in those cases, there's higher need for filtration. And the best solution in those cases would actually be having HEPA filters, meaning h 13 to h 14 filters, according to Ian at 22 in the recirculation system, but just doing that just adding the filter is technically not always that easy.


Dusty Rhodes  12:52 

A lot of people will have their air infrastructure in place, how possible is it for them to upgrade to get them to the new standard that we now require?


Tobias Zimmer  13:04 

I gamble it really depends on of course, it depends on the system on the other side of depends of what kind of air supply Do you have. So if we're talking about again, about supply air from the outside, it is normally possible in the utmost applications to bring supplier photos to a decent level. So it can be normally done without any significant increase of the pressure drop. That's normally the critical point in changing the filter. This works the upgrading without increasing the pressure drop significantly, simply by choosing a high quality air filter. Those high quality air filters should be EUROVENT certified ePM1 filters was a goal this year of an energy rating just to ensure low pressure drop and low energy consumption over time. And using such a filter doesn't really create more pressure drop to the system than a lower quality filter was lower for the class. So in those cases, it's relatively easy. It's getting us set is getting more difficult if you have a central recirculation because many recirculation air systems are really not designed for the use of hyper focus, which will be tactically seeing the best solution in this case to protect against COVID. Because these hyper filters have a relatively high pressure drop, and that could be too high pressure drop actually for the system, resulting in either too little error going into the rooms, which is of course also not a good solution because then you reduce the amount of supplier. In addition, many of these systems actually may not build the mail people tight enough so that the error might bypass the habit filter, resulting again an increased spread of the virus. So here it's technically a little more difficult. So if you have one of those cases where it's difficult to upgrade to HIPAA The best solution will be, first of all, to turn off the recirculation error completely and increase the supplier. If that is not possible to get enough airflow in your building ban, you should actually see what is the maximum upgrade your system can take. So if then you should at least try to upgrade the recirculation air filter to filter according ISO 16890, which will be a minimum efficiently See, you then have ePM1 80 percent. And there are such air filters available on the market. So there's for instance, on ePM1 85 filter that still has a very low pressure drop. So it can be used in nearly every existing central recirculation system. Again, to ensure that these filters really hold their promises, so it's really EPM1 95 efficiency, make sure it's your event certified, make also sure that it comes with an Eurovent Class A plus or a which guarantees a very low pressure drop, not only in the beginning, but over time. So it will really work in your system.


Dusty Rhodes  16:09 

I'd say can I come back to you? Where's it? What's your point of view then on filtration? Well,


Atze Boerstra  16:14 

in addition to what Toby has said, one thing I think it's very important to point out and Tobias has already kind of said it is that it very much depends on the system you have when we in March, April had discussions with colleagues from other continents, North America, Asia, it took us a while to find out because if you talk with somebody from Scandinavia and Germany or the Netherlands, what you what you tend to think about, for example, in an office environment is that you have a system, it's not an all air system, you do have ducts. This is just to make sure that ventilation, air goes through different spaces. But your temperature is controlled by radiators in winter, or maybe climate sealing or the central cooling unit in summer. And in those cases, it's normally quite easy not to turn on the recirculation. And so to avoid what Toby has described, but then we talked with some of our colleagues from North America, and they said, and the UK is maybe a little bit in the middle, they said this is just not possible, because we have all air systems. So we just need this this massive amounts of air to go to the building. Otherwise, we cannot make the right time, kind of temperature and winter and summer. So if you do have an all air system, then you kind of you don't have a choice, you still need to keep the ratio on. And then like Tobias and  I said, you have to really look at what kind of filter do we put on the in the return ducts before air is put back into the building. Another remark is, when we talk, especially with our colleagues from Asia, they told us be aware that in some situations, think of big cities in China, maybe also Delhi. And also of course here and there in Europe and in North America, the outer air is so polluted that it's easy to say that you should keep systems on the maximum setting and that you try to maximise the amount of fresh air coming into the central air handling unit. But then, of course, you bring in much more fine particles from outside. So in those situations, you really have to maybe change your outdoor air filters faster or put in a better better other air filter. So you really have to think about where is my building? How is the other air quality there? Is it an all air system or not? Can I shut off the recirculation. So no easy answers here?


Dusty Rhodes  18:30 

So what do you do then if you have done all of these things, as you suggest, and then you just come to the realisation that the system that you have now cannot be upgraded what are the options?


Tobias Zimmer  18:42 

So what can you do so in addition to the air filters in supply, air and central air circulation, there is also the other option or an additional option of using decentralised or even mobile air purifiers in the room. So it's recommendable everywhere where a proper filtration of the air is otherwise difficult. So if you use these mobile air purifiers, it's extremely important that those purifiers are equipped with hyper filters. So real h 13 h 14 filters because there's also some other systems on the market, which are more questionable. But having a real hyper filter, you can be sure that the filters are able to reduce the aerosol concentration in a sufficient way. So being a little bit more specific. What's the best sitio solution in a in which case it really depends on the specific case. So what type of recirculation are we actually talking about? out dimensional already, there's various versions of it. And there's not only central recirculation, so if it's centralist recirculation the only option is upgrade your filters or turn it off completely, because there is a high risk of spreading viruses over rooms. And then if it doesn't work with the recirculation, upgraded filters, then use mobile air purifiers. But there may be other cases where you have  recirculation, so called split units. And but it might look totally different. Because the other than the central recirculation is split units would only create so called secondary air, so the air is only recirculated in one single room. But of course, it has a much lower risk of virus spread than a central recirculation for the whole building. So if we're talking, for instance, about a small room or a one person office, then there's actually no risk because there's one person in the room and the recirculation will only scratch his own virus worst case, to himself. But of course, if the room is getting bigger, if it's an office with several people in it, this split units will actually spread the virus from the one infected person over the whole room to others. So here we see bigger risk. And these split units normally cannot be upgraded to good filtration, they're really not prepared for it. So in those cases, and where it's not possible to turn off the split units for temperature reasons. Again, the best solution would be the use of one or probably depending on the room size, multiple room air purifiers to do additional research of the room error and decrease the aerosol concentration


Dusty Rhodes  21:35 

I see. Let me go back to the guidelines because our overriding concern really is people getting back to work in offices and schools and of course, other facilities. And what would you say are your three key recommendations, just making sure that people are safe?


Atze Boerstra  21:53 

Yeah. And maybe general remark to answer that question that I would like to make first is that, of course, if you want to if people go back to the office, and we know if this specific virus that we have right now that people might carry the virus without having symptoms. So you should always assume that the other also persons without symptoms might carry the symptom, especially if your infection rate in your region is high. If you want to try to make the environment the work environment as safe as possible, you should look at more than air filtration, ventilation, etc. And let me be very clear about it. So we have the standard measures, hand washing, staying home if you have symptoms, keeping distance, etc. So these things are important and ventilation, air cleaning, etc are important. So you really have to see it as a combination. And the Secretary General of the World Health Organisation gave officials I never know exactly how to say his name. He said this in a video. I think in September, he said, That's not discussed about whether hand washing is more important than keeping distance or ventilation. Let's do it. All right, he literally said do it all. So if people ask me I want to reopen, for example, an office or a school, I want to make sure things are safe. I tell them do it all and make sure people wash their hands. Try to keep the distance where possible. Make sure you ventilate, as much as reasonable as possible with the existing systems. And that's maybe one specific recommendation I can give to answer your original question. A lot of existing situation today, they have quite a high capacity to ventilate a lot at a room level. But the settings are such because of energy reasons, for example, that they don't do the maximum that they can do. They maybe are operate only on 30 or 40%, for example, because they have a demand control system that reacts slowly on co2 concentration. So it takes maybe an hour before the system goes to the maximum setting. And that's one of the key recommendation will also give reverted if you have demand control systems, co2 regulator systems, make sure you change the setpoint for this try to make it as low as possible. So just a little bit over the outset, outside co2 concentration. So let's say 450 500 or something. So as soon as the system detects, there's one there's persons in the room and more than one because one cannot infect itself, then it should start operating. So that's something you can do easily in existing systems. If you do have like energy regulated, fresh air supply at room level, and this is something that doesn't really cost that much money, it can easily be done. And I see a lot of mistakes with that still.


Dusty Rhodes  24:41 

Okay, well there is definitely lots and lots that can be done to make our buildings more safe as people do return when or when they eventually do return back to work. For now though. Atze and Tobias Zimmer, thank you both very much for joining us. Okay, thank you.


Tobias Zimmer  24:57 

Thank you. It's a pleasure.


Dusty Rhodes  24:58 

If you would like to find out more about What we've been talking about today just follow the links in the show notes. You'll find those in the description of this podcast on your phone, or whichever device you're listening to us on right now. They include links, contact details and anything else that you might need to get the information you want. Our podcast today was produced by camfil, a world leader in the development and production of air filters and clean air solutions. You can find out more at Cam do join us next month when our let's talk clean air podcast we'll look at how air quality can affect what we eat and drink the challenges facing food and beverage production facilities. To get an automatically just click the subscribe button on your player right now. Until then, for myself, Dusty Rhodes, thank you for joining us today and thank you for listening.