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DeltaPlan Ventilation

About aerosols, masks and RIVM - 9354
Samenvatting van het artikel

The virus thrives best in confined spaces without good ventilation, where people are together who normally do not meet (often). Since we only have 4 months till autumn, I submit that the Delta Plan for the HVAC systems should be introduced in the Netherlands immediately.

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DeltaPlan Ventilation

The term DeltaPlan originated in the Netherlands after the great flooding of the Delta of the Netherlands – the south-western part – in 1953 with almost 2000 deaths. It was an integral plan to ensure that this would never happen again. Since then it has been used to refer to large integral plans.

While I was writing this part the message came from the lockdown in Gütersloh, due to the big outbreak in a slaughterhouse. That’s exactly where I’m afraid it will happen – especially in the autumn – in the Netherlands, because WHO and RIVM (the Dutch CDC) continue to deny the -large- effect of aerosols. However, outbreaks do occur and society has to lock up for a while.

This is Koen Swinkels’ database of approximately 1,200 superspreading events around the world. 500 of them concern more than 100 people who became infected during an event.  It is far from complete, but only includes the officially registered superspreading events.

There is a commonality: these events took place in more or less enclosed spaces, without a sufficient supply of fresh air.

Direct contact

The Van Dissels of this world, following in the footsteps of the WHO, continue to claim that also on those occasions the contamination took place via direct contact. If only 1.5 meters distance would have been kept, these contaminations would not have taken place.

Nearly 2 months ago I described in this blog that the major outbreaks in the meat processing industry were due to the fact that the virus can remain in the air for a long time in factories where low temperatures are maintained to ensure that the meat does not spoil.

But no, when it finally broke out in the Netherlands, it had to be because of the living conditions of the workers. Something that was also supplied in other countries.  In this blog last month, I already indicated what major consequences that could lead to, as long as you don’t recognise the real problem. And that is exactly what happened in Gütersloh.

The director of the German RIVM reported yesterday for the first time in the German ZDF journal that aerosols at a low temperature in those slaughterhouses is the cause.

If these conclusions had been reached 2 months ago, the outbreak in Gütersloh would not have taken place and the Lockdown would not have been chosen.

So now we really have to do the best we can, in order not to get similar situations in the Netherlands. And those risks will clearly increase when we enter the autumn (And I don’t completely rule that out during the summer either).

Delta Plan Ventilation

The virus thrives best in confined spaces without good ventilation, where people are together who normally do not (often) meet. Low specific air humidity (below 6g/kg, which at 20 degrees is less than 45% relative humidity) ensures that the aerosols can remain in the air for a long time and then be inhaled. Of course, it is crucial that there is someone in that room who is contagious. And during this summer the chance of ending up in a room with a contagious person will be extremely small.

Natural ventilation, for example two windows / doors that are open opposite each other, provide the supply of fresh air and the removal of air with possible virus particles. During the summer we often have such situations, in order to dissipate the heat. But when it’s colder outside, we don’t do that.

At home this is much less of a problem. Especially if you don’t have others visiting you or people you deal with very regularly. Then the risks are virtually zero. But if you go to a place where there are a lot of people you don’t meet or hardly ever meet, the risk increases. And certainly in autumn or winter.

HVAC Systems

For buildings where the temperature and ventilation are controlled by HVAC systems (and there are many of them), these systems spread aerosols between rooms.  This is a considerable risk at care institutions, for example. And I think that the vast majority of victims in care institutions are infected in this way.

But that risk concerns every place where many people are together: school buildings, offices, cinemas, theatres, event venues, churches, association buildings, shopping centres, hospitals, restaurants.

But at the moment, the good news is that there are now very few people in the Netherlands who are contagious, so there is only a very small risk of infection in any of those buildings. And also, that there are already quite a few HVAC systems, which are set up in such a way that those flying virusparticles don’t get stuck for long and are removed. Those systems are Coronaproof. That depends, among other things, on how much fresh air is drawn in from outside the system and on the quality of the filters in the system.

Plus, there are also many buildings where the virus does not easily get stuck above people. For example due to high ceilings (large volume of space compared to the number of people) and/or how the ventilation system works. For example, I understand that the system in the ceiling of the Concertgebouw’s main auditorium is effective in expelling those harmful aerosols.

Good experts

I myself knew little about HVAC systems, but there are several good experts who provided me with relevant information.  I gave one of them the space to write an article on my blog.

And I received information from someone who had been inspecting those HVAC systems at the Labour Inspectorate for years, which made it clear to me what the core of the problem is. And it’s twofold:

  1. When setting up the HVAC systems, one of the issues is how much fresh air is sucked in from outside. The more that is, the better that is in terms of reducing the chance of being infected.

There is an important term “ventilation rate”: the amount of fresh air sucked in per hour divided by the volume of the total room. If the ventilation rate is 2, then the air in that room is completely replaced 2 times per hour.

Remember that if it is colder outside than inside, the HVAC system has to heat that air. And if the air is warmer outside than it is inside, the HVAC system should cool the air properly. In both cases this costs (a lot of) energy.

So the tendency will be to recirculate the inside air as much as possible, instead of sucking in fresh outside air.

Ventilation rate

That expert told me that in practice the ventilation rate is usually kept undesirably low in order to keep energy consumption low. That would especially be the case in slaughterhouses. Because the temperature has to be kept low there, all the air from outside that is warmer than the desired indoor temperature has to be cooled down considerably.

Increasing the ventilation rate by 2 or 3 can, on the one hand, result in considerable additional costs. He also told us that he regularly came across HVAC systems that simply don’t have enough capacity to bring the temperature down enough.

  1. In addition, suppliers of HVAC systems claim that they can render viruses harmless by means of filters and/or other air purifiers

I can’t judge it properly, but I’m sure that it shouldn’t be difficult to determine very quickly with a task force which of those products/services conclusively succeed in rendering the virus harmless via HVAC systems and which do not.

To really ensure that there is no large second wave in the Netherlands in the autumn and to prevent measures also having to be taken, as is currently the case in the Gütersloh area, we need to set up and implement a DeltaPlan Ventilation.

More important

This is much more important than the 1.5 meter protocols of all kinds of companies and industries in order to prevent the spread of the virus.

Every HVAC system in the Netherlands must be made Coronaproof before the end of October. They must be modified if necessary, or certain additions must be made to comply with the qualification “Coronaproof”.

If that is the case, then everything can be done within those buildings without any restrictions. (I’m sure one shouldn’t have to keep 1.5 meters there either, but that’s of secondary importance for now).

If that is not the case, then there are a number of possibilities to still be active in those buildings:

– Windows / doors open to a large extent.


– The mandatory wearing of mouth protection if you are/will be in that building for a long time


– It is established (especially if there is a large volume of room in relation to the number of attendees, for example by a high ceiling) that the risk of the virus remaining just above the heads of the attendees is small.

RIVM denies

We only have 4 months left to implement this plan. In fact, we have already lost time, because the RIVM denied/ denies that this is important. Ventilation hardly plays a role in the RIVM protocols that have been issued so far. (As I know from my contact with my daughter’s primary school). It is almost only about the 1.5 meters and personal hygiene. And read this again, only 1 month ago.

Every day that the RIVM still refuses to put this subject on 1, is an extra day, which may result in extra casualties in the Netherlands in the autumn and winter. that increases the chance that we will end up in certain lockdowns after all.

So my concern is not only that ventilation should be set to 1, but also that the Delta Plan for the HVAC systems should be introduced in the Netherlands immediately. Perhaps the people who are now active in removing houses from the gas can also become temporarily active in this Delta Plan.

And I sincerely hope that the experts I have contact with will be able to play an active role in the design and implementation of this Delta Plan. Because when I read how things went in the first few months with mouth caps, respirators, etc., I am afraid that we will only have started when winter arrives.

I hope that those who are responsible for locations with an HVAC system will also take their own responsibility. And don’t hide behind the fact that it’s not (yet) in RIVM protocol. Even with simple means, a lot can be done in the short term, especially with the nice weather outside.

So ventilation, ventilation, ventilation.

You have just read: DeltaPlan Ventilation.

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