ASHRAE ventilation increases to combat COVID?

[232gulfstream]

I keep hearing about this and keep getting lost in article after article but is there any new standard people are using? Our approach recently has been to reduce OA and provide bi-polar ionization along with higher MERV filters in the air handling equipment. Seems like increasing OA is going to burn a lot of energy and result in much larger equipment and so on and so forth. So what is everyone doing these days?

 

[3DDave]

AFAIK the risk of transmission increases with dwell time and being downstream of an infected person. I have seen no indication of re-circulation changing the risk, but if you can trace sneeze or cough particulates and those are entrained through a population, the rates go up. I'm not sure how OA would affect the situation.

Unlike Legionaire's, there is no build up capacity in the air handling - Covid doesn't colonize that environment.

It's been vexing because the transmission rate from person to person is generally low (thankfully) which suggests that the virus is delicate and prone to malfunction within a relatively short period, particularly when exposed to UV as it is out-of-doors. Obviously direct contact is bad - sharing door knobs, sign-in/out sheets and pens, handshakes, et al. If the period is shorter than the recirculation and particularly if anti-life (filters and UV and electrostatics are used) I don't see how outside air improves that situation.

A similar problem has been seen in hospitals where changing the airflow in the rooms changes how bacteria are carried to patients and to other rooms. If the air is set to blow over contaminated surfaces and then circulates around the room, say towards faucets, bacteria can reproduce in the faucet, ready to be flushed onto patient's and staff hands, and then transferred to injury sites or into the nose and mouth. Blow the bacteria the other way and sterilize the air on the way out and the situation is improved.

I think there was one hospital that had air recirculated through the laundry area spreading every disease germ found in the patient population, due to contaminated bedding held to be washed, to all the patients, a number of whom contracted from among those various diseases, seemingly spontaneously.

 

[miningman]

IMO, the efficacy of UVC light is not being recognised. Why this is, I do not know. All the concerns about eye and skin damage are eliminated by mounting the light units in the return air ducts of a conventional HVAC system.

 

[232gulfstream]

Very interesting. We have specified UV germicidal lamps in air handling equipment years ago but since that only targets the air moving past the light it was thought that ionization was a better approach since we are producing ions in the AHUs supply air system and distributing them into the space where they can search out and neutralize contamination.

ASHRAE IAQP method has been allowing us to cut OA in half if we provide ionization. Which we have been doing and having great success with and saving clients money and energy by being able to downsize equipment. Yesterday I had a local sales rep tell me now ASHRAE is saying more OA is what is required. That comment made me do some more digging.

 

[3DDave]

I skimmed the ASHRAE recommendations and it looks like they are treating it like they would dust or, for example, bacterial spores. In other words, as a disease/contamination with infinite durable span.

That's a really conservative approach and fighting that reasoning is tough. "If it saves even one person..." neglecting that money not spent on that might buy automatic doors (no handle contact), electronic non-contact badging (no sign-in/out or shared pens), or more paid sick leave so Mr. Sniffle and Cough can stay home. I also recognize that those are areas ASHRAE cannot control so they are doing what they can.

I hope that ASHRAE is working with bacteriologists and virologists and not merely detecting particles but looking at the effectiveness at stopping contagion. Not every room needs to be a Wildfire lab to be safe enough.

 

[232gulfstream]

Great stuff Dave. My head was spinning trying to find these new ventilation rates. I will stick to what we have been doing. Thanks.

 

[EnergyProfessional]

If you look at the ionization documents, you see the ions decay very quickly. Unless you are right by the diffuser, you likely won't see much effect.

Air is exhausted from the bathroom (where many people "meet" and once air moved from an office supply diffuser to the bathroom, there sure are no ions left. So it is a bit better, than UV (which only works where the lamp is), but not that great. But rooms where I really encounter many strangers it isn't helpful unless those spaces get dedicated ionization units.

Most transmission is from person to person exhaling and inhaling. Unless you create windy conditions like outside, it won't matter much how much you over-ventilate. So you still need distancing, shields, and masks. I assume we are not talking about ventilation rates 10 times the ASHRAE rates.

Imagine a person smoking 10 feet away. Only if you provide enough ventilation that no one int he same office would smell the smoke, you also have enough to protect from viruses. the aerosols and PM from the smoke move exactly the way an exhaled aerosol with virus moves. I can smell a smoker even outside 20 ft away unless I'm really upwind. So this is the challenge of how much ventilation you would have to provide if you wanted to fight virus transmission with added ventilation.

And with vaccines available, do we really need to change ventilation systems? In some months even small children can get vaccinated..... Probably would be good to think about it regardless for the next pandemic. But unless codes and standards change based on actual science, I wouldn't just make the decision to arbitrarily increase rates.

As for what to design for, whatever code requires, or ASHRAE. Unless the owner has some special wish and pays for it. Increasing ventilation has a huge equipment, space and energy penalty.

If you change your design based on last year's recommendations, where do you start? One week masks were bad, next week masks were mandatory. One week going outside in a park was bad, a week later it was good. I think we should wait a year and really look at what actually happened and decide based on science. Or the powers of ASHRAE and JHA should do that.

The architecture of a space probably has more impact. And changing workflows to more remote work will be much better than what HVAC ever could do.

 

[IRstuff]

A certain level of dwell time is required for UVx annihilation of SARS-COV2; moving air makes that ridiculously complicated.

One might think that return air ducts at floor level would be better than ceiling level, since that keeps the virus moving away from bodily orifices.

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[3DDave]

The mask use policy change was initially about the drain of N95 masks from healthcare professionals to everyone, when there was insufficient supply. Later it was discovered that while masks are not generally a good barrier to getting it, it was a substantial barrier to giving it to others and with the difficulty of knowing one was infected, widespread use was needed to catch cases of those who did not know.

Not sure about parks, but at the outset there was no information of just how contagious and how persistent Covid was, so the emphasis was on the better too much concern side.

The direct methods of investigation to determine the values of all the variables are unethical and widely frowned upon. So only via observational study is available and from that conclusions about the disease shift. In addition, changes in supply availability also can change what is the best current thing to do.

It seemed like a really bad sign when China, significantly sensitive about its appearance to the outside world, let out that it was walling off entire cities and welding shut doors on apartments. Whatever they do on human rights, they tend to keep it quiet and this event they allowed information to exit.

The US should have put everyone entering the country into 2 week quarantine on entry. Instead passengers on international flights were allowed to spread the contagion to ground crews and airport employees (who went home and took it to their friends and family before coming back to infect other plane-loads of people) and then continued on with other flights across the US. If I wanted to create a policy to spread a disease with maximum effect that would be my choice.

The present problem across the world is that the little bug can be augmented by evolution. Viri are not substantial and prone to breaking and incorporating other components, and it looks like there are already new versions that are more effective at spreading, are hitting younger people pretty hard, and for which the present vaccines may not be effective at generating a useful immune response.

Humans aren't to the Spanish Flu or Black Death situation this moment, but the more quickly and certainly measures limit the number of humans that these variations can develop in the better. It's why firefighters just keep pouring on the water long after most people think the fire is out - just one little ember in the wrong place and boom - another huge outbreak from fire or disease.

My crystal ball says this isn't over for the next decade, with odd outbreaks of citywide proportions on a regular basis through most of it. It also says at least two or three new vaccines will be needed to take on whatever develops in any of the billions of people somewhere on the planet, but the tech to create them and then produce them will get much much better.

Right now that major spot is India where a political candidate anxious to reassure people all was well lifted restrictions just before the election. It worked. People were reassured and they elected the guy. They now have a million new cases a day and burial services are outstripped and it's a perfect location for one little transcription error to maybe make things much worse. This video explains the various forces at work:

https://www.youtube.com/watch?v=DyXq88MrAVQ

Back to ventilation - I'd like to see top down air supply with floor level full perimeter air returns so particles are carried down and generally kept in a boundary layer at the floor and limited head-level horizontal flow. Coanda can be medicine's friend. Unfortunately this means big changes to building architecture. I suspect getting this to work will require a lot of work and retrofitting is not easy. However this is applicable to all respiratory contagious diseases so even when Covid is gone, it will remain useful for a very long time.

 

[MedicineEng]

I think that the jury is still out on the OA effect on the COVID spread inside buildings. I believe that the reasoning is that if you have COVID infected people inside a building and the HVAC system returns that contaminated air and spreads it to other areas, it might increase contamination rates. Not sure if there is any scientific base for this claim in "normal" venues (not Covid infected hospital wards).

Just as FYI, in the country that I work (not US) the government requested that the ratio of OA air to public spaces to be 2 air changes/hour.

 

[nuuvox000]

Until ASHRAE guidance comes out, it's mostly speculation. However, IAQ is accomplished through dilution (outside air), extraction (exhaust), and filtration. If you get all of those correct then your building is in pretty good shape.

 

[EnergyProfessional]

All the added ventilation and filtration and ionization, UV etc. do is limit spread from one room to another via return air. And it isn't even sure this is an actual transmission path to begin with. It takes a reasonable viral load to infect someone. So if you have 10 offices and one infected person in one office emits some viruses, there is only a miniscule amount going to the other offices. Viruses also don't survive long outside a human (I know, they are not really alive to begin with).

All the measures will do exactly zero or near-zero to prevent transmission from person to person that are a few feet from each other in the same room. Especially rooms where people don't have the luxury to be in separate rooms, like hallways or bathrooms. So if we would build our offices to be hospital-grade, we need to get rid of corridors and bathrooms used by more than one person.

With vaccines available there isn't really someone who actually demands better COVID protection in buildings. the people who care about COVID, got vaccinated, and the ones who didn't don't really care enough that they would care about added ventilation. I know, children under 12 don't have a vaccine, yet, but probably before you can design and upgrade a new ventilation system there will be a vaccine.

All we can do is speculate about the next pandemic.

 

[MedicineEng]

"Everything has to change so everything can stay the same"...

Many of these decisions are not done based on scientific methods, unfortunately.
Scientific method's speed is not the same as our current millisecond "goggle" era that we live in...