IAQ for Office Return

Ryan, If we can get pass the potential of liability issues, the fundamental is really the "equivalent outdoor air flow rate" (ASHRAE Epidemic Task Force).   While not necessary, it is a good place to be if there is more than or equal to .75 CFM/sf of "equivalent outdoor air" (outdoor air + the % of "clean" air coming through a MERV13 filter, 89% was used on the ASHRAE website) in a conventional office floor.  3 air changes of "equivalent outdoor air flow rate" can eliminate 95% of contaminants indoor. In Canada, there are a few companies claimed they can detect SARS-coV2 in the air, but many are wondering whether that can be done in real time.   Others use CO2 and PM 2.5, while related, they are not very good proxy. The air quality indicator maybe more about general wellness, which is more helpful and different certificates have different parameters, mostly CO2, CO, PM 2.5, VOC, Formaldehype, NO2, SO2, Ozone, some has Radon, Lead etc. The among of outbreaks in offices are low, there are more outbreaks in homes, entertainment venues etc.  Many are ok not wearing mask in a bar, restaurant, or home, but worry going to an office where most people wearing mask?  

Ryan - I'd just add on to what Luke said because I'm in agreement. We look at air quality monitoring as one of the final strategies (but an important one) that comes after we've done the other fundamental things like assessing the mechanical system performance, modeling different scenarios through our Facility Infection Risk Estimator tool (on our website if you need it) and then establishing different behavioral requirements. The IAQ monitoring component is a lot about making sure that the mechanical system continues to run as expected, and we would likely see issues reflected in the IAQ results, particularly CO2. So while it's not a perfect proxy, we're targeting 600-800 ppm, and if we saw big spikes in that we might find out that there's an HVAC issue or system limitation, say in perhaps a conference room. So we've also got portable HEPA filters deployed in some of those areas. We're in a combination of buildings we own and large multi-tenant buildings where we're dependent on a landlord running the building well... so we trust but verify.  We've used some different sensors and platforms, and generally try to stick to RESET accredited monitors. We're bringing Kaiterra Sensedge Minis online in all our offices into a separate data platform, so I can't really attest to their API. But we've used some other brands as well and I've still got some Airthinx devices going strong after three years. Airthinx hasn't done RESET accreditation yet for some reason - but it's nice that they have cell cards in them that allows them to not be reliant on a local network. That was helpful this last year when we let them get borrowed by a school district and didn't have to worry about network integration. The downside is that their SAAS model is a bit steep in my opinion ($300/yr per device), probably to cover the cellular data costs.  I'm sure Sarah Gudeman from our SMEP Peer Network has some good advice as well. She's done some Youtube reviews on different devices. 

Thanks for the insight. I think I understand your approach from a MEP design perspective , however I'm not sure I fully understand why additional montioring of CO2 levels would not be a good proxy for existing systems, presuming that the systems allow for higher CO2 levels to call for more fresh air delievery. Monitoring the outcome would be more critical than monitoring the input, no? Incidentally, I found the referenced video and put the link here. IAQ Monitoring for Virus Mitigation https://youtu.be/H-1EQz5a9Y4 "Interest in Indoor Air Quality (IAQ) is picking up steam in the wake of the coronavirus pandemic of 2020. In this video, Sarah Gudeman talks though the 5 parameters that continuous monitors generally track to gauge 'good' indoor air quality and how they relate to virus mitigation strategies."

Conor - that might have been a question for Luke, but personally I don't think CO2 is a bad proxy, just not a perfect one. In the case of a system with demand control ventilation, what you described is accurate in terms of the desired control. One of the reasons people caution using CO2 as a proxy is that the same CO2 levels in two different spaces could be incredibly different from a safety standpoint. Most filters don't do anything about CO2, so you can have a space with really well-filtered air and high CO2 be pretty safe when looking at viral load. (Though it's probably not great for cognitive function...).  There are loads of schools with systemic ventilation problems for example, and if the whole system isn't being addressed, then the primary recommendation from the research community is to install portable HEPA filters. So there's a case where the CO2 is probably not going to be a very good proxy for the viral conditions in a space unless you are taking that into account. So 1,200 ppm of CO2 in a classroom with HEPA filtration is far safer than 1,200 ppm in one without. I think this group would understand that nuance, but there are a lot of people out just want one metric to assess safety, and unfortunately it's not that easy. 

Hello: In our new office TI in Oakland California SERA installed RESET monitors and is certified under the RESET protocol. We also participated in the RESET Materials beta that is now available. We are looking forward to monitoring the performance of the space when it is occupied soon. The design of the space includes Big Ass fans for mixing and thermal comfort as well as operable windows. We chose RESET because it is a "standard" rather than simply deploying monitors at peoples desks in random ways. The system that we installed (pre-COVID) allows us to compare the quality of fresh outdoor air to filtered recirculated air. This will help us understand if the operable windows are the best air. RESET (and others) have been doing some work to understand how the sensors can understand virus loading potential. This is another feature that we look forward to using when we occupy. Compromised outdoor air from California wildfire and particulate concentration from the urban environment of Oakland were at the forefront of our thinking in the design. Obviously, now we need to weigh the quality of outdoor air, filtered outdoor air and filtered recirculated air, or combinations of the above, in the different occupancies of the office. The outdoor air sensors we chose also allow us to participate in the Plant A Sensor program to better understand the air quality in urban environments.     Best, Dave

Thanks Pete. I hear what you are saying now. but from a practical POV for an existing building and system, if you're getting CO2 ppm down to 600-800 you'd likely be diluting any viral load and other contaminants (and exhausting them) even if you're not capturing it.  obviously both filtering it out and delivering fresh air is the ideal case and i'm presuming that building filtration is being correctly maintained. maybe that is a bad presumption. ;)

Thanks again for the insights.

Team, Like the discussion!  Agreed with Pete.   CO2 has been under much discussion as a proxy for both normal and emergency times. Clean air under COVID-19 does not has to come from outside (i.e. the "Equivalent" outdoor air approach).  So with HEPA, or, MERV-13 (89% on one pass per ASHRAE), you can get "clean" air after multiple passes on the filter, but CO2 level can be around 1000 ppm. There may be multiple people in the room infected, if fresh air is enough, CO2 PPM will be good, but the material count in the air can be high, especially if recirculation is not going through MERV-13 filter minimum properly.  CO2 correlates better to outside air and number of people in the space, not directly to SARS-coV2 material in the air.    

Luke, Pete, Conor, et al. Great discussion and some excellent points already raised here. This is not my area of expertise, but my best friend is a professor of applied mathematics at MIT, specializing in fluid dynamics. He and a colleague have been working on modeling airflow, ventilation rates, spatial volume, activity, and most importantly time, as a way to plot risk. I'll upload the paper, but caution that it is very dense and much of it tends to be deep into the math behind the risk assessment. They do recommend using CO2 as the easiest proxy. Links below to an article that provides a brief overview, and the app that they devleoped to allow people to plug in parameters to determine risk guidelines. https://indoor-covid-safety.herokuapp.com/ https://scitechdaily.com/mit-develops-a-method-to-assess-covid-19-transmission-risks-indoors/

Great stuff all around. Interesting to read about OA introduction also not being the ideal in some locations beacuse of OA quality concerns. I'm curious about responses to Ryan's original question...How to translate all this nerd-speak (term of endearment!) into accuate, meaningful and displayable metrics for the building occupants / employees returning the office? :) What we need to do to address the concern may be different from how we present the information to the general public. All introduced air is 100% HEPA filtered and CO2 is maintained at cognitive functioning levels? 

Coming late to this thread but excited to weigh in on the nerd-speak.

Agree that RESET listed IAQ monitors are a good starting point, the ‘big 5’ parameters people usually tend to measure are temperature, RH, CO2, TVOC, and PM (usually 2.5). https://www.reset.build/directory/monitors (Note that not all RESET accredited monitors include all five of these parameters though). Kaiterra and Awair both have great solutions for monitors and display capability for lobby dashboards. Stay tuned for some useful comparison documents on IAQ sensors coming out of our IAQ working group too. https://www.buildinggreen.com/peer-networks/indoor-air-quality COVID-specific monitors focus on measuring for things like ozone and/or formaldehyde (or even ions in the space or at HVAC equipment discharge) too if ionization is being considered... CO2 is, I think, a good proxy measurement for ventilation performance IF the spaces are fully occupied and ventilation systems are operating per design intent. Not to mention, CO2 setpoints as described in ASTM D6245-18 are really just an indicator of body odor acceptability. I know Luke could talk more on this. “… the same level of body odor acceptability was found to occur at a CO2 concentration that is about 650 ppm above the outdoor concentration.” So really, it all gets back to body odor. Not viruses, not organic contaminants, not particulates. We have some more work to do here for sure. But remember that ventilation is just one of our ‘layers of protection’ (combined with masking, distancing, scheduling, etc). As shown in BranchPattern’s calculator, there are a lot of other parameters to be considered before we can talk about effectively mitigating risk. https://branchpattern.com/research/facility-infection-risk-estimator/

When it comes to IAQ / HVAC and virus mitigation, I think most of us agree the prioritization is something like:

1. Ventilate with outdoor air – hvac system or windows
2. Increase filter efficiency to ≥ MERV-13
3. Supplement with air cleaners
4. Monitor IAQ and verify performance

Sarah, as always, well and cogently stated.  I would however like to quibble with your prioritization of measures. I wish this thing would let me embed an image. Go to Google Images and put "Azimi and Stephens Building and Environment" in the Search box.  When you do, I hope that you see a very ugly graph that has infection risk on the vertical axis and annual cost on the horizontal.  In the body of the graph will be a squiggly L shaped line on the left side with about half a dozen nodes on it.  To that right of that squiggly L will be four swoopy lines. The story that this graph tells is that filtration beats the heck out of greater outside air.  And that you don't need to go past MERV 13.   BIG FOOTNOTE:  This study was funded in part by the National Air Filtration Association (NAFA) Foundation.  Makes me wonder what conclusions we would see from a study funded in part by the National Fresh Air Foundation [if such an organization exists]…

I am not a fan of treating ventilation and filtration as equivalent ("clean air changes") or as competing IAQ strategies.  Filtration removes airborne particulates from the both indoor and outdoor sources.  Ventilation exhanges indoor air with outdoor air.  Any good HVAC system does both, and no one should accept an HVAC solution that does not provide both appropriate ventilation and appropriate filtration. I agree that for most general applications MERV-13 filtration is appropriate.  But MERV-13 filters will not remove gasses (VOCs, CO2, ozone, odors) or very fine airborne particulates.  Excess ventilation is an energy or IAQ concern if ambient thermal or humidity conditions are extreme or ambient IAQ is poor.  But even in relatively extreme climates there are extensive hours (at night, during shoulder seasons) where excess ventilation does not cause excess heating and cooling loads.  In areas with really poor ambient air quality, you have to address that. . . but still I would rather err on the side of a bit too much ventilation air than not enough. PM2.5 is a decent proxy for filtration performance.  CO2 is good proxy for ventilation performance in occupied spaces.  Viruses are exhaled by infected people. . . so if you want to track just one IAQ number to assess COVID risk, CO2 would be my choice. 

Kim - I'm trying to upload a PDF of that graphic for you. It is a little blurry after my copy, paste, enlarge. Hopefully the attachment works. One thing I wish the image also showed is dots corresponding to the different outdoor air ACH levels, similar to the MERV level dots.  

Sarah - I'm looking to clarify the "CO2 concentration that is about 650 ppm above the outdoor concentration" line in your post. If outdoor levels are currently 415 - 420 ppm, then the corresponding indoor setpoint would be 1065 - 1070 ppm for CO2? Is that correct?  Makes me think of the 2015 Harvard School of Public Health (HSPH) study where CO2 levels at 945 ppm corresonded to a 15% reduction in congnitive function. ASHRAE 62.1 puts 1100 ppm as the threshold between adequate air quality and poor. That just seems to be too a high number. As you suggested, a better level is needed for interior CO2 levels that is health focused. 

I like the prioritization list you shared Sarah. Harvard School of Publich Health has finally created a graphic to communicate those priorities. Hopefully, that attachement works too. More good info and links at: https://schools.forhealth.org/risk-reduction-strategies-for-reopening-schools/healthy-buildings/  

Here is a link to one more, very short, IAQ / virus article that came out last month. It calls for setting a number instead of just provide more outdoor air, which potentially led to HSPH publishing a 5 or 6 ACH recommendation for schools and the info graphic. https://jamanetwork.com/journals/jama/fullarticle/2779062 

I'm curious if the combination of high filtration levels on portable air cleaners, or even recirculated mechancial systems, with high filtration levels on outdoor air delivery if that could mean a slight reduction in the Harvard recommendation of 5 or 6 ACH down to a 4 or 5 ACH level and still have the same IAQ effectiveness. Thanks,
Mike

There are studies support high level of filtration (MERV-13) minimum plus outdoor air to achieve "equivalent" clean air of about .75 CFM a sf, or, about 5 air changes per hours in a 9' ceiling office, is a good number to minimize risk.   This "equivalent" is for SARS-coV2, not other air borne material. There are inconsistency regarding research in CO2 conentration and cognitive performances.  NIST is penning a statement, but it has been delayed.   It should be coming out soon. Best, LL

Curious to see what the thought is on how (or if) germicidal UV enters into the equation. My understanding is that it’s the equivalent of far higher ACH when used in conjunction with MERV-13, etc Sent from my iPhone Roger Capestany-Gonzalez Project Manager Mobile: 206-940-2327 | Main: 206-682-3030 | Fax: 206-682-6627 Roger.Capestany@schuchart.com www.schuchart.com [cid:imagecf9bb7.GIF@878020fc.46b2980a] ___________________________________________________________________ Schuchart ● 919 5th Avenue ● Seattle ● WA ● 98164 The information transmitted, including attachments, is intended only for the person(s) or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and destroy any copies of this information. On May 11,

Erik is right on and I agree that these strategies aren't necessarily comparative. I was presenting in terms of prioritization for "things to do" specifically to address the COVID-19 response. (Though Kim you're right that generally for this purpose we wouldn't recommend going above MERV 13). I was definitely cribbing from the Harvard School of Public Health - thanks Mike for that link. I also think that "ventilation > filtration" is intended to ensure that existing systems are functional - without economize failures and the like. It all depends on ambient air quality too of course! 

Feels like people get caught up in strategies and assume since the treatments are similar they all end up in the same result ("good air quality"). But as others have stated, what type of result we're trying to get to depends on the treatment... or vice versa. And I think we as an industry are still grappling with what "good air quality" means - to Luke's point. 
  So, Roger, I'd say the follow up question is related to what you're trying to achieve. Assuming we can't do "everything" on a project these are the kinds of cost / benefit conversations that often come up. Code minimum ventilation, increased outdoor air, filtration and what level, activated carbon or gaseous filtration, UVGI, other air cleaner things, air quality monitoring and control (ASHRAE IAQP), etc (not to mention humidification)... all depends on goals and budget, right?   

Following up on the "which one is best" theme that seems to have developed here, I'd make another shameless plug for the tool we created, which was developed precisely to help with those types of decisions. It's free and we didn't even stick any tracking in it that we could then use to target you with ads for filters, so hopefully another link to it will be OK. 

https://branchpattern.com/research/facility-infection-risk-estimator/

A lot of the discussion is pretty model-able*. I've spent enough time in it that my usual response to "which one is best" is a big "it depends." It depends on what you're starting with for baseline conditions and how far you take it in your design case. The inability to give a one size fits all suggestion ought to make energy modelers feel right at home in it. 


Footnote:
*We're only looking at this through the lens of viral infection, which is a pretty obvious component of what makes for "good IAQ." Cognitive function might be a different lens to look through, in which case CO2 is probably an important input. But in the spirit of the original post, I think that in an "IAQ for Office Return", viral transmission is going to be the dominant theme.