[Bldg-sim] Acceptable CO2 levels

Julia Beabout juliabeabout at yahoo.com
Tue Feb 16 09:27:07 PST 2010


I thoroughly agree with Mr. Dirkes and have confronted the same situation Mr. Bonafe has described at contentious board meetings and public hearings over the years.  

I would just like to add a couple points to the conversation:

1. Under normal everyday levels and circumstances, CO2 is not a "contaminant" per se...as we all know, it is around us all the time and we breathe and exhale it constantly.....although, it doesn't help that the EPA has recently added to the confusion by classifying CO2 as a public/pollution hazard in order to try to regulate it from a climatological point of view.  Anyway, perhaps steering clear of using the word "contaminant" when discussing CO2 could help keep conversations with clients/the public productive.  

2. The other thing that does not seem to have been pointed out specifically, is that ASHRAE 62 recommendations are based on a differential level of CO2 with the outdoors.  It is the differential level between the indoor and outdoor levels of CO2 that is correlated with indoor air quality, not absolute levels of CO2 in the space.  Since most areas in the U.S. have an outdoor CO2 level of around 380 ppm, and a differential level of 400-500 ppm has been correlated with human perceptions of comfort for a given a given level of human activity and (in more recent editions of ASHRAE 62) the use of certain building materials, the recommended indoor levels are around 800 ppm.  So, the maximum levels of around 1000 ppm are  recommended not because CO2 is unhealthly above that level but because the greater differential with ambient levels of CO2 would correlate to lower amounts of outdoor air being brought into the building.  Studies have linked lower levels of
 outdoor air in a space to a reduction in human performance and perceptions of comfort.  So, perhaps focusing on the differential as the key to indoor air quality can reduce the fixation on a given level CO2 in a space. 



From: "James V Dirkes II, PE" <jvd2pe at tds.net>

To: "Bonafe, Wes" <wbonafe at moseleyarchitects.com>; bldg-sim at lists.onebuilding.org
Sent: Tue, February 16, 2010 11:26:48 AM
Subject: Re: [Bldg-sim] Acceptable CO2 levels

 
Dear Wes,
 
I think you are asking “How do I tell a non-technical client / customer that CO2 is not worth worrying about.”
 
First, it’s pretty hard to argue against popular opinion and the mainstream media’s  general inclination to promote gloom and doom.  After all, if ABC or MSNBC or the local newspaper or (fill in the blank) says it, it MUST be true.
 
My approach is something like:
·         Do my homework and become confident that I have a reasonable understanding of the basis for whatever position I take.
·         Be open to the (normal) reality that not everything is known about almost any topic.
·         Stand up for the truth and discourage worry or fear when it’s not warranted.
·         Present the best available information in a manner that helps non-technical people understand it.  In the case of CO2 or any indoor contaminant, it would be something like “The premier experts in the field of indoor air quality have condensed the requirements for acceptable indoor air quality into a single standard that is recognized throughout the world and updated regularly.  That standard is called ASHRAE Standard 62.1.  At Moseley Architects, we follow that Standard as well as other related standards and are confident that it represents the most current and comprehensive way to assure your health in an indoor environment.  Any questions?”
 
That still may not carry the day for certain of your clients, but what the heck!  Science is supposed to be a rational topic and you cannot argue an irrational objection; don’t try!
 
p.s., Since this is a building simulation forum, I should probably stop here.  Feel free to call or e-mail directly at jim at buildingperformanceteam.com. 
 
The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
 
From:bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Bonafe, Wes
Sent: Tuesday, February 16, 2010 10:53 AM
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Acceptable CO2 levels
 
Me again:
 
To me Mr. Dirkes’ seems well informed on the issue of CO2 concentration.  Our concern has been the public’s perception that one becomes sleepy, or drowsy when exposed to PPM levels of CO2 in excess of 1000 PPM.  As they say perception is reality and I can rarely come out on top of a discussion involving a concerned parent with “my opinion”.  Therefore the need for a study or printed information to reinforce “my opinion”.  We would considers a reference to the OSHA TLV, coupled with the 2000 PPM levels reached in a submarine.  Has the U.S. Navy printed anything?  Can I backup my opinion that high CO2 alone is a non-issue.  Mr. Dirkes’ comment was limited to CO2 and did not address all the other contaminants that can build up in a space.  There are products purported to eliminate these however they cannot eliminate CO2.  This requires that CO2 be allowed to increase in concentration above 1000 PPM within the space.  This, by the way, is easy
 (relatively cheap) to measure.  It appears there is no direct evidence “other than OSHA’s 5000 PPM TLV” that up to 5000 PPM CO2 causes no harm.  True?
 
As a disclaimer I have not read ASHRAE Standard 62.1.
 
Thanks for your assistance:
 
Wes
 
Wes Bonafe, P.E.
Chief Mechanical/Plumbing Engineer
Vice President
LEED Accredited Professional

MOSELEY ARCHITECTS 
Architecture. Engineering. Interiors. Planning
3200 Norfolk Street
Richmond, VA 23230
804.794.7555
FAX 804.355.5690
www.moseleyarchitects.com
www.moseleyprojects.com

Please consider the environment before printing this e-mail.
 
 
 
 
From:bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of James V Dirkes II, PE
Sent: Tuesday, February 16, 2010 9:18 AM
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Acceptable CO2 levels
 
Dear Bldg-Sim community,
 
A few more comments for your consideration:
 
ASHRAE Standard 62.1 is the principal reference used for acceptable indoor air quality.  It hasn’t been mentioned in this discussion, so I want to make sure you consult it.  It’s Appendix A says, 
“CO2 is a bioeffluent generated by people at a rate determined by their size, age, fitness, and activity level. At the same time people are generating CO2, they are also producing odorous bioeffluents. These odorous bioeffluents are generated proportionally to the rate of CO2 production, although diet and personal hygiene also play a role. Nevertheless, CO2 concentration is a fairly dependable indicator of the concentration of the odorous bioeffluents that the occupant component of the breathing zone ventilation rate attempts to control. Hence, we can use CO2 concentration to dynamically adjust the  occupant component of the ventilation rate to reduce outdoor air intake rates when zones are not occupied at their design occupancy.”
 
The key concept misunderstood in most discussions about CO2 is that maintaining a specific level of CO2 in an occupied space is done NOT because the CO2 is unhealthful, but because it’s a convenient indicator of occupant comfort.  Comfort in this case is measured by “odorous bioeffluents”, otherwise known as “body odor”.
 
While you can have harmful health effects from high levels of CO2, those levels are (essentially) never encountered in a building.  The only “real” situation I am aware of where CO2 concentrations exceed 2000ppm (which is less than 50% of OSHA’s TLV) is in a submarine; not too much fresh air available there!
 
I’ve paid very close attention to information about CO2 over the last 20 years or so because for many of those years, I worked for a  manufacturer of direct-fired heating equipment.  That type of heating is commonly used in industrial occupancies due to its exceptional efficiency (92%) and a few other factors.  One perceived downside of that equipment was that all of the combustion products, including CO2, are released into the occupied space, causing CO2 levels to rise, on occasion, to 2000ppm.
 
I also sat for several years on the ANSI Technical Advisory Group which wrote the current national standards for that equipment.  The member group of a couple dozen code officials, testing agency and manufacturing representatives conducted an extensive review of literature and found no evidence either in the literature or their collective experience that CO2 was a concern under 5000ppm.
 
In summary, my personal and fairly informed opinion is that the CO2 level in buildings is not even close to a health issue.  Follow ASHRAE Standard 62.1 and all will be well.  A recent post on this list referenced an article at buildingscience.com by Joe Lstiburek which (I think rightly) points out the huge energy implications of introducing more air than indicated by Std 62.1; that’s a bigger issue, I think.
 
p.s., I could not find any literature in my archives regarding a correlation between CO2 and drowsiness.  I don’t think there’s any literature indicating a strong correlation, certainly not at normal building concentrations.
 
The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
 
From:bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Bonafe, Wes
Sent: Tuesday, February 16, 2010 8:29 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Acceptable CO2 levels
 
All:
 
Thanks to Mr. Dirkes.
 
Can anyone direct us to a study that says high CO2 in and of itself does not cause health issues especially drowsiness?  We have asked for such a study from those providing filtration prior to considering such filtration on our projects.
 
I think CO2 is definitely related to energy use/modeling because you can reduce levels of outside air if allowing higher CO2 levels.
 
Thanks:
 
Wes
 
From:bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of James V Dirkes II, PE
Sent: Monday, February 15, 2010 4:39 PM
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Acceptable CO2 levels
 
Dear Amit,
 
Keep in mind that ASHRAE’s “acceptable” level of CO2 has almost nothing to do with health.  You could describe it as more of a “body odor” or “pleasantness” index.  When the ambient levels of CO2 exceed their recommendation (~1000 ppm), people start to feel that the indoor air is less pleasant or “stuffy”.
 
Health does not start to be affected until CO2 exceeds 5000 ppm. (per US EPA and ACGIH)
 
The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
 
From:bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of amitbhansali
Sent: Monday, February 15, 2010 4:24 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Acceptable CO2 levels
 
Hi all,
This question is not directly related to the group but i wanted to  throw it in as many of you might know the answer.
 
What is the acceptable CO2 level for a healthcare facility? Can i find the number in any ASHRAE standards?

-- 
Thanks

Sincerely,
AmitBhansali, M.S. , EIT
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