[Bldg-sim] Acceptable CO2 levels

Bonafe, Wes wbonafe at moseleyarchitects.com
Tue Feb 16 07:53:22 PST 2010


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 amit
bhansali
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,
Amit Bhansali, M.S. , EIT

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