[Bldg-sim] Acceptable CO2 levels

[James V Dirkes II, PE]

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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