In a message dated 97-03-07 10:47:01 EST,
d (Andrew Persily) writes:
> A few comments; do with them what you will.
> First, EPA has no requirement for
> indoor CO2 levels, not 1000 not 800 not nothing.
> I also disagree with the first statement about CO2
> being the most accurate means. It is only true if you
> are only ventilating for "people-based" sources, that is,
> contaminant sources that depend on the number of
> people. While many codes and standards are in
> the form of cfm/person, there are many sources that
> are independent of the number of people in a space or
> building. For example, floor coverings and outdoor
> pollutants entering with the ventilation air. While
> CO2-based demand controlled ventilation has a lot of
> potential in some situations, important
> questions remain on when and how to use it and what
> it gets you. A literature review on the subject will be
> presented at the ASHRAE meeting in Boston this
> June, authored by Steve Emmerich and myself.
>
> >
> > CO2 level is the most accurate means of controlling the need for
> > outside air.
> >
> > EPA requires level to be less than 1,000 ppm and I understand that
> > that may be dropped to 800 ppm very soon. If a fixed cfm/person is
> > used to bring in fresh air, the maximum amount of air will be
> > introduced weather the max or min amount of people are inside the
> > building. By monitoring CO2 levels inside and having C02 sensors
> > controll outdoor air dampers, the amount of fresh air will be introdced
> > in proportion to the internal ventilation demand.
> >
> > This is called demand controlled ventilation DCM, and is used
> > primarily with direct digital control DDC systems that are able
> > to accurately control dampers based on sensor signgals.
> >
> > Energy can be saved by only bringing in the amount of outdoor
> > air necessary at any particular time.
> >
>
>
> * * * * * * * * * * * * * * * * * * * * * * * * * * *
> * Andy Persily apersily@nist.gov *
> * National Institute of Standards and Technology *
> * Division 863 *
> * Building 226, Room A313 301 975-6418 *
> * Gaithersburg, MD 20899-0001 FAX 975-5433 *
> * * * * * * * * * * * * * * * * * * * * * * * * * * *
Andy is the chair of the ASTM E6.41 Subcommittee on Building
Infiltration that will meet in St Louis on 3/17-18. Standards that we
will be working on include backdrafting, radon mitigation, and blower
door testing. Let Andy know if you want to participate in any of these
task groups. We need input from folks with experience in these areas.
You can participate by mail.
I hope this is helpful,
....Dave Saum
Infiltec Air Leakage Control
www.infiltec.com
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