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Measuring IAQ

Measuring IAQ

Measuring IAQ

(OP)
Presently I am running a lot of tests seeing how effective ventilation is, how well positive pressure helps me control humidity here in the tropics. Humidity control has been excellent, now I am focusing on the level of CO2.

I had an intermittent residential ventilation strategy for cold winters, trying to work out something other than steady fresh air and humdity pumped into a tropical home right now. Commercial/industrial spaces you pretty much always have a cold coil here so is a lot simpler to ventilate continuously.

I found an interesting thread here, with quark giving some very good info.

http://www.eng-tips.com/viewthread.cfm?qid=163576

thread403-163576: Ventilation Rates - ASHRAE 62-2004

Quote:

quark (Mechanical) 26 Aug 06 4:45  
I am comfortable with 15 to 16 cfm/person and generally go higher in special cases. Fundamentals of Refrigeration and Air Conditioning by Shan K Wang gives a plausible calculation for the fresh air rate.

The atmospheric air contains about 300 ppm (0.03%)of CO2 (and upto 600 ppm).

a medium sized person with normal health produces about 0.0116cfm of CO2

If we have to limit the indoor concentration below 1000 ppm (or 0.1%),

The fresh air requirement is 0.0116*100/(0.1-0.03) = 16.57 cfm/person

For healthy adults, the threshold limit for 8hrs is 5000 ppm. In this case, the fresh air rate may be 2.5 cfm/person. This may be the reason for low fresh air rates given in the standard.

I recently purchased a CO2 meter that can be logged by a HOBO with external channels. Brand new out of the box. Finding my ambient CO2 at home about 440 PPM in what could be thought of as a wind swept suburban area on an isolated island without major industry. By my office with a fair bit of traffic it was around 470 PPM. Meter says it is accurate to 50 PPM.

I could just imagine what the CO2 is like during traffic grid lock in a major industrial city. So following the Shan Wang rationialization, and using higher values than 300 PPM, could mean a lot more air per person.

I also surfed around and found this http://cdiac.esd.ornl.gov/trends/co2/contents.htm

All these remote Island stations, Arctic Staions are recording 370 to 380 PPM. Being remote they are free of perhaps, influences of traffic and industry, maybe also being isolated Islands and arctic areas, it is not like they are benefitting from forests and plants but must be some algae/coral sucking CO2 out of the air except in Alert.

So I have seen atmospheric CO2 written as low as 300 in other references, I am wondering if the reference is perhaps old, as in a couple decades of emissions earlier?

I just downloaded both of the 2007 ASHRAE 62's and I am in the positon to play around with a lot of rates to see some results.

You get on sites with all the industrial hygenists and they are calibrating their portable CO2 meters and going into buildings and comparing their readings to the CO2 sensors used to step up the ventilation and are finding a lot of error in the building sensors.

Anyone in their checking CO2 levels in buildings they designed, measuring ambient CO2?

Take the "V" out of HVAC and you are left with a HAC(k) job.

RE: Measuring IAQ

Modtran, which is an Air Force developed atmospheric transmission model, lists CO as traditionally, 330 ppmv, although it says in the manual that the more current (1999) value is more like 365 ppmv, based on some unpublished data from NOAA.  

Your cited site's data seem to all show a general increase of about >40 ppm over the last 40 years

TTFN

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