[puzzledarchitect]

I am recording VOCs emitted in a painted room using a Wolfsense IQ-604 probe (uses PID technology). As expected, VOC levels increase when the windows/doors were closed in the room but in the morning they dropped as you will see in the graph:

http://i.imgur.com/0exn2pO.png

The room was vacated/undisturbed at this time. The TVOC drop occurred after sunrise and the room gets direct sunlight for a short time in the morning so I suspect photochemical reactions are the culprit.

Can anyone offer some suggestions as to what has happened? Google has revealed VOCs react with NO2 to produce ozone but I can't find anything that talks about VOC reformation (the VOC level in the graph returns back to it's peak).

(I am an architect not a chemist so this is new territory to me)

[Arkcon]

Thank you for posting this, I'm grateful for all the technical info.  Usually, we just get I bought low voc and it still smells,what wrong.  So this is a very good posting.
Problem is, I can't really help, because I dont know the specifics of how this analytical instrument works.  However, the photoconversion reaction shouldn't happen based on a few hours of sunlight, through a window, unless this is some sort if greenhouse.  I suppose there could B son sort if hidden ventilation system, but you of all people should be aware of that.  Without understanding the detector more thoroughly, we can't B sure Thu its own variability.  Maybe you should share you results with the vendor.

[DrCMS]

What was the room temperature over the same time period.  What else is in the room?  Is this just adsorption/desorption equilibrium changing with temperature?

[P]

maybe the 2 or 3 hours of sunlight drove of the remaining VOCs and now they have just dissipated out of the room.