High indoor VOC counts

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neb

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#214957 5-Jun-2017 18:49

I've got an environment sensor on the house that monitors humidity, particulates, VOCs, and so on. I've been getting high, sometimes alarmingly so (700ppb), VOC readings that climb rapidly around 4-5pm, seem to peak mid to late evening, and then gradually decay again through the night. There's no obvious cause (cooking, outdoor activity, etc), and sometimes the spikes come late in the afternoon rather than evening.

Any ideas what it could be? I can provide more details on all the things that aren't causing it if people have specific questions.

solutionz

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#1795014 5-Jun-2017 18:55

UV?

gzt

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#1795015 5-Jun-2017 18:58

Sensor just installed?

vs installed for a long time, stable readings, and now this.

neb

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#1795016 5-Jun-2017 18:58

solutionz: UV?

How would UV affect VOC counts, and why at night when there's no UV? That's meant as a serious question, it could well be something like that but I can't see how it would specifically be UV.

I've got LED lighting in the house but it's probably not that because the counts decrease over time when, with prolonged LED light exposure, you'd expect them to increase of that was the cause.

neb

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#1795017 5-Jun-2017 19:00

gzt: Sensor just installed?

vs installed for a long time, stable readings, and now this.

Had it for about a year. I never noticed the spikes until a month or two back.

And to anticipate the obvious question, there's nothing that changed a month or two back that I can think of. I thought it might be a new couch outgassing solvents, but you'd expect that to be worse during the day with warmer temps.

solutionz

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#1795019 5-Jun-2017 19:05

neb:
solutionz: UV?

How would UV affect VOC counts, and why at night when there's no UV?

If your room is located and situated as such that it begins receiving the direct afternoon sun; and the UV is causing furnishings in said room to off gass it could account for such a situation (begins to raise 4-5pm and drops off in evening).

neb:
And to anticipate the obvious question, there's nothing that changed a month or two back that I can think of. I thought it might be a new couch outgassing solvents, but you'd expect that to be worse during the day with warmer temps.

Azimuth is changing factor..

Assuming you've accounted for other human-related factors like sitting on the couch potentially releasing extra VOCs, appliances etc..

richms

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#1795020 5-Jun-2017 19:07

New shoes? I have some that outgas something massive and could be because they are sitting near the sensor

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neb

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#1795027 5-Jun-2017 19:21

JP:
If your room is located and situated as such that it begins receiving the direct afternoon sun; and the UV is causing furnishings in said room to off gass it could account for such a situation (begins to raise 4-5pm and drops off in evening).

Ah, of course! So that's now made it the most plausible explanation, the room does indeed get direct sun after about 2pm, finishing about 5pm at the moment, and there were a few temperature peaks that correspond to the VOC peaks which would indicate a lot of sun that day. The winter sun angle could be the reason why it's appeared in the last month or two. It's also easily tested, I can keep the curtains (heavy blockouts) closed during the afternoon.

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Fred99

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#1796054 7-Jun-2017 17:16

What VOCs does the sensor detect?

Big difference IMO between a constant near 1ppm if it's benzene or if it's methane.

What the outgassing is - could be anyone's guess - phthalates from vinyl, coalescing solvents (glycol ethers) in water-based paints, cleaning product residues etc, some relatively harmless - some perhaps cause for concern.

neb

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#1796061 7-Jun-2017 17:31

Fred99:
What VOCs does the sensor detect?

It'll be a cheap MEMS sensor rather than something like a photoionization detector so it doesn't specify, it's just "VOCs" ("It's chunky soup" / "What's in it?" / "Chunks").