[UPDATED: Added video] Gas sickness (CO Symptoms) but not from natural gas?

During my morning inspection yesterday I started to feel light headed, dizzy and foggy. I test the house for CO (zero), so I thought it might be formaldehyde from the flooring. But that was not it: according to the flooring labeling. Then I remembered that I started to feel strange after coming out of the attic (20+ minutes up there checking out the running furnace and small attic space). The real estate agent and buyer both were not affected while in the house. I left to do my afternoon inspection but returned (feeling 95% better) to check the CO levels in the attic and garage (in case the WH & furnace flues were leaking)…All zero CO but I had the symptoms of CO. Then I tested with my combustion gas monitor and it detected something (performed the test 3 times with the same results), no smell of gas though. The gas company paid a visit but said there was no gas detected (so they say).

Any ideas?

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Sounds like symptoms of vertigo.


I am a rock climber :slight_smile: It is why I live in the this mountain town: the limestone walls are amazing! So, that is unlikely since it took 4 hours to mostly go away. Thank you anyway!

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Did you re-experience the dizziness on your revisit to the attic? If not, maybe some sort of one-off thing. It takes very high CO levels to affect you in 20 minutes. I’ve been in 100 ppm for 30 minutes with no symptoms, though that level had made the tenant very ill. So, if not a one-off bad morning, then maybe a mild allergic reaction to some dust you stirred up.


Yes, I felt a little on the revisit.

Hey Bill,
Sorry to read of your recent experience. its a good reminder to us all about the potential dangers we face at some properties.
I hope someone has a good explanation for you.

I’m stumped by the lack of an odor for a chemical or gas that would cause dizziness. Besides CO or Propane or Natural gas leaks there could be sewer gas leaks but CO is the only one on that list with no odor associated, and you already tested for that.
I hope another member knows of a substance in the attic that might be the culprit.


In my opinion, you shouldn’t necessarily rule out slight vertigo, especially if there are no other indicators of what might be the cause.

Vertigo is fairly common and can take awhile to dissipate. It is an inner ear affliction so has nothing to do with your location (mountains) or the fact you are a rock climber.

Sometimes this can be a mind trick, lol.


It could be a lot of things that caused it. None of us are doctors. It also has nothing to do with your physical health or your activities.

A friend of mine would get the same symptoms at different times throughout the day, almost every day at work. They had the fire department come in and run tests on multiple days and they could not find anything. The doctor told him to keep a log of his activities. What they found out was that the harmonics of a motor vibrated the floor just enough to cause it. For whatever reason, he is the only one affected by it. The same thing could have happened to you with the blower motor on the furnace.


Kind and considerate words! Thank you!

Thank you!
There seems to be a focus on health and not the gas detector, which detected something 3 times. Each time I started from the outside of the house after auto-calibration, slowly walked inside towards the garage. While in the garage I walked around and then pointed the gas detector in the attic hatch. Each of the 3 times that is when the detector went fill tilt. I took a video of the gas test but it was too large to upload. Just now edited it so it fits under 100mb, the last 5 seconds is the alert. I will see if I can add it to the main comment above.


Jeff, I agree with you on the motor harmonics. I have experienced this. Would this also impact the reading on a gas sensor?

Another option for large videos if you have a youtube acct is to load them up there and post a link here.


Do you have some pictures of the attic interior? Maybe someone will see something suspicious.


To begin with… you need to use the proper test equipment for the job.
The Klein ET120 does NOT test for CO or other NON-combustible gasses!
Klein states it only tests for Methane, Propane, Butane, as low as 50 PPM.


Here is everything from the attic and attic


Agreed, I first tested with a Fieldpiece SCM4 CO tester (see picture I posted to Ryan’s idea). In any case, the monitor I did use for the gas found something…would you agree with that?

False positives and negatives are always possible, with both pieces of equipment.

Also, there appears to be good ventilation in the attic.

But, the furnace is at 15 years so heat exchanger issues are always possible. And I am curious what others think about the quality of this flame.



Can’t tell from a picture. No blowout. Heat exchanger problems don’t show till the blower comes on.


Now that you brought that up, there is another question. Is there enough makeup air in the attic?

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Thanks Brian! I appreciate it!