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AirGradient Forum

High outdoor NOx values

#1

I’ve been noticing high NOx values that I don’t remember seeing before. Maybe a bug in my software, but I’m not so sure. In the graph below, the yellow line is the Open Air NOx index which spikes overnight in this case.

I have a high efficiency natural gas furnace, but the exhaust is on the right side of the house from where this sensor is located, so I would be surprised if it was drifting that far, and doesn’t seem to correlate to the runtimes of my furnace since it went idle overnight between 10:00 pm and 4:30 am

Any thoughts as to possible causes?

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#2

Could it be fireworks or bonfires in your area? My PM outside was really bad at midnight…

#3

Good thought. I did see it last night as well, but could be some Pre-New Years celebrating then too. I did see some short spikes over the last week, but not as sustained as the graph I showed.

If this was PM2.5, I would for sure think fireworks, but wouldn’t have expected NOx to be related to that as well. I don’t think I’ve ever seen NOx change in my home from 1, so surprising to see it get so high outside. Was wondering if a gas leak could show that, but I’m thinking it is only related to combustion and not the presence of natural gas?