# A simple question about PM25 in 2017gb..monthly..report
**URL:** https://forum.cmascenter.org/t/a-simple-question-about-pm25-in-2017gb-monthly-report/2924
**Category:** Emissions Inventory
**Created:** [December 23, 2021, 2:45am UTC](https://forum.cmascenter.org/t/a-simple-question-about-pm25-in-2017gb-monthly-report/2924 "2021-12-23T02:45:57Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Rypo](https://forum.cmascenter.org/u/Rypo)
#### Post date: [December 23, 2021, 2:45am UTC](https://forum.cmascenter.org/t/a-simple-question-about-pm25-in-2017gb-monthly-report/2924/1 "2021-12-23T02:45:57Z")
Hello,
I just want to make sure a simple thing that PM25 emission contains PEC and POC and its unit should be short tons in the file “2017gb\_hapcap\_county\_monthly\_report\_CAPs\_PEC\_POC\_09apr2021.xlsx”, right?
Thank you in advance.
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### Author:  [@eyth.alison](https://forum.cmascenter.org/u/eyth.alison)
#### Post date: [December 23, 2021, 1:26pm UTC](https://forum.cmascenter.org/t/a-simple-question-about-pm25-in-2017gb-monthly-report/2924/2 "2021-12-23T13:26:45Z")
Yes, all of the units are short tons.
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### Author:  [@Rypo](https://forum.cmascenter.org/u/Rypo)
#### Post date: [December 23, 2021, 2:18pm UTC](https://forum.cmascenter.org/t/a-simple-question-about-pm25-in-2017gb-monthly-report/2924/3 "2021-12-23T14:18:05Z")
Thank you, happy holiday!
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### Author:  [@Rypo](https://forum.cmascenter.org/u/Rypo)
#### Post date: [December 23, 2021, 6:56pm UTC](https://forum.cmascenter.org/t/a-simple-question-about-pm25-in-2017gb-monthly-report/2924/4 "2021-12-23T18:56:46Z")
Hi Alison,
Sorry, two more simple questions.
I am trying to further QA my generated emission. I tried to convert NO and NO2 in my emission files (mol km-2 hr) to NOx (short tons), but it looks underestimate 30% relative to NOx in that EPA’s report. I found that “For all source categories, NOx is compiled from emissions measurements that express NOx mass based on the molecular weight of nitrogen dioxide (NO2), which is 46” in [https://www.epa.gov/air-emissions-inventories/how-are-oxides-nitrogen-nox-defined-nei](https://www.epa.gov/air-emissions-inventories/how-are-oxides-nitrogen-nox-defined-nei)
So I should use 46 molecular weight for converting NO to tons, right?
For mobile source, what’s the relationship between HONO and NOx?
Thank you.
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### Author:  [@eyth.alison](https://forum.cmascenter.org/u/eyth.alison)
#### Post date: [December 23, 2021, 7:18pm UTC](https://forum.cmascenter.org/t/a-simple-question-about-pm25-in-2017gb-monthly-report/2924/5 "2021-12-23T19:18:58Z")
Yes, I think you are right about the MW to use being that of NO2. HONO is usually 0.8% of the mobile sources.
More information is in the speciation section of our TSDs. For example there is one linked from here:
[https://www.epa.gov/air-emissions-modeling/2016v1-platform](https://www.epa.gov/air-emissions-modeling/2016v1-platform)
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### Author:  [@Rypo](https://forum.cmascenter.org/u/Rypo)
#### Post date: [December 23, 2021, 7:37pm UTC](https://forum.cmascenter.org/t/a-simple-question-about-pm25-in-2017gb-monthly-report/2924/6 "2021-12-23T19:37:38Z")
I see, thank you for your speedy reply!