PAC Database - Detailed Chemical Data
Chemical Identity
| Chemical | CAS# | UN# | Health Code Numbers | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Nitrogen trioxide; (Dinitrogen trioxide) | 10544-73-7 | 2421 |
15.01
11.01
15.02
4.08
7.01
4.01
11.00
4.07
10.00
|
|||||||||
| Formula | Synonyms | |||||||||||
| N2O3 | NITROGEN TRIOXIDE, DINITROGEN TRIOXIDE, NITROGEN SESQUIOXIDE, NITROGEN TRIOXIDE (N2O3), NITROUS ANHYDRIDE, TRIÓXIDO DE NITRÓGENO (DOT SPANISH), TRIOXYDE D^AZOTE (DOT FRENCH) | |||||||||||
Physical Properties
| Mol Wt | State | MP (°C) | BP (°C) | VP (Hg) | VP (°C) | SG | LEL (ppm) |
|---|---|---|---|---|---|---|---|
| 76.011 | G | -101.1 | 1.4 @ 2°C |
PAC Values
| PAC-1 | PAC-2 | PAC-3 |
|---|---|---|
| 0.5 | 12 | 20 |
| PAC-1 | PAC-2 | PAC-3 |
|---|---|---|
| 1.6 | 37 | 62 |
Technical Basis
Nitrogen trioxide has a very low boiling point (3.5°C), indicating it will be a gas at conditions of standard pressure and temperature. Additionally, nitrogen trioxide “partially dissociates” to a mixture of nitric oxide (CASRN: 10102-43-9,) and nitrogen dioxide (CASRN: 10102-44-0)1; as such, available resources for nitric oxide, nitrogen dioxide, and nitrogen trioxide were reviewed.
As part of the chemical class of nitrogen oxides, nitric oxide, nitrogen dioxide, and nitrogen trioxide were evaluated in the National Research Council report: Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 112. In the report, nitrogen trioxide is not explicitly considered3. In lieu of such consideration, both nitric oxide and nitrogen dioxide are appropriate substitutes as they are expected byproducts of gas phase nitrogen trioxide dissociation.
The 60-minute AEGL-1, AEGL-2, and AEGL-3 values reported by the National Research Council for nitrogen dioxide are recommended to the nitrogen trioxide TEEL-1, TEEL-2, and TEEL-3 values. A compound adjustment factor was not used, per the guidance of the TEEL handbook4.
• TEEL-1 = AEGL-1 (60-minute; nitrogen dioxide, CASRN: 10102-44-0)
• TEEL-2 = AEGL-2 (60-minute; nitrogen dioxide, CASRN: 10102-44-0)
• TEEL-3 = AEGL-3 (60-minute; nitrogen dioxide, CASRN: 10102-44-0)
This review generated TEEL values are more conservative than those published in Rev. 29A due to a different basis.
As part of the chemical class of nitrogen oxides, nitric oxide, nitrogen dioxide, and nitrogen trioxide were evaluated in the National Research Council report: Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 112. In the report, nitrogen trioxide is not explicitly considered3. In lieu of such consideration, both nitric oxide and nitrogen dioxide are appropriate substitutes as they are expected byproducts of gas phase nitrogen trioxide dissociation.
The 60-minute AEGL-1, AEGL-2, and AEGL-3 values reported by the National Research Council for nitrogen dioxide are recommended to the nitrogen trioxide TEEL-1, TEEL-2, and TEEL-3 values. A compound adjustment factor was not used, per the guidance of the TEEL handbook4.
• TEEL-1 = AEGL-1 (60-minute; nitrogen dioxide, CASRN: 10102-44-0)
• TEEL-2 = AEGL-2 (60-minute; nitrogen dioxide, CASRN: 10102-44-0)
• TEEL-3 = AEGL-3 (60-minute; nitrogen dioxide, CASRN: 10102-44-0)
This review generated TEEL values are more conservative than those published in Rev. 29A due to a different basis.
References
https://cameochemicals.noaa.gov/chemical/4077
National Research Council. 2012. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 11. Washington, DC: The National Academies Press. https://doi.org/10.17226/13374. Retrieved from: https://www.epa.gov/sites/default/files/2015-09/documents/nitrogen_oxides_volume_11_1.pdf2
National Research Council. 2012. Pg. 173.
Section 3.2.2: “…the compound adjustment factors are applied to all exposure limits except AEGL...”