PAC Database - Detailed Chemical Data

Chemical Identity
Chemical CAS# UN# Health Code Numbers
Nitrous acid 7782-77-6
3.08
3.06
Formula Synonyms
HNO2
Physical Properties
Mol Wt State MP (°C) BP (°C) VP (Hg) VP (°C) SG LEL (ppm)
47.01 L
PAC Values
PAC Values (Original Units: ppm)
PAC-1 PAC-2 PAC-3
0.16 24 92
Converted PAC Values (mg/m3)
PAC-1 PAC-2 PAC-3
0.31 46 180
Technical Basis
Nitrous acid is a product of combustion when nitrogen dioxide reacts with water; it only exists in solution. A review of available sources identified no exposure limits or acute toxicity data for this chemical. A review of available sources identified AEGLs for similar chemicals, Nitrogen dioxide (CASRN: 10102-44-0) and Nitric Acid (CASRN: 7697-37-2); of these, nitric acid reports more conservative exposure limits. Considering this, the AEGLs for nitric acid were selected due to their priority among Protective Action Criteria (Section 1).
• PAC-1 = AEGL-1 (Nitric Acid, CASRN: 7697-37-2)
• PAC-2 = AEGL-2 (Nitric Acid, CASRN: 7697-37-2)
• PAC-3 = AEGL-3 (Nitric Acid, CASRN: 7697-37-2)
This review generated PAC values inconsistent with Rev. 29A. The Rev. 29A and current PAC source are consistent; however, Rev. 29A applied a molecular weight adjustment to published AEGLs (ppm). Instead, the current PACs (ppm) are reported without adjustment, according to Section 3.2.2.
References
Chemical information retrieved from: https://pubchem.ncbi.nlm.nih.gov/compound/Nitrous-Acid
AEGLs for nitric acid (CASRN: 7697-37-2) retrieved from: https://www.epa.gov/aegl/nitric-acid-results-aegl-program
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PAC values marked with a subscript "A" correspond to 60-minute AEGL values.
PAC values marked with a subscript "E" correspond to ERPG values.
PAC values marked by * are >= 10% lower explosive limit (LEL) but < 50% LEL.
PAC values marked by ** are > 50% LEL but < 100% LEL.
PAC values marked by *** are >= LEL.