{
 "license": "CC BY 4.0 — Tremon Solutions, https://www.tremon.nl/gases/so2",
 "generated": "2026-09-17",
 "key": "so2",
 "name": "Sulfur dioxide",
 "formula": "SO₂",
 "formula_plain": "O2S",
 "iupac": "sulfur dioxide",
 "synonyms": [
  "Sulfur oxide",
  "Sulfurous acid anhydride",
  "Sulfurous oxide"
 ],
 "cas": "7446-09-5",
 "ec_number": "231-195-2",
 "un_number": "1079",
 "un_shipping_name": "Sulphur dioxide",
 "transport_class": "2.3 (Toxic gases)",
 "pubchem_cid": 1119,
 "molar_mass_g_mol": 64.06,
 "mg_m3_per_ppm_20c": 2.66,
 "boiling_point_c": -10.0,
 "sublimation_point_c": null,
 "melting_point_c": -75.5,
 "critical_temp_c": 157.5,
 "critical_pressure_bar": 78.8,
 "vapour_pressure_bar": 3.3,
 "vapour_pressure_at_c": 20.0,
 "density_gas_kg_m3": 2.9285,
 "density_condition": "0 °C, 1013 mbar",
 "relative_density_air": 2.26,
 "solubility_water": "228,3 g/l at 0 °C",
 "appearance": "gas liquefied under pressure, colourless, pungent odour",
 "odour": "pungent odour",
 "chemical_character": [
  "Non-combustible gas.",
  "Soluble in water, hydrolyses.",
  "Forms sulfurous acid in water.",
  "Binds moisture from air and forms aerosoles!",
  "Aqueous solution reacts strongly acidic.",
  "Gas is heavier than air."
 ],
 "hazard_class": "toxic (corrosive, respiratory irritant)",
 "ghs_classification": [
  "Gases under pressure, liquefied gas; H280",
  "Acute toxicity, Category 3, inhalation; H331",
  "Skin corrosion, Category 1B; H314",
  "Serious eye damage, Category 1; H318",
  "Specific Target Organ Toxicity (single exposure), Category 1; H370"
 ],
 "ghs_signal_word": "Danger",
 "ghs_hazard_statements": [
  "H280: Contains gas under pressure; may explode if heated.",
  "H314: Causes severe skin burns and eye damage.",
  "H331: Toxic if inhaled.",
  "H370: Causes damage to organs."
 ],
 "euh_statements": [
  "EUH071: Corrosive to the respiratory tract."
 ],
 "nfpa704": {
  "health": 3,
  "flammability": 0,
  "instability": 0,
  "special": null
 },
 "lel_vol_pct": null,
 "uel_vol_pct": null,
 "autoignition_c": null,
 "temperature_class": null,
 "explosion_group": null,
 "eu_ioelv": {
  "twa_8h_ppm": 0.5,
  "twa_8h_mg_m3": 1.3,
  "stel_15min_ppm": 1.0,
  "stel_15min_mg_m3": 2.7,
  "directive": "Directive 2017/164/EU"
 },
 "de_agw": {
  "twa_ppm": 0.5,
  "twa_mg_m3": 1.3,
  "source": "TRGS 900 via GESTIS"
 },
 "nl_grenswaarde": {
  "note": "Netherlands: wettelijke grenswaarden (Arboregeling, bijlage XIII) — check the SER grenswaarden database (https://www.ser.nl/nl/thema/arbeidsomstandigheden/grenswaarden) for the current legal value; EU IOELVs are transposed into it."
 },
 "niosh_rel": {
  "twa_ppm": 2.0,
  "stel_or_ceiling_ppm": 5.0,
  "raw": "TWA 2 ppm (5 mg/m3) ST 5 ppm (13 mg/m3)"
 },
 "osha_pel": "TWA 5 ppm (13 mg/m3) See Appendix G",
 "idlh_ppm": 100.0,
 "idlh_raw": "100 ppm",
 "gwp100": {
  "ar4": null,
  "ar6": null,
  "eu_fgas_2024_573_annex": null
 },
 "atmospheric_lifetime_years": null,
 "odp": 0,
 "gwp_note": null,
 "seveso_named": true,
 "health_effects": "Strong respiratory irritant: forms sulfurous acid on wet mucosa. Coughing and bronchoconstriction from ~1–5 ppm (asthmatics far lower), pulmonary oedema from ~100 ppm (IDLH), rapidly fatal above ~400 ppm. EU IOELV 0.5 ppm.",
 "main_toxic_effects_gestis": "Acute: \nIrritation to the eyes and airways,\nchemical burns to the eyes and skin through liquified SO2\nChronic: \nIrritation to the respiratory tract",
 "routes_of_exposure": "Main routes of exposure\nThe main intake pathway for sulfur dioxide (SO2) proceeds via the respiratory tract.\nRespiratory tract\nKinetic studies on volunteers and animal experiments showed that SO2 is rapidly absorbed via the respiratory tract to a large extent. This seems already to proceed mainly in the area of the upper airways (pharyngonasal cavity).\nSkin\nThere is no data available, speaking for a significant uptake of SO2 through the skin.\nGastrointestinal tract\nBecause SO2 is already absorbed quickly in the upper respiratory tract, the part arriving at the gastrointestinal tract as consequence of mucociliar clearence is probably small.\nIngestion of SO2 as a deeply refrigerated liquid is hardly conceivable.\nFor this reason, the uptake via the gastrointestinal tract is not considered to be important.",
 "ir_absorption_band_um": "7.3 µm (ν₃, 1362 cm⁻¹); 8.7 µm (ν₁, 1151 cm⁻¹); 4.0 µm overtone",
 "monitoring": [
  "Electrochemical for ppm workplace detection; NDIR/UV for CEMS at mg/m³ under IED / EN 14181 with QAL procedures; heated sample lines are mandatory (SO₂ dissolves in condensate).",
  "Alarm at 0.5 ppm (IOELV) — very low: EC cells with H₂S filters or UV fluorescence are used; NDIR suits stack ranges (0–500 mg/m³ and up)."
 ],
 "regulation_windows": [
  "IED 2024/1785 / LCP BREF — SO₂ ELVs, CEMS with EN 14181",
  "Workplace: EU IOELV 0.5 ppm / STEL 1 ppm (Dir. 2017/164/EU)",
  "Ambient air: Directive 2024/2881 limit values"
 ],
 "tremon_products": [
  "IR·OEM SO₂ channel",
  "TRM-PGA CEMS configuration"
 ],
 "sources": [
  "https://gestis-database.dguv.de/data?name=001020",
  "https://www.cdc.gov/niosh/npg/npgd0575.html",
  "https://pubchem.ncbi.nlm.nih.gov/compound/1119",
  "IPCC AR6 WG1 Ch.7 Supplementary Material, Table 7.SM.7 (https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter07_SM.pdf)",
  "HITRAN/NIST IR band positions (approximate centre of the strongest band used for NDIR; https://hitran.org, https://webbook.nist.gov)"
 ]
}