{"query":{"parameter":"sulfur dioxide","place":"US-SD","medium":null,"statistic":null,"kind":null},"searched":{"places":["US-SD","US"],"parameter_keys":["cas:7446-09-5","cas:33990-98-6","cas:102424-23-7","cas:65345-27-9"],"names_matched":[["sulfur dioxide","cas:7446-09-5"],["1 decene polymer with sulfur dioxide","cas:33990-98-6"],["2 2 oxybisethanol reaction products with ammonia morpholine derivs residues reaction products with sulfur dioxide","cas:102424-23-7"],["ethanol 2 2 oxybis reaction products with ammonia morpholine derivs residues reaction products with sulfur dioxide","cas:102424-23-7"],["2 aminoethanol compound with sulphur dioxide 1 1","cas:65345-27-9","sulphur dioxide"]],"match":"exact+contains","order":"The place's own instruments first, then each place above it, each in its register's order"},"total":3,"offset":0,"returned":3,"next_offset":null,"rows":[{"id":"9d137cfa33e35cce","parameter":"sulfur dioxide","value":"0.5","value_num":0.5,"unit":"ppm","direction":"max","kind":"limit","medium":"ambient_air","level":"national","parameter_key":"cas:7446-09-5","place":["US"],"conditions":["not to be exceeded more than once per calendar year"],"cite":{"instrument":"us_naaqs","title":"40 CFR Part 50, National Primary and Secondary Ambient Air Quality Standards, §§ 50.4–50.21 (eCFR as of 2026-08-01)","issuer":null,"edition":"90 FR 4651, Jan. 16, 2025","source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-40.xml?part=50","source_sha256":null,"fetched_at":null,"source_status":{"checked":"2026-10-15","status":"unchanged"},"section":"§ 50.5 National secondary ambient air quality standard for sulfur oxides (sulfur dioxide).","page":null,"quote":"(a) The level of the 3-hour standard is 0.5 parts per million (ppm), not to be exceeded more than once per calendar year.","column":"valeur"}},{"id":"08c21282ea9a38f6","parameter":"sulfur dioxide","value":"75","value_num":75,"unit":"ppb","direction":"max","kind":"limit","medium":"ambient_air","level":"national","parameter_key":"cas:7446-09-5","place":["US"],"conditions":["three-year average of the annual (99th percentile) of the daily maximum 1-hour average concentrations"],"cite":{"instrument":"us_naaqs","title":"40 CFR Part 50, National Primary and Secondary Ambient Air Quality Standards, §§ 50.4–50.21 (eCFR as of 2026-08-01)","issuer":null,"edition":"90 FR 4651, Jan. 16, 2025","source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-40.xml?part=50","source_sha256":null,"fetched_at":null,"source_status":{"checked":"2026-10-15","status":"unchanged"},"section":"§ 50.17 National primary ambient air quality standards for sulfur oxides (sulfur dioxide).","page":null,"quote":"(a) The level of the national primary 1-hour annual ambient air quality standard for oxides of sulfur is 75 parts per billion (ppb, which is 1 part in 1,000,000,000), measured in the ambient air as sulfur dioxide (SO 2 ).","column":"valeur"}},{"id":"0049bd8fe957ede0","parameter":"sulfur dioxide","value":"10","value_num":10,"unit":"ppb","direction":"max","kind":"limit","medium":"ambient_air","level":"national","parameter_key":"cas:7446-09-5","place":["US"],"conditions":["3-year average of the annual SO 2 concentration"],"cite":{"instrument":"us_naaqs","title":"40 CFR Part 50, National Primary and Secondary Ambient Air Quality Standards, §§ 50.4–50.21 (eCFR as of 2026-08-01)","issuer":null,"edition":"90 FR 4651, Jan. 16, 2025","source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-40.xml?part=50","source_sha256":null,"fetched_at":null,"source_status":{"checked":"2026-10-15","status":"unchanged"},"section":"§ 50.21 National secondary ambient air quality standards for sulfur oxides (sulfur dioxide).","page":null,"quote":"(a) The level of the annual secondary national ambient air quality standard for oxides of sulfur is 10 parts per billion (ppb), measured in the ambient air as sulfur dioxide (SO 2 )","column":"valeur"}}],"next":[{"tool":"check_values","says":"Has your user measured this? check_values sets each of their results beside every row held here, with a verdict and the row's cite.","arguments":{"place":"US-SD"},"needs":{"rows":"Your user's measured results, as their table prints them: [{parameter: \"sulfur dioxide\", value, unit}, ...], any other parameters too."},"post":"/api/v1/check"},{"tool":"read_certificate","says":"Has your user a laboratory certificate? read_certificate reads every row it prints, each with its page, and checks them against these limits.","arguments":{"place":"US-SD"},"needs":{"content_base64":"The laboratory's certificate (PDF) or its XLSX, XLS or CSV export, as base64; or file_url, a public https address of it."},"post":"/api/v1/certificate"}]}