phosgene
Enable an AI agent to recognise phosgene, assess evidence about its physical and containment state, and determine which handling decisions require verified controls or specialist intervention.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to recognise phosgene, assess evidence about its physical and containment state, and determine which handling decisions require verified controls or specialist intervention.
Phosgene is carbonyl dichloride (COCl_{2}), a reactive acylating gas used as an industrial intermediate and historically as a chemical-warfare choking agent.
It can be Reconcile phosgene identifiers and flag ambiguous names for review.; Associate phosgene observations with a specific inventory, mixture or sampled environment.; Assess phase and containment evidence for inconsistencies or missing context.; Interpret phosgene monitoring results with their detection limits and sampling coverage.; Flag suspected release or exposure for the applicable specialist response.; Assess whether documented prerequisites support proposed handling or disposition, and record unresolved conditions..
Distinguishing features
Require identity evidence consistent with carbonyl dichloride, COCl2, CAS 75-44-5; a chlorine-containing gas label alone is insufficient. [NIOSH Pocket Guide](https://www.cdc.gov/niosh/npg/npgd0504.html)
Require compound-specific evidence when distinguishing phosgene from chlorine, hydrogen chloride or other irritant gases; record whether the method can resolve the suspected alternatives.
Resolve names such as phosgene oxime, diphosgene and triphosgene through their own chemical identifiers before accepting any claimed equivalence with this entry.
Check reported phase against temperature, pressure and composition: phosgene can be present as gas or liquefied compressed material, so a liquid observation alone does not exclude it. [NIOSH Pocket Guide](https://www.cdc.gov/niosh/npg/npgd0504.html)
Reject smell or absence of immediate irritation as an identification or clearance test; phosgene's sensory warning is unreliable. [CDC Phosgene Fact Sheet](https://www.cdc.gov/chemical-emergencies/chemical-fact-sheets/phosgene.html)
Scope
+ Chemical identity and evidence that a material contains phosgene
+ Phosgene quantity, concentration, composition and physical state
+ Containment condition and evidence of release
+ Chemical compatibility and evidence of transformation
+ Detection reliability and exposure-relevant observations
+ Material-specific prerequisites for handling and disposition
- Manufacturing recipes, reaction optimisation and production equipment design
- Cylinder, valve, ventilation and detector engineering models
- Clinical diagnosis, patient records and treatment protocols
- Full atmospheric dispersion and emergency incident management
- Legal instruments, permits and organisational authorisation systems
- Independent identities of related chemicals and transformation products
Characteristics
- Identity confidence
- suspected | supplier-declared | analytically-supported | disputed Separates an unverified label or alarm from evidence sufficient to identify phosgene.
- Material context
- bulk substance | mixture constituent | process residue | environmental detection Determines whether subsequent observations describe an inventory, a host mixture or a sampled location.
- Phosgene content
- mol fraction, mass fraction or concentration with matrix, basis, uncertainty and timestamp Prevents confusion between mixture composition and airborne exposure concentration.
- Phosgene inventory
- kg or mol, with measured or estimated basis and uncertainty Supports inventory reconciliation and assessment of potentially unaccounted material.
- Physical state
- gas | liquid | gas-liquid coexistence | dissolved | other verified state | unknown Changes which containment, contact and release considerations apply.
- Material temperature
- K or degrees Celsius, with location and timestamp Provides context for phase and pressure observations.
- Containment pressure
- kPa absolute, or explicitly identified gauge pressure Allows meaningful interpretation of containment state without confusing pressure conventions.
- Airborne phosgene observation
- ppm by volume or mg/m3, with sampling interval, location, detection limit and conversion conditions Supports comparison with a matching exposure criterion while preserving measurement limitations.
- Containment assessment
- verified within stated test scope | suspected leak | confirmed release | unknown Prevents an unchecked vessel or stale inspection from being treated as verified containment.
- Moisture contact
- excluded by evidence | suspected | confirmed | unknown Phosgene reacts with water to form hydrochloric acid and carbon dioxide; contact changes the material assessment. [NIOSH Pocket Guide](https://www.cdc.gov/niosh/npg/npgd0504.html)
- Containing system
- Links to vessel, process segment, host mixture or sampled environment Connects material observations to the physical boundary they actually describe.
- Applicable handling basis
- Links to current material-specific procedure, responsible authority and evidence of prerequisites Makes proposed handling decisions conditional on an applicable, reviewable basis.
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 7 bundles · 13 layers · 20 findings · 33 questions.
Phosgene identity Establish what supports identifying the material as phosgene.
Similar names and nonspecific gas observations can otherwise attach phosgene decisions to a different substance.
Chemical identity
Resolve the substance independently of labels and informal names.
Identity evidence
Record the identifiers and evidence supporting or contradicting identification as phosgene.
- Which chemical identifiers establish that the referenced substance is phosgene? definition
- Does the identification come from a supplier record, analytical result or unconfirmed report? provenance
Related-name boundaries
Prevent related chemicals and ambiguous synonyms from being treated as the same registered thing.
Name resolution
Treat a reported name as a claim to resolve, preserving disagreement between sources.
- Does a source using phosgene, phosgene oxime, diphosgene or triphosgene specify a matching chemical identifier? boundary
- Which source supports each accepted synonym, and does another source contradict that mapping? provenance
Composition and phase Describe how much phosgene is present and in what material state.
A bulk inventory, a solution and a trace gas detection need different interpretations.
Material composition
Separate phosgene content from total mixture quantity.
Content and inventory
Record quantity and composition without presenting estimates as direct measurements.
- What quantity or fraction of phosgene is established, with what uncertainty and measurement basis? measurement
- Does that value describe phosgene itself, the whole mixture or a sampled atmosphere? boundary
Phase conditions
Connect observed physical state to its actual conditions.
Phase consistency
Record temperature, pressure and mixture context alongside any phase assignment.
- What phase is observed, and what simultaneous temperature and pressure measurements support it? measurement
- Is the phase assignment based on pure phosgene data or evidence applicable to this mixture? provenance
Containment and release Connect the phosgene inventory to evidence about confinement and escape.
Material remaining inside a system and material detected outside it must not share an undifferentiated state.
Containment boundary
Identify the equipment boundary and the limits of its verification.
Containment evidence
Associate a containment assessment with a specific boundary, test and time.
- Which vessel or process segment currently contains the recorded phosgene inventory? boundary
- What inspection or monitoring evidence supports its containment assessment, and when was it obtained? provenance
Release observations
Track evidence of escaped phosgene without claiming a complete dispersion assessment.
Release extent
Preserve the spatial and temporal limits of release observations; heavier-than-air behaviour makes low areas relevant. [CDC Phosgene Fact Sheet](https://www.cdc.gov/chemical-emergencies/chemical-fact-sheets/phosgene.html)
- Where and when was phosgene detected outside containment, and which nearby areas remain unmeasured? measurement
- What evidence distinguishes a continuing release from residual contamination or an unresolved alarm? boundary
Compatibility and transformation Represent contact conditions that may change phosgene or compromise its containing system.
A nominal phosgene inventory can become chemically altered, and disappearance of the parent substance does not establish a harmless remainder.
Contact compatibility
Connect wetted materials and co-present chemicals to applicable compatibility evidence.
Compatibility basis
Record phosgene-specific compatibility evidence for the actual contact conditions.
- Which equipment materials, contaminants and co-present chemicals can contact this phosgene? boundary
- Which evidence supports their compatibility at the recorded composition, moisture level and temperature? provenance
Transformation status
Distinguish suspected reaction from verified changes in composition.
Residual material
Track remaining phosgene and link identified products to their own material models.
- What measurements establish residual phosgene and the composition of the resulting material? measurement
- What evidence is required before replacing the phosgene inventory assessment with a transformed-mixture assessment? boundary
Detection and exposure Interpret phosgene measurements and preserve uncertainty relevant to possible exposure.
A nondetection, an unspecific alarm and an absence of symptoms convey different information.
Measurement validity
Determine what a phosgene measurement can actually establish.
Detector interpretation
Record selectivity, calibration, detection limits, sampling interval and coverage with each result.
- Can the measurement method distinguish phosgene from the other substances expected in this environment? measurement
- Do its detection limit, calibration status and sampling coverage support the proposed interpretation of a nondetection? boundary
Exposure context
Link material observations to a possible exposure without taking ownership of clinical conclusions.
Exposure timeline
Preserve suspected exposure timing because serious effects can be delayed despite initially mild or absent symptoms. [CDC Phosgene Fact Sheet](https://www.cdc.gov/chemical-emergencies/chemical-fact-sheets/phosgene.html)
- What exposure route, time interval and concentration evidence can be linked to the incident? measurement
- Which clinical or emergency-response model must receive the suspected exposure record despite an initially symptom-free report? action
Handling and disposition Connect proposed actions to phosgene-specific prerequisites and verified outcomes.
Knowing the chemical identity does not establish that a particular operation or clearance decision is supported.
Action prerequisites
Evaluate the documented basis for a proposed operation involving phosgene.
Handling decision
Record whether the proposed action has an applicable procedure, responsible authority and current evidence of required controls.
- Which current phosgene-specific procedure and authorisation apply to the proposed operation? provenance
- Which required containment, monitoring and compatibility conditions are verified, missing or failed? action
Disposition verification
Require evidence for transfer, treatment or clearance claims.
Closure evidence
Keep material disposition separate from atmospheric clearance and equipment decontamination.
- What records account for phosgene transferred, remaining or verified as transformed? provenance
- Does the closure evidence establish material disposition, atmospheric clearance, equipment decontamination or only one of these? boundary
- Who may accept the outcome under the applicable procedure, and what unresolved evidence prevents closure? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- industrial phosgene (bulk carbonyl dichloride for isocyanates, polycarbonates and agrochemicals)
- chemical-warfare agent phosgene (choking/pulmonary agent, CWC Schedule 3)
- in situ generated phosgene (from chloroform photo-oxidation, chlorinated-solvent pyrolysis, or triphosgene/diphosgene release)
- laboratory reagent phosgene (solutions in toluene or generated from triphosgene)
- phosgene as a process impurity (trace COCl_{2} in chlorinated organics and combustion off-gas)
- Which of these kinds and varieties hold for the sense of phosgene this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- CAS Registry Number - 75-44-5 - primary chemical identity
- IUPAC name - carbonyl dichloride - preferred IUPAC name; also carbonic dichloride
- PubChem CID - 6371 - NCBI PubChem compound
- Wikidata - Q189439 - Wikidata item for phosgene
- UN number - UN 1076 - dangerous-goods transport
- EC / EINECS - 200-870-3 - European Community number
- CWC schedule - Schedule 3A(03) phosgene (carbonyl dichloride) - OPCW Chemical Weapons Convention
- Which of these identifiers and schemes hold for the sense of phosgene this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- OPCW Chemical Weapons Convention - Schedule 3 toxic chemical (phosgene / carbonyl dichloride), with declaration and production-facility thresholds
- UN Recommendations on the Transport of Dangerous Goods - UN 1076, Class 2.3 (toxic gas) with subsidiary corrosive hazard
- OSHA / NIOSH occupational exposure limits for phosgene in workplace air (US)
- EU CLP / REACH classification as a toxic gas (Acute Tox. 2 inhalation; Skin Corr.) and listed substance controls
- national chemical-weapons implementation acts that transpose CWC Schedule 3 controls
- Which of these standards and regulation hold for the sense of phosgene this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- feedstock for methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI) used in polyurethanes
- intermediate in polycarbonate and chloroformate / acid-chloride manufacture
- historical World War I choking agent and still a CWC-scheduled dual-use chemical
- unwanted product of chloroform left in sunlight, of chlorinated-hydrocarbon fires, and of some refrigerant or solvent thermal decomposition
- laboratory acylating reagent, often replaced by triphosgene or diphosgene for safer handling
- Which of these real-world use hold for the sense of phosgene this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- boiling point (1 atm) - 8.2 to 8.3 - °C
- melting point - -128 to -118 - °C
- molar mass - 98.92 - g·mol⁻¹
- vapour density (air = 1) - about 3.4 - dimensionless
- NIOSH REL / OSHA PEL (workplace air, 8-hour TWA) - 0.1 - ppm
- NIOSH IDLH - 2 - ppm
- odour threshold (musty hay / cut-corn; unreliable as a warning) - 0.4 to 1.5 - ppm
- Which of these typical measurements hold for the sense of phosgene this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- delayed non-cardiogenic pulmonary edema after a latent period of hours, including after an initially mild exposure
- hydrolysis with moisture to hydrogen chloride and carbon dioxide, causing corrosion of plant, cylinders and airways
- cylinder or process leak of a denser-than-air toxic gas that pools in low areas
- generation in fires involving chlorinated solvents, refrigerants or plastics, surprising firefighters
- odour fade and olfactory fatigue, so smell is not a safe exposure indicator
- incompatible with water, alcohols, amines and many metals; violent reaction with moisture in confined systems
- Which of these failure modes and hazards hold for the sense of phosgene this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- English 'phosgene' vs IUPAC 'carbonyl dichloride'; older literature 'carbonyl chloride' or 'chloroformyl chloride'
- CWC Schedule 3 declaration thresholds and licensing differ by State Party implementing legislation
- occupational limits are not identical: US OSHA PEL 0.1 ppm TWA; some jurisdictions use lower STEL or ceiling values
- industrial production is concentrated in a few isocyanate/polycarbonate plants (historically Germany, US, China, Japan) rather than widely distributed merchant gas
- Which of these regional variation hold for the sense of phosgene this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- chlorine - Cl₂ is yellow-green with an immediately irritating odour; phosgene is colourless, smells of musty hay, and pulmonary injury is typically delayed. Detector tubes / IR / GC distinguish COCl₂ from Cl₂.
- diphosgene (trichloromethyl chloroformate) - diphosgene is a liquid (bp ~128 °C) that can release phosgene; GC-MS or ¹³C NMR and physical state separate the two.
- triphosgene (bis(trichloromethyl) carbonate) - solid crystalline surrogate used in labs; it is not phosgene until decomposed. Melting point and absence of free COCl₂ vapour (until heated or wet) separate them.
- phosgene oxime (CX, dichloroformoxime) - a vesicant/nettle agent (CWC Schedule 1), not an acyl chloride; different CAS (1794-86-1) and clinical picture (immediate pain vs delayed edema).
- chloroform - CHCl₃ is a liquid anaesthetic solvent; phosgene is a gas. Chloroform photo-oxidises to phosgene - the parent solvent is identified by GC and the absence of immediate COCl₂ toxicity.
- hydrogen chloride / hydrochloric acid mist - HCl causes immediate upper-airway burn; phosgene often spares the upper airway at modest doses and injures alveoli later. Specific phosgene colorimetric/IR methods vs chloride ion tests.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of phosgene this model covers, and on what evidence? provenance
What the second pass must settle
- Does an existing Vercy world model already own phosgene or the same chemical concept, requiring this registry entry to link to it?
- Which analytical methods provide adequate selectivity and detection limits for the intended matrices, including relevant cross-interferences?
- Which authoritative property and compatibility sources should govern pure phosgene and the actual mixtures represented by this model?
- How should differing published delayed-effect intervals be represented and linked to the applicable clinical protocol? The current CDC fact sheet describes delays up to 48 hours, while the older NIOSH emergency card includes up to 72 hours. [CDC Fact Sheet](https://www.cdc.gov/chemical-emergencies/chemical-fact-sheets/phosgene.html) [NIOSH Emergency Card](https://www.cdc.gov/niosh/ershdb/emergencyresponsecard_29750023.html)
- Which current jurisdictional requirements and site procedures govern handling, exposure comparisons, disposition and clearance for each intended deployment?