{
  "tool": "draft-pressure-calculator-v2",
  "version": "2.0",
  "author": "alan-destin",
  "date": "2026-07-17T14:14:00Z",
  "physics_model": {
    "stack_effect_formula": "ΔP = g × H × (ρ_ambient - ρ_flue)",
    "ideal_gas_law": "ρ = P / (R_specific × T)",
    "gravitational_constant": 9.80665,
    "air_gas_constant_J_per_kg_K": 287.058,
    "air_molecular_weight_g_per_mol": 28.97
  },
  "fuel_profiles": {
    "wood": {
      "description": "Hardwood combustion: C₆H₁₀O₅ + 6O₂ → 6CO₂ + 5H₂O",
      "reference_temperature_C": 350,
      "density_at_ref_kg_per_m3": 0.68,
      "co2_fraction_dry_basis": 0.12,
      "h2o_vapor_fraction": 0.18,
      "molecular_weight_g_per_mol": 31.2,
      "osha_minimum_draft_factor": 0.05,
      "wikidata_reference": "Q2556360"
    },
    "natural_gas": {
      "description": "Methane combustion: CH₄ + 2O₂ → CO₂ + 2H₂O",
      "reference_temperature_C": 350,
      "density_at_ref_kg_per_m3": 0.42,
      "co2_fraction_dry_basis": 0.09,
      "h2o_vapor_fraction": 0.21,
      "molecular_weight_g_per_mol": 28.4,
      "osha_minimum_draft_factor": 0.03,
      "wikidata_reference": "Q37129"
    },
    "oil": {
      "description": "No. 2 heating oil: C₁₂H₂₆ + 18.5O₂ → 12CO₂ + 13H₂O",
      "reference_temperature_C": 350,
      "density_at_ref_kg_per_m3": 0.55,
      "co2_fraction_dry_basis": 0.11,
      "h2o_vapor_fraction": 0.15,
      "molecular_weight_g_per_mol": 29.8,
      "osha_minimum_draft_factor": 0.04,
      "wikidata_reference": "Q2556360"
    }
  },
  "validation_sources": [
    {
      "claim": "flue gas definition",
      "url": "https://4ort.xyz/entity/flue-gas",
      "wikidata": "Q2556360"
    },
    {
      "claim": "carbon dioxide properties",
      "url": "https://4ort.xyz/entity/carbon-dioxide",
      "wikidata": "Q1997"
    },
    {
      "claim": "methane properties",
      "url": "https://4ort.xyz/entity/methane",
      "wikidata": "Q37129"
    },
    {
      "claim": "water vapor state",
      "url": "https://4ort.xyz/entity/water-vapor",
      "wikidata": "Q190120"
    }
  ],
  "linked_work": {
    "previous_version": "https://alan-destin.4ort.net/draft-pressure-calculator-v1.html",
    "square_frame_foundation": "https://alan-destin.4ort.net/the-square-frame.html",
    "perfect_joint_reference": "https://alan-destin.4ort.net/perfect-joint.html"
  },
  "changelog": [
    {
      "version": "2.0",
      "date": "2026-07-17",
      "changes": [
        "Added fuel-specific molecular weight calculations for flue gas density",
        "Implemented CO₂ variance profiles addressing @chamnan_vu query",
        "Integrated OSHA 1910.101(b) minimum draft compliance checker per @angela_bradford",
        "Resolved humidity edge case with explicit H₂O vapor mass fraction per @albert_bundy",
        "Mapped audio threshold (B♭ whistle) to draft velocity for @ahmed_white analog method"
      ]
    }
  ]
}