Adds equations 50-18, 50-19 and 50-20 of the SFPE handbook.

crates/python_api/docs/api/sfpe-handbook.rst

@@ -104,6 +104,29 @@ Equation 50.16 - Flow Area Factor for Pressurization Systems
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 .. automodule:: ofire.sfpe_handbook.chapter_50.equation_50_16
+   :members:
+   :undoc-members:
+   :show-inheritance:
+
+Equation 50.18 - Fractional Effective Dose
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. automodule:: ofire.sfpe_handbook.chapter_50.equation_50_18
+   :members:
+   :undoc-members:
+   :show-inheritance:
+
+Equation 50.19 - Visibility Through Uniform Smoke
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. automodule:: ofire.sfpe_handbook.chapter_50.equation_50_19
+   :members:
+   :undoc-members:
+   :show-inheritance:
+Equation 50.20 - Visibility Through Smoke (Percent Obscuration)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. automodule:: ofire.sfpe_handbook.chapter_50.equation_50_20
    :members:
    :undoc-members:
    :show-inheritance:

crates/python_api/docs/guide/equation-relationships.rst

@@ -61,8 +61,18 @@ Visibility
 
 These equations calculate visibility distance through smoke but use different formulations:
 
-- :func:`ofire.cibse_guide_e.chapter_10.equation_10_7.visibility` - CIBSE Guide E, Chapter 10, Equation 10.7 (uses extinction coefficient and optical density: k/(2.303×d))
-- :func:`ofire.fire_dynamics_tools.chapter_18.equation_18_1.visibility` - Fire Dynamics Tools, Chapter 18, Equation 18.1 (uses extinction coefficient, mass extinction coefficient, and particulate concentration: k/(αₘ×mₚ))
+- :func:`ofire.cibse_guide_e.chapter_10.equation_10_7.visibility` - CIBSE Guide E, Chapter 10, Equation 10.7
+- :func:`ofire.fire_dynamics_tools.chapter_18.equation_18_1.visibility` - Fire Dynamics Tools, Chapter 18, Equation 18.1
+
+Fractional Effective Dose
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+*Group 3: Fractional Effective Dose Calculations*
+
+These equations calculate the fractional effective dose (FED), representing accumulated toxic exposure over time as a fraction of the lethal dose, but use different formulations:
+
+- :func:`ofire.sfpe_handbook.chapter_50.equation_50_18.fed` - SFPE Handbook, Chapter 50, Equation 50-18
+- :func:`ofire.cibse_guide_e.chapter_10.equation_10_8.fractional_effective_dose` - CIBSE Guide E, Chapter 10, Equation 10-8
 
 Contributing to Equation Relationships
 ---------------------------------------

crates/python_api/src/sfpe_handbook/chapter_50.rs

@@ -2,7 +2,10 @@ pub mod equation_50_1;
 pub mod equation_50_14;
 pub mod equation_50_15;
 pub mod equation_50_16;
+pub mod equation_50_18;
+pub mod equation_50_19;
 pub mod equation_50_2;
+pub mod equation_50_20;
 pub mod equation_50_4;
 pub mod equation_50_6;
 pub mod equation_50_7;
@@ -21,5 +24,8 @@ pub fn chapter_50(m: &Bound<'_, PyModule>) -> PyResult<()> {
     m.add_wrapped(wrap_pymodule!(equation_50_14::equation_50_14))?;
     m.add_wrapped(wrap_pymodule!(equation_50_15::equation_50_15))?;
     m.add_wrapped(wrap_pymodule!(equation_50_16::equation_50_16))?;
+    m.add_wrapped(wrap_pymodule!(equation_50_18::equation_50_18))?;
+    m.add_wrapped(wrap_pymodule!(equation_50_19::equation_50_19))?;
+    m.add_wrapped(wrap_pymodule!(equation_50_20::equation_50_20))?;
     Ok(())
 }

crates/python_api/src/sfpe_handbook/chapter_50/equation_50_18.rs

@@ -0,0 +1,49 @@
+use pyo3::prelude::*;
+use pyo3::wrap_pyfunction;
+
+use openfire::sfpe_handbook::chapter_50::equation_50_18 as rust_equation_50_18;
+
+#[pyfunction]
+/// Fractional Effective Dose (FED) calculation for evaluation of exposure to smoke.
+///
+/// .. math::
+///
+///    FED = \frac{\sum (C_i \Delta t_i)}{LCt_{50}}
+///
+/// where:
+///
+/// - :math:`FED` is the fractional effective dose (dimensionless)
+/// - :math:`C_i` is the mass concentration of material burned at the end of time interval i (g/m³)
+/// - :math:`\Delta t_i` is the time interval i (s)
+/// - :math:`LC_{t50}` is the lethal exposure dose from test data (g/m³)
+///
+/// Args:
+///     c_i (list[float]): Concentration values at each time interval (g/m³)
+///     delta_t_i (float): Time intervals (s)
+///     lc_t50 (float): Lethal exposure dose from test data (g/m³)
+///
+/// Returns:
+///     float: Fractional effective dose (dimensionless)
+///
+/// Assumptions:
+///     Uniform time intervals.
+///
+/// Limitations:
+///     Simplest model for evaluating exposure to smoke.
+///
+/// Example:
+///     >>> import ofire
+///     >>> c_i = [0.001, 0.002, 0.003]
+///     >>> delta_t_i = 1.0
+///     >>> lc_t50 = 10.0
+///     >>> result = ofire.sfpe_handbook.chapter_50.equation_50_18.fed(c_i, delta_t_i, lc_t50)
+///     >>> print(f"{result:.2f}")
+fn fed(c_i: Vec<f64>, delta_t_i: f64, lc_t50: f64) -> PyResult<f64> {
+    Ok(rust_equation_50_18::fed(c_i, delta_t_i, lc_t50))
+}
+
+#[pymodule]
+pub fn equation_50_18(m: &Bound<'_, PyModule>) -> PyResult<()> {
+    m.add_function(wrap_pyfunction!(fed, m)?)?;
+    Ok(())
+}

crates/python_api/src/sfpe_handbook/chapter_50/equation_50_19.rs

@@ -0,0 +1,46 @@
+use pyo3::prelude::*;
+use pyo3::wrap_pyfunction;
+
+use openfire::sfpe_handbook::chapter_50::equation_50_19 as rust_equation_50_19;
+
+#[pyfunction]
+/// Visibility in smoke at a point where mass concentration of fuel burned is known.
+///
+/// .. math::
+///
+///    S_i = \frac{K}{2.303 {\delta}_m C_i}
+///
+/// where:
+///
+/// - :math:`S_i` is the visibility through smoke (m)
+/// - :math:`K` is the proportionality constant (dimensionless)
+/// - :math:`{\delta}_m` is the mass optical density (m²/g)
+/// - :math:`C_i` is the mass concentration of fuel burned (g/m³)
+///
+/// Args:
+///     k (float): Proportionality constant (dimensionless)
+///     delta_m (float): Mass optical density (m²/g)
+///     c_i (float): Mass concentration of fuel burned (g/m³)
+///
+/// Returns:
+///     float: Visibility through smoke (m)
+///
+/// Assumptions:
+///     The calculated visibility can be thought of as visibility if smoke is uniform.
+///
+/// Limitations:
+///     See assumptions above. Assumes uniform smoke and, utilises the proportionality constant K, commonly taken as 8 for illuminated signs and 3 for non-illuminated.
+///
+/// Example:
+///     >>> import ofire
+///     >>> result = ofire.sfpe_handbook.chapter_50.equation_50_19.visibility(8.0, 0.22, 1.0)
+///     >>> print(f"{result:.2f}")
+fn visibility(k: f64, delta_m: f64, c_i: f64) -> PyResult<f64> {
+    Ok(rust_equation_50_19::visibility(k, delta_m, c_i))
+}
+
+#[pymodule]
+pub fn equation_50_19(m: &Bound<'_, PyModule>) -> PyResult<()> {
+    m.add_function(wrap_pyfunction!(visibility, m)?)?;
+    Ok(())
+}

crates/python_api/src/sfpe_handbook/chapter_50/equation_50_20.rs

@@ -0,0 +1,46 @@
+use pyo3::prelude::*;
+use pyo3::wrap_pyfunction;
+
+use openfire::sfpe_handbook::chapter_50::equation_50_20 as rust_equation_50_20;
+
+#[pyfunction]
+/// Visibility calculation through smoke from percent obscuration.
+///
+/// .. math::
+///
+///    S_i = -\frac{K L}{\ln(1 - \frac{\lambda}{100})}
+///
+/// where:
+///
+/// - :math:`S_i` is the visibility through smoke (m)
+/// - :math:`K` is proportionality constant (dimensionless)
+/// - :math:`L` is the path length (m)
+/// - :math:`\lambda` is the percent obscuration (dimensionless)
+///
+/// Args:
+///     k (float): Proportionality constant (dimensionless)
+///     l (float): Path length (m)
+///     lambda (float): Percent obscuration (dimensionless)
+///
+/// Returns:
+///     float: Visibility through smoke (m)
+///
+/// Assumptions:
+///     An object can be seen for S > L.
+///
+/// Limitations:
+///     None stated.
+///
+/// Example:
+///     >>> import ofire
+///     >>> result = ofire.sfpe_handbook.chapter_50.equation_50_20.visibility(8.0, 10.0, 95.0)
+///     >>> print(f"{result:.2f}")
+fn visibility(k: f64, l: f64, lambda: f64) -> PyResult<f64> {
+    Ok(rust_equation_50_20::visibility(k, l, lambda))
+}
+
+#[pymodule]
+pub fn equation_50_20(m: &Bound<'_, PyModule>) -> PyResult<()> {
+    m.add_function(wrap_pyfunction!(visibility, m)?)?;
+    Ok(())
+}

crates/sfpe_handbook/src/chapter_50.rs

@@ -2,7 +2,10 @@ pub mod equation_50_1;
 pub mod equation_50_14;
 pub mod equation_50_15;
 pub mod equation_50_16;
+pub mod equation_50_18;
+pub mod equation_50_19;
 pub mod equation_50_2;
+pub mod equation_50_20;
 pub mod equation_50_4;
 pub mod equation_50_6;
 pub mod equation_50_7;

crates/sfpe_handbook/src/chapter_50/equation_50_18.rs

@@ -0,0 +1,27 @@
+pub fn fed(c_i: Vec<f64>, delta_t: f64, lc_t50: f64) -> f64 {
+    let numerator: f64 = c_i.iter().map(|c| c * delta_t).sum();
+    numerator / lc_t50
+}
+
+#[cfg(not(coverage))]
+pub fn fed_equation(fed: String, c_i: String, delta_t: String, lc_t50: String) -> String {
+    format!(
+        "{} = \\frac{{ \\sum {} \\times {} }}{{ {} }}",
+        fed, c_i, delta_t, lc_t50
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_fed() {
+        let c_i = vec![0.001, 0.003];
+        let delta_t = 1.0;
+        let lc_t50 = 0.015;
+        let result = fed(c_i, delta_t, lc_t50);
+        let expected = 0.266666667;
+        assert!((result - expected).abs() < 1e-6);
+    }
+}

crates/sfpe_handbook/src/chapter_50/equation_50_19.rs

@@ -0,0 +1,23 @@
+pub fn visibility(k: f64, delta_m: f64, c_i: f64) -> f64 {
+    k / (2.303 * delta_m * c_i)
+}
+
+#[cfg(not(coverage))]
+pub fn visibility_equation(s_i: String, k: String, delta_m: String, c_i: String) -> String {
+    format!(
+        "{} = \\frac{{{}}}{{2.303 \\times {} \\times {}}}",
+        s_i, k, delta_m, c_i,
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_visibility() {
+        let result = visibility(8.0, 0.22, 1.0);
+        let expected = 15.78968144;
+        assert!((result - expected).abs() < 1e-6);
+    }
+}

crates/sfpe_handbook/src/chapter_50/equation_50_20.rs

@@ -0,0 +1,23 @@
+pub fn visibility(k: f64, l: f64, lambda: f64) -> f64 {
+    -k * l / ((1.0 - lambda / 100.0).ln())
+}
+
+#[cfg(not(coverage))]
+pub fn visibility_equation(s_i: String, k: String, l: String, lambda: String) -> String {
+    format!(
+        "{} = \\frac{{{} \\times {}}}{{\\ln(1 - \\frac{{{}}}{{100}})}}",
+        s_i, k, l, lambda,
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_visibility() {
+        let result = visibility(8.0, 10.0, 95.0);
+        let expected = 26.70465606;
+        assert!((result - expected).abs() < 1e-6);
+    }
+}