P
PathoSim
High-Risk Facility Surface Contamination Modeling • Full 3D Floor/Walls/Ceiling + Airflow
CBI INTELLIGENCE
v3.6 • Professional Edition • Simultaneous 3D Multi-Surface Simulation + Directional Region Indicators • Enhanced HVAC + ASHRAE 170 Compliance • Emergency & Waiting Room Algorithms • ASHRAE 170 / CDC / WHO / EPA Compliant
SIMULATION PARAMETERS
ROOM GEOMETRY + 3D SPACE DEFINITION
50
3.0
DEFINE 3D SPACE (Floor / Walls / Ceiling)
7.07
7.07
Floor: 50.0 m²
Walls: 84.8 m²
Ceiling: 50.0 m²
Total 3D Surfaces: 184.8 m²
Standard
ENVIRONMENTAL CONDITIONS
22.0
25.0
50
CONTAMINATION SOURCES
25
5
20
15
MITIGATION & VENTILATION
2.0
0
0
0
0
100
40
12
24
Speed
Surface View:
Time:
0
h
LOW RISK
CEILING STARTS HERE ↑
FLOOR STARTS HERE ↓
WALLS (NORTH/WEST)
WALLS (SOUTH/EAST)
Full 3D Multi-Surface Heatmap (Floor + Walls + Ceiling simulated simultaneously)
0
100+
12.4
AVG
units/m²
units/m²
Biofilm Maturity:
0%
TOTAL EST. LOAD
620
units in room
Average surface concentration × total cleanable area (3D weighted burden)
DOUBLING TIME
—
hours
Time required for microbial load to double at current net growth rate
AIRBORNE INDEX
4.2
units/m³
Airborne microbial concentration (surfaces + water + traffic, decayed by controls)
PATHOGEN GROWTH CURVES (multi-species + quorum + biofilm + 3D airflow adjusted)
Cumulative load over simulation period
🧪 SAMPLING, ANALYSIS, ACTION & 3D SURFACE-SPECIFIC DISINFECTION PROTOCOL
📋 HIGH RISK FACILITIES REPORT DETAILS SUMMARY
Deterministic multi-pathogen model with simultaneous Floor/Walls/Ceiling growth + 3D airflow modeling + hospital layouts • HEPA + UV-C + Ozone + Chlorine • Quorum Sensing + HVAC Airflow • Biofilm Visualization • Results for training & planning only
PathoSim Science Guide & Derivations – 3D Edition (v3.6)
Complete mathematical models • Simultaneous Floor/Walls/Ceiling + Enhanced HVAC Airflow + ASHRAE 170 Compliance • All Parameters & Room Types Fully Explained with Biofilm Mechanisms
1. All Parameters – Detailed Descriptions, Mathematical Derivations, ASHRAE 170 Compliance & References
Surface Area (m²)
Total cleanable surface area (floors + benches + equipment). Directly scales TOTAL EST. LOAD = average concentration × area. ASHRAE 170-2021 §6.2 requires minimum cleanable area calculations for infection control. Formula: TotalBurden = avgLoad × area.
Ref: CDC 2023 Surface Sampling Guidelines; ASHRAE 170-2021 §6.2
Total cleanable surface area (floors + benches + equipment). Directly scales TOTAL EST. LOAD = average concentration × area. ASHRAE 170-2021 §6.2 requires minimum cleanable area calculations for infection control. Formula: TotalBurden = avgLoad × area.
Ref: CDC 2023 Surface Sampling Guidelines; ASHRAE 170-2021 §6.2
Room Height (m)
Air volume = length × width × height. Used for settling velocity calculation (Stokes law 0.3 m/s) and ceiling deposition time. Higher ceilings increase ceiling deposition time. ASHRAE 170 mandates ceiling height for airflow patterns.
Ref: ASHRAE 170-2021 §5.1
Air volume = length × width × height. Used for settling velocity calculation (Stokes law 0.3 m/s) and ceiling deposition time. Higher ceilings increase ceiling deposition time. ASHRAE 170 mandates ceiling height for airflow patterns.
Ref: ASHRAE 170-2021 §5.1
Room Length / Width (m)
Precise 3D geometry for directional deposition modeling. Floor settling highest on north/south walls in standard HVAC flow. ASHRAE Handbook HVAC Applications Ch. 7 uses these for CFD-validated airflow modeling.
Ref: ASHRAE Handbook—HVAC Applications 2023 Ch. 7
Precise 3D geometry for directional deposition modeling. Floor settling highest on north/south walls in standard HVAC flow. ASHRAE Handbook HVAC Applications Ch. 7 uses these for CFD-validated airflow modeling.
Ref: ASHRAE Handbook—HVAC Applications 2023 Ch. 7
Hospital Room Layout
Revised algorithms: ER (1.35 – high floor deposition), Waiting Room (1.15 – uniform airborne), ICU (1.3 – negative pressure), OR (0.85 – positive pressure ceiling). All per ASHRAE 170 Table 7-1. Compliance enforced in simulation code.
Ref: ASHRAE 170-2021 Table 7-1; CDC Environmental Infection Control 2023
Revised algorithms: ER (1.35 – high floor deposition), Waiting Room (1.15 – uniform airborne), ICU (1.3 – negative pressure), OR (0.85 – positive pressure ceiling). All per ASHRAE 170 Table 7-1. Compliance enforced in simulation code.
Ref: ASHRAE 170-2021 Table 7-1; CDC Environmental Infection Control 2023
Air Temperature (°C)
Gaussian growth curve: g = base × exp(−((T−Topt)/σ)²). ASHRAE 170 requires 20–24°C patient rooms for comfort and microbial control.
Ref: WHO Microbial Kinetics 2022; ASHRAE 170-2021 §6.4
Gaussian growth curve: g = base × exp(−((T−Topt)/σ)²). ASHRAE 170 requires 20–24°C patient rooms for comfort and microbial control.
Ref: WHO Microbial Kinetics 2022; ASHRAE 170-2021 §6.4
Water System Temperature (°C)
Critical for Legionella proliferation (optimal 37°C). ASHRAE 188-2021 Legionella standard.
Ref: CDC Water Management Program 2021; ASHRAE 188-2021
Critical for Legionella proliferation (optimal 37°C). ASHRAE 188-2021 Legionella standard.
Ref: CDC Water Management Program 2021; ASHRAE 188-2021
Relative Humidity (%)
Modulates surface moisture and aerosol survival. ASHRAE 170 §6.4 recommends 30-60% RH.
Ref: EPA Aerosol Survival Studies 2022; ASHRAE 170-2021 §6.4
Modulates surface moisture and aerosol survival. ASHRAE 170 §6.4 recommends 30-60% RH.
Ref: EPA Aerosol Survival Studies 2022; ASHRAE 170-2021 §6.4
Initial Surface Load (units/m²)
Baseline contamination level from initial swab data or historical averages.
Ref: CDC 2023 Surface Sampling
Baseline contamination level from initial swab data or historical averages.
Ref: CDC 2023 Surface Sampling
Initial Hotspots
Number of localized high-load zones seeded with Gaussian distribution.
Ref: CDC Environmental Sampling Protocols
Number of localized high-load zones seeded with Gaussian distribution.
Ref: CDC Environmental Sampling Protocols
Water Contamination Index
Relative microbial loading in water systems feeding continuous aerosol shedding.
Ref: CDC Legionella Guidance 2021
Relative microbial loading in water systems feeding continuous aerosol shedding.
Ref: CDC Legionella Guidance 2021
Human Traffic (visits/hr)
Rate of human movement contributing to mechanical spread and shedding.
Ref: WHO Hand Hygiene & Traffic Studies 2023
Rate of human movement contributing to mechanical spread and shedding.
Ref: WHO Hand Hygiene & Traffic Studies 2023
Ventilation (ACH)
Core decay term. HVAC integration: effective decay += vent × 0.18 × (1 + 0.004 × humidity). ASHRAE 170 minimums enforced per layout.
Ref: ASHRAE 170-2021 Table 7-1; CDC Guidelines 2023
Core decay term. HVAC integration: effective decay += vent × 0.18 × (1 + 0.004 × humidity). ASHRAE 170 minimums enforced per layout.
Ref: ASHRAE 170-2021 Table 7-1; CDC Guidelines 2023
HEPA Filtration Efficiency (%)
Percentage of airborne particles removed (99% = MERV-17+ standard).
Ref: EPA HEPA Performance Standards
Percentage of airborne particles removed (99% = MERV-17+ standard).
Ref: EPA HEPA Performance Standards
Ozone Mitigation (ppb)
Oxidative gas concentration for broad-spectrum surface/air disinfection.
Ref: EPA Ozone Disinfection Guidance
Oxidative gas concentration for broad-spectrum surface/air disinfection.
Ref: EPA Ozone Disinfection Guidance
Chlorine Residual (ppm)
Free chlorine in water systems. Strong oxidizer; effectiveness reduced inside biofilm.
Ref: EPA Chlorine Guidance 2022
Free chlorine in water systems. Strong oxidizer; effectiveness reduced inside biofilm.
Ref: EPA Chlorine Guidance 2022
UV-C Intensity (µW/cm²)
Germicidal ultraviolet intensity at 254 nm. Dose-dependent inactivation.
Ref: CDC UV-C Disinfection 2023
Germicidal ultraviolet intensity at 254 nm. Dose-dependent inactivation.
Ref: CDC UV-C Disinfection 2023
UV-C Duty Cycle (%)
Percentage of time UV lamps are active.
Ref: ASHRAE UVGI Guidelines
Percentage of time UV lamps are active.
Ref: ASHRAE UVGI Guidelines
Surface Porosity Index (%)
Material porosity level (higher values protect microbes in micro-crevices).
Ref: CDC Surface Material Studies
Material porosity level (higher values protect microbes in micro-crevices).
Ref: CDC Surface Material Studies
Hours Since Last Clean
Time elapsed since last disinfection. Directly reduces clean_factor.
Ref: WHO Cleaning & Disinfection Protocols
Time elapsed since last disinfection. Directly reduces clean_factor.
Ref: WHO Cleaning & Disinfection Protocols
Duration (hours)
Forecast horizon for the entire simulation run.
Ref: Internal PathoSim validation
Forecast horizon for the entire simulation run.
Ref: Internal PathoSim validation
2. Enhanced 3D Airflow Modeling, HVAC Integration, ASHRAE 170 Compliance & Biofilm Formation Mechanisms
Airflow settling velocity: floor = 0.009 × airborne × layoutFactor
HVAC decay: airDecay += vent × 0.18 × (1 + 0.004 × humidity) + HEPA × 0.32
ASHRAE 170 compliance: ER ≥12 ACH, Waiting Room ≥6 ACH, ICU negative pressure verified by directional deposition.
Biofilm Formation Mechanisms (Miller & Bassler 2001; Waters & Bassler 2005):
Quorum sensing accelerates growth when avgLoad > 30 (factor = 1 + 0.0018 × (avgLoad-30)).
Extracellular matrix production: B(t) = min(1.0, 0.012 × t + 0.003 × avgLoad) reduces disinfectant efficacy by 48% at maturity.
Porosity & surface type modulate attachment per CDC Surface Material Studies.
HVAC decay: airDecay += vent × 0.18 × (1 + 0.004 × humidity) + HEPA × 0.32
ASHRAE 170 compliance: ER ≥12 ACH, Waiting Room ≥6 ACH, ICU negative pressure verified by directional deposition.
Biofilm Formation Mechanisms (Miller & Bassler 2001; Waters & Bassler 2005):
Quorum sensing accelerates growth when avgLoad > 30 (factor = 1 + 0.0018 × (avgLoad-30)).
Extracellular matrix production: B(t) = min(1.0, 0.012 × t + 0.003 × avgLoad) reduces disinfectant efficacy by 48% at maturity.
Porosity & surface type modulate attachment per CDC Surface Material Studies.
3. Pathogen Growth Models + Biofilm + Quorum Sensing
g_p = base_p × temp_factor × humidity_factor × water_factor × quorumFactor
quorumFactor = 1 + 0.0018 × (avgLoad - 30) (Miller & Bassler 2001)
B(t) = min(1.0, 0.012 × t + 0.003 × avgLoad)
decay_reduction = 1 - 0.48 × B(t)
HVAC-adjusted finalGrowth *= surfaceTrafficMultiplier
quorumFactor = 1 + 0.0018 × (avgLoad - 30) (Miller & Bassler 2001)
B(t) = min(1.0, 0.012 × t + 0.003 × avgLoad)
decay_reduction = 1 - 0.48 × B(t)
HVAC-adjusted finalGrowth *= surfaceTrafficMultiplier
4. Room-Type Specific Algorithms (Revised & ASHRAE-Aligned)
Emergency Room: layoutFactor = 1.35 (high floor traffic + gravity settling). ASHRAE 170 requires ≥12 ACH.
Waiting Room: layoutFactor = 1.15 (uniform airborne spread across all surfaces). ASHRAE 170 minimum 6 ACH.
ICU: layoutFactor = 1.3 (negative pressure increases floor load).
Operating Room: layoutFactor = 0.85 (positive pressure boosts ceiling deposition).
Standard Patient Room: layoutFactor = 1.0 (balanced).
PathoSim Detailed Summary Report –