ATEX/IECEx Zone Classification Helper - Design Calculators

ATEX / IECEx Zone Classification Helper (IEC 60079-10-1)

This industrial-grade calculator performs a Quantitative Risk Assessment for Hazardous Area Classification. It calculates the Mass Release Rate ($W_g$) and Hypothetical Volume ($V_z$) to scientifically determine the Zone (0, 1, 2) or Division extent based on IEC 60079-10-1:2020 methodology.

1. Fluid Properties & Process Data

Gas / Vapor Selection

Molecular Weight ($M$) [g/mol]

Lower Explosive Limit (LEL) [vol %]

Specific Heat Ratio ($k = C_p/C_v$)

System Pressure ($P$) [bar gauge]

Temperature ($T$) [°C]

Auto-Ignition Temp (AIT) [°C]

Gas Group (IEC/NEC)

2. Leak Source & Coefficients

Leak Cross-Section ($A$) [mm²]

Grade of Release

Discharge Coefficient ($C_d$)

3. Ventilation Parameters

Ventilation Velocity ($u_w$) [m/s]

Ventilation Availability

Safety Factor ($k$)

Classification Summary

Parameter	Result

Professional Insights: Quantitative Assessment (IEC 60079-10-1)

Hypothetical Volume ($V_z$) Concept

The core of modern IEC classification is determining the size of the gas cloud. $V_z$ represents the volume where the mean concentration of gas exceeds 25% or 50% of the LEL.

Negligible Extent ($V_z < 0.1 \text{ m}^3$): If the calculated cloud is tiny, a Zone 2 area might be declared "Zone 2 NE" (Negligible Extent) or even Safe, provided ventilation is high.
Significant Extent: If $V_z$ is large, the Zone must extend to cover the hazard.

Dilution & Quality Factor ($f$)

The standard defines a Quality Factor $f$ based on ventilation efficiency:

$f=1$ (Good): Ventilation is present virtually continuously.
$f=3$ (Fair): Ventilation is present during normal operation.
$f=5$ (Poor): Ventilation may be interrupted.

This factor directly multiplies the Hypothetical Volume ($V_z$), meaning poor ventilation increases the hazardous zone size by 5x.

Temperature Class Selection

The T-Class is determined purely by the chemical's Auto-Ignition Temperature (AIT). Equipment surface temperature must always be lower than the AIT.

T1 (450°C) > T2 (300°C) > T3 (200°C) > T4 (135°C) > T5 (100°C) > T6 (85°C). (T6 is the safest/coolest equipment rating).