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IEC PAS 63166: Electrical Apparatus for Explosive Gas Atmospheres — Requirements for Portable Electronic Devices
Safety and design requirements for portable electronic equipment used in Zone 1 and Zone 2 explosive gas environments
Scope and Regulatory Context
The widespread adoption of smartphones, tablets, handheld terminals, wearable computers, and IoT-enabled portable devices has created an unprecedented challenge for industries operating in explosive gas atmospheres — oil and gas refineries, chemical plants, pharmaceutical facilities, grain handling, and mining operations. These environments, classified as Zone 1 (explosive gas likely to occur in normal operation) or Zone 2 (explosive gas unlikely but possible for short periods), require electrical apparatus that cannot ignite the surrounding atmosphere. IEC PAS 63166 addresses this gap by defining specific requirements for portable electronic devices intended for use in explosive gas atmospheres.
IEC PAS 63166 complements the existing IEC 60079 series (explosive atmospheres) by focusing on the unique challenges of portable, battery-powered electronic devices — including wireless connectivity, touchscreen interfaces, hot-swappable batteries, and multi-function sensors — that are not fully covered by traditional Ex equipment standards.
The PAS recognizes that portable electronic devices differ fundamentally from fixed or installed Ex equipment in several critical aspects: they are subject to frequent handling and dropping, they operate from rechargeable batteries that store significant energy, they incorporate multiple wireless transmitters (cellular, Wi-Fi, Bluetooth, NFC), and they are often used in varying orientations and environmental conditions. Each of these characteristics introduces potential ignition sources that must be rigorously assessed and controlled.
| Ignition Source | Relevant Device Feature | IEC PAS 63166 Requirement | Assessment Method |
|---|---|---|---|
| Hot surfaces | Processor, battery, LED flash | Max surface temperature < 80% of gas auto-ignition temperature | Thermal imaging + thermocouple measurement under max load |
| Electrical sparks | Connectors, switches, battery contacts | Creepage distances per IEC 60079-11, peak voltage < 12 V in Zone 1 | Dielectric strength test + gap measurement |
| Electrostatic discharge | Touchscreen, plastic enclosure, display | Surface resistance < 1 GΩ or ESD protective coating | Surface resistivity measurement (IEC 60079-0) |
| Radio frequency EMI | Wi-Fi, Bluetooth, cellular (2G/3G/4G/5G) | Max transmit power ≤ 100 mW ERP for Zone 1 | Spectrum analyzer measurement + spark test apparatus |
| Mechanical impact/friction | Drop protection, enclosure materials | Impact test at 2.0 m onto steel (no sparks, no ignition) | Drop test + light alloy composition analysis (Mg+Ti < 7.5%) |
| Battery failure | Li-ion/Li-polymer internal battery | Battery management system with redundant overtemperature and overcurrent protection | Thermal runaway test (forced short circuit + overcharge) |
Design Requirements and Type of Protection
IEC PAS 63166 specifies three types of protection that can be applied to portable electronic devices: intrinsic safety “ib” (suitable for Zone 1, limits both electrical and thermal energy to levels below the minimum ignition energy of the target gas), intrinsic safety “ic” (suitable for Zone 2, with less restrictive requirements than “ib”), and encapsulation “m” combined with limited energy circuits for applications where intrinsic safety alone cannot meet functional requirements. The choice of protection type involves trade-offs between safety integrity, device functionality, and cost.
A critical design constraint for intrinsically safe portable devices is the energy storage limitation. For “ib” rating, the available energy in the battery must be limited such that even under fault conditions (three countable faults per IEC 60079-11), the spark energy at any accessible point does not exceed 20 µJ for hydrogen (Group IIC) or 80 µJ for propane (Group IIA). This typically requires a battery capacity of less than 4 Wh for IIC applications — severely constraining device run time and feature set.
The PAS provides detailed guidance on battery pack design for Ex-rated portable devices, which is arguably the most challenging engineering aspect. Requirements include: redundant temperature monitoring (at least two independent NTC thermistors), individual cell voltage monitoring for multi-cell packs, current limiting at the cell level (using PTC devices or equivalent), and a gas-tight enclosure rated at IP67 minimum. The battery management system (BMS) must be designed to IEC 61508 SIL 2 capability, with fault reaction time less than 100 ms for overcurrent events and less than 1 second for overtemperature events.
| Protection Type | Applicable Zone | Energy Limitation | Enclosure Requirement | Typical Battery Limit | RF Power Limit |
|---|---|---|---|---|---|
| Ex ib IIC | Zone 1, Zone 2 | 20 µJ (IIC) / 80 µJ (IIB) | IP54 minimum | ≤ 4 Wh | ≤ 100 mW ERP |
| Ex ic IIC | Zone 2 only | 50 µJ (IIC) / 160 µJ (IIB) | IP54 minimum | ≤ 10 Wh | ≤ 500 mW ERP |
| Ex m + limited energy | Zone 1, Zone 2 | Encapsulation limits access; energy limits on external I/O | IP67 (encapsulation) | ≤ 20 Wh | ≤ 1 W ERP |
| Ex nA (non-sparking) | Zone 2 only | No arc/spark under normal operation | IP54 minimum | ≤ 30 Wh | ≤ 2 W ERP |
Wireless Communication and Ignition Risk
One of the most technically complex aspects addressed by IEC PAS 63166 is the assessment of ignition risk from wireless transmitters integrated into portable devices. Radio frequency (RF) energy can cause ignition through two mechanisms: direct sparking (where an RF arc forms between conductors in the presence of a flammable gas mixture) and induced currents (where the RF field induces sufficient current in nearby conductors to cause sparking). The PAS specifies test methods using a standard spark test apparatus (IEC 60079-11 Annex A) to determine the maximum safe transmit power for each wireless technology and frequency band.
From an engineering perspective, the document provides valuable data on RF ignition thresholds. For example, at 2.4 GHz (Wi-Fi/Bluetooth), the minimum ignition power in a 4.2% methane-air mixture is approximately 3.5 W — well above the typical 100 mW output of portable devices. However, at lower frequencies (e.g., 433 MHz ISM band), the ignition threshold drops to approximately 500 mW due to more efficient spark coupling. For cellular transmitters (700 MHz–2.1 GHz) with peak transmit power up to 200 mW, the PAS requires additional analysis of the duty cycle and modulation scheme, since pulsed RF (TDMA, GSM) has been shown to ignite gas mixtures at lower average power levels than continuous-wave transmission.
A practical engineering guideline derived from IEC PAS 63166 testing: for portable devices intended for Zone 1 gas environments, Wi-Fi and Bluetooth transmitters operating at ≤100 mW ERP can be used without additional interlock or gas detection, provided that the antenna is located at least 50 mm from any uninsulated conductor and the RF output is disabled during battery charging to eliminate the combined risk of AC power arc + RF arc.
Frequently Asked Questions
Q1: Can a standard consumer smartphone be certified for use in Zone 2 gas environments?
In most cases, no. Consumer smartphones typically do not meet the surface temperature limits, battery safety requirements, or ESD protection levels specified in IEC PAS 63166. However, some manufacturers offer Ex-rated “ruggedized” models that incorporate the necessary protective measures. Retrofitting a consumer device is generally not feasible due to the extensive modifications required in battery management, enclosure sealing, and wireless power control.
In most cases, no. Consumer smartphones typically do not meet the surface temperature limits, battery safety requirements, or ESD protection levels specified in IEC PAS 63166. However, some manufacturers offer Ex-rated “ruggedized” models that incorporate the necessary protective measures. Retrofitting a consumer device is generally not feasible due to the extensive modifications required in battery management, enclosure sealing, and wireless power control.
Q2: What is the difference between “Ex” certification and “ATEX” certification for portable devices?
Ex certification (IECEx Scheme) is the international system based on IEC standards, while ATEX certification is the European Union system based on EN versions of the same IEC standards. IEC PAS 63166 aligns with both systems. A device certified under IECEx is typically accepted in ATEX jurisdictions (and vice versa) through bilateral agreements, though some national variations exist.
Ex certification (IECEx Scheme) is the international system based on IEC standards, while ATEX certification is the European Union system based on EN versions of the same IEC standards. IEC PAS 63166 aligns with both systems. A device certified under IECEx is typically accepted in ATEX jurisdictions (and vice versa) through bilateral agreements, though some national variations exist.
Q3: How does the standard address the risk of device damage from dropping (common in field operations)?
IEC PAS 63166 specifies a comprehensive mechanical test regime: drop test from 2.0 m onto a steel plate in six orientations (flat, edge, corner), followed by visual inspection, functional test, and repeat of all ignition protection tests. For devices with Ex ib protection, the drop test must not result in any internal short circuit that could defeat the safety barriers. The enclosure must also pass a 2 J impact test (IEC 60079-0) at the most vulnerable points.
IEC PAS 63166 specifies a comprehensive mechanical test regime: drop test from 2.0 m onto a steel plate in six orientations (flat, edge, corner), followed by visual inspection, functional test, and repeat of all ignition protection tests. For devices with Ex ib protection, the drop test must not result in any internal short circuit that could defeat the safety barriers. The enclosure must also pass a 2 J impact test (IEC 60079-0) at the most vulnerable points.
Q4: Are there special requirements for devices that include both Ex-rated and non-Ex-rated functions?
Yes. The PAS introduces the concept of “functional segregation” — the device must clearly indicate which features are safe to use in the hazardous area and which must be disabled. For example, the camera and barcode scanner may be Ex-rated, while the high-power LED flashlight must be locked out when the device detects (via a gas sensor or zone input) that it is in a hazardous location.
Yes. The PAS introduces the concept of “functional segregation” — the device must clearly indicate which features are safe to use in the hazardous area and which must be disabled. For example, the camera and barcode scanner may be Ex-rated, while the high-power LED flashlight must be locked out when the device detects (via a gas sensor or zone input) that it is in a hazardous location.
