What is a Hazardous Location?
What is an explosive atmosphere?
Key Components of an Explosive Atmosphere
Class/Division System Overview
Classes and Divisions Classification
- Group A: Acetylene (highly explosive and volatile).
- Group B: Hydrogen or gases with similar properties (e.g., butadiene, ethylene oxide).
- Group C: Ethylene or gases with similar explosive characteristics.
- Group D: Methane, propane, butane, gasoline, and similar gases (less volatile than Group A, B, or C).
- Group E: Combustible metal dusts (e.g., aluminum, magnesium).
- Group F: Carbonaceous dusts (e.g., coal, charcoal).
- Group G: Combustible dusts from grain, flour, plastics, chemicals (e.g., grain dust, flour dust).
Summary of Classes, Divisions, and Groups
Class
Division 1 (D1)
Division 2 (D2)
Group Examples
Class 1 (Gases)
Flammable gases or vapors present under normal conditions.
Gases or vapors only present during abnormal conditions.
A (Acetylene), B (Hydrogen), C (Ethylene), D (Propane, Methane)
Class 2 (Dusts)
Combustible dust is present under normal conditions.
Dust is present only under abnormal conditions.
E (Metal Dusts), F (Coal Dust), G (Grain, Flour)
Class 3 (Fibers)
Combustible fibers are present under normal conditions.
Fibers or flyings present under abnormal conditions.
Not divided into specific groups.
What is C1D2?
In short, Class 1 Division 2 (C1D2) refers to hazardous environments where flammable gases, vapors, or liquids are present only under abnormal conditions, such as equipment malfunctions or leaks. While these substances are typically absent during normal operations, equipment used in these locations must be designed to prevent ignition in the event of accidental exposure.
- Explosive Atmosphere Likelihood: The presence of flammable gases or vapors in C1D2 areas is infrequent and only occurs during abnormal conditions such as equipment leaks or accidental releases.
- Normal Operation: During normal operation, no hazardous atmosphere should be present. However, equipment must be capable of preventing ignition if a hazardous substance is released unexpectedly.
ATEX Directive Overview
The ATEX directive (short for Atmosphères Explosibles) is a European regulation designed to ensure safety in environments where there is a risk of explosions due to the presence of flammable gases, vapors, mists, or dusts. The directive covers both:
- ATEX 99/92/EC (also known as the ATEX Workplace Directive), which governs the safety of workers in explosive atmospheres.
- ATEX 2014/34/EU (also known as the ATEX Equipment Directive), which governs the design and certification of equipment used in explosive atmospheres.
ATEX Zones Classification
- Zone 0: An area where an explosive atmosphere is present continuously or for long periods (more than 1,000 hours per year).
- Zone 1: An area where an explosive atmosphere is likely to occur during normal operations (between 10 and 1,000 hours per year).
- Zone 2: An area where an explosive atmosphere is unlikely to occur during normal operation, and if it does, it will be infrequent and last for a short time (less than 10 hours per year).
- Zone 20: Explosive dust is present continuously or for long periods.
- Zone 21: Explosive dust is likely to occur occasionally during normal operations.
- Zone 22: Explosive dust is unlikely to occur during normal operation and will persist only for short periods.
What is ATEX Zone 2?
Zone 2 is considered one of the least hazardous of the three zones. While it’s possible for an explosive atmosphere to form in Zone 2, it happens infrequently and only under abnormal conditions like equipment leaks or failures.
- Explosive Atmosphere Likelihood: Flammable gases or vapors are only expected to be present for short durations and not under normal operating conditions.
- Equipment Requirements: Equipment used in Zone 2 must be designed to prevent ignition, but the standards are less stringent compared to those required for Zones 0 and 1. For instance, non-sparking equipment or equipment with low surface temperatures is often used. ATEX-certified equipment is labeled with the marking for Zone 2, ensuring that it is safe for use in such environments.
- Typical Industries: Zone 2 environments are common in industries such as oil and gas refineries, chemical processing plants, pharmaceutical manufacturing, and food processing facilities, where occasional leaks or emissions of flammable substances can occur.
Comparison Between Class 1 Division 2 (C1D2) and ATEX Zone 2
Feature
C1D2 (Class 1 Division 2)
ATEX Zone 2
Geographical Scope
North America (U.S. and Canada)
Europe (European Union, under ATEX directive)
Classification System
Class/Division System
Zone System
Likelihood of Hazard
Flammable gases or vapors present only under abnormal conditions (e.g., leaks, equipment failure)
Explosive atmosphere unlikely during normal operations, present only under abnormal conditions (e.g., brief malfunctions)
Regulatory Framework
Governed by NEC (National Electrical Code) and CEC (Canadian Electrical Code)
Governed by ATEX Directive 2014/34/EU
Equipment Requirements
Must avoid ignition sources (sparks, overheating). Explosion-proof not always required, but equipment must prevent ignition.
Category 3 equipment required; designed to prevent ignition in case of accidental exposure to explosive atmospheres.
Common Industries
Oil and gas, chemical processing, pharmaceuticals, fuel storage (North America)
Oil and gas, chemical plants, refineries, pharmaceuticals (Europe)
Certification Bodies
UL (Underwriters Laboratories), CSA (Canadian Standards Association)