Ex n is the minimum protection concept for Zone 2 areas. It provides enhanced protection against ignition in normal operation but does not achieve the fault tolerance of Ex d or Ex e. This unit covers the four Ex n subtypes (nA, nC, nR, nL), Zone 2 application limits, and the key differences from Ex e.
Learning Objectives
State the EPL for Ex n equipment and confirm it is Zone 2 only
Distinguish between Ex nA, nC, nR, and nL subtypes
Explain why Ex n cannot be used in Zone 0 or Zone 1
State cable gland and sealing requirements for Ex n and Ex nR entries
Identify typical Ex n inspection faults
Ex n Protection Concept
Ex n (Type N) provides a level of protection designed for Zone 2 only — where an explosive atmosphere is not expected in normal operation but may occur briefly. The design prevents ignition sources under normal operation but does not provide the fault tolerance required for Zone 0 or Zone 1.
Equipment Protection Level: Gc — Zone 2 only. ATEX Category 3. Standard IEC 60079-15. Similar in concept to Ex e but with less stringent requirements — no de-rating of terminals, lower impact strength requirements.
⚠ Zone 2 Only — Never Zone 0 or Zone 1
EPL Gc equipment must not be installed in Zone 0 or Zone 1 regardless of gas group or T-class compliance. Installing Ex n equipment in Zone 1 is a Category X deficiency requiring immediate withdrawal.
Ex n Subtypes
Subtype
Description
Example
nA — Non-Sparking
Components do not arc or spark in normal operation
General Zone 2 luminaires, JBs, motors
nC — Protected Sparking
Sparking contacts enclosed in sealed or hermetically sealed device. (Now equivalent to Ex mc)
Reed switches, hermetically sealed contacts
nR — Restricted Breathing
Enclosure restricts gas ingress rate so flammable concentration cannot build during brief Zone 2 event
Tightly gasketed enclosures with defined leak rate
nL — Energy Limited
Circuit energy too low to cause ignition even if spark occurs. May be used in Ex ic circuits
Low energy control circuits
Cable Glands and Installation
From 2007: only certified cable glands meeting IEC 60079-0 may be used with Ex n enclosures. Certified Ex e glands are suitable for Ex n use. For Ex nR equipment, the cable entry must maintain the restricted-breathing property — certified Ex d/Ex e/Ex nR glands are required where the manufacturer specifies a restricted-breathing seal. A suitable sealing washer must be fitted between gland and enclosure for Ex nR entries.
Unused entries must be sealed with certified blanking plugs maintaining at least IP54.
Quick Check — 5 Questions
Test key concepts from this unit before moving on.
Q1Summary
Ex nA equipment is found installed in a Zone 1 area. What deficiency category?
Ex nA is EPL Gc — Zone 2 only. Zone 1 requires minimum EPL Gb. This is a Category X deficiency identifiable from the nameplate at Visual inspection grade. The equipment must be withdrawn from service immediately and replaced with Zone 1-rated equipment.Ref: IEC 60079-17 — Zone Suitability
Q2Summary
What is the key difference between Ex nA and Ex nR?
Ex nA (non-sparking) equipment does not produce arcs or sparks in normal operation. Ex nR (restricted breathing) controls the rate of gas ingress into the enclosure so that a flammable concentration cannot build to ignitable levels during the brief duration of a Zone 2 gas release event.Ref: IEC 60079-15 — Ex n Subtypes
Q3Summary
Can Ex e certified glands be used on Ex n enclosures?
Certified Ex e glands meet the requirements for use with Ex n enclosures under current IEC 60079-0. From 2007, only certified glands (Ex e, Ex d/e, or Ex n types) may be used with Ex n equipment.Ref: IEC 60079-15 / IEC 60079-0
Q4Summary
A Zone 2 area is classified IIB, T4. Equipment marked "Ex nA IIA T4 Gc" is available. Is it suitable?
The gas group is wrong. IIA equipment covers only IIA atmospheres. The area is IIB — IIB gases have a narrower MESG and lower MIC ratio than IIA. Equipment must be rated for at least the area gas group. This is a Category X deficiency identifiable at Visual inspection grade.Ref: IEC 60079-0 — Gas Group Selection
Q5Summary
What minimum IP rating is required for an Ex n enclosure containing bare live parts?
Ex n enclosures containing bare live parts require IP54. Ex n enclosures containing only insulated live parts may use IP44. This differs from Ex e (minimum IP54 in all cases). The IP rating must be maintained throughout service life — damaged gaskets are Category A deficiencies.Ref: IEC 60079-15 — IP Requirements
EX Academy — independent CompEx-style preparation. Not official CompEx course materials.
Unit 5 · Ex01 & Ex02 · Full Manual
Type of Protection — Ex n
Ex n is the minimum protection concept for Zone 2 areas. It provides enhanced protection against ignition in normal operation but does not achieve the fault tolerance of Ex d or Ex e. This unit covers the four Ex n subtypes (nA, nC, nR, nL), Zone 2 application limits, and the key differences from Ex e.
Learning Objectives
State the EPL for Ex n equipment and confirm it is Zone 2 only
Distinguish between Ex nA, nC, nR, and nL subtypes
Explain why Ex n cannot be used in Zone 0 or Zone 1
State cable gland and sealing requirements for Ex n and Ex nR entries
Identify typical Ex n inspection faults
5.2 Ex n Protection Concept
Type N protection is designed specifically for Zone 2 — where explosive atmospheres are not expected in normal operation but may occur briefly. The design prevents ignition sources from occurring in normal operation but does not need to provide the fault tolerance of Ex d or Ex e.
EPL Gc (Category 3). Zone 2 only. Standard: IEC 60079-15. Similar to Ex e in principle but with less stringent construction requirements — terminals do not need to be de-rated to 50%, impact requirements are lower, and the overall design is simpler and more economical for Zone 2 applications.
⚠ Zone 2 ONLY — Never Zone 0 or Zone 1
All Ex n subtypes are EPL Gc. They provide protection adequate for Zone 2 — where normal operation is gas-free. Zone 1 has explosive atmospheres that occur occasionally in normal operation — EPL Gc does not provide the necessary fault tolerance for this scenario. Installing Ex n (nA, nC, nR, nL) equipment in Zone 1 or Zone 0 is a Category X deficiency.
5.3 Ex n Subtypes
Ex nA — Non-Sparking
Equipment constructed so that components do not arc, spark, or produce hot surfaces capable of ignition in normal operation. The most common Ex n type. Used for Zone 2 general equipment: luminaires, junction boxes, control stations, induction motors. EPL Gc.
Ex nC — Protected Sparking (now Ex mc)
Sparking or hot components enclosed within a sealed or hermetically sealed device preventing the spark from contacting the external atmosphere. The protection technique for Ex nC has now been absorbed into IEC 60079-18 as encapsulation "mc". Ex nC ≡ Ex mc. EPL Gc. Voltage and current limitations: maximum 690V, 16A for enclosed-break devices. Free internal volume of the Ex d sub-enclosure must not exceed 20cm³.
Ex nR — Restricted Breathing
The enclosure is designed with sufficiently tight gasketing that the rate of gas ingress is controlled. The controlled ingress rate means that a flammable concentration cannot build up inside the enclosure during the brief duration of a Zone 2 release event. Special Ex nR or Ex d/Ex e/nR certified glands are required to maintain the restricted breathing property at cable entries. A sealing washer must be fitted between the gland and the enclosure.
Ex nL — Energy Limited
Circuit energy limited to below the ignition threshold — similar to intrinsic safety but to a lower standard. Equipment to Ex nL protection may be used in Ex ic (intrinsically safe level c) circuits. EPL Gc.
5.5 Design and Construction
Principal design features for Ex n (nA) compared to Ex e:
Feature
Ex e
Ex nA
Minimum IP (with bare live parts)
IP54
IP54
Minimum IP (with only insulated parts)
IP54
IP44
Terminal de-rating
50% of standard rating
Less stringent — manufacturer data applies
Terminal locking devices
Mandatory
Required
Sparking components inside
Not permitted without own Ex d enclosure
nC or nR methods required
Impact strength requirement
Higher
Standard to test levels
5.6 Cable Glands for Ex n
From 2007, only certified cable glands meeting IEC 60079-0 may be used with Ex n enclosures. Certified Ex e glands are suitable for Ex n use. For Ex nR equipment, the gland must maintain the restricted-breathing properties of the enclosure — certified Ex d/Ex e/Ex nR glands are specified where the manufacturer requires restricted-breathing seals. Consult the equipment documentation to confirm whether standard IP washers or restricted-breathing seals are required at each entry.
Unit 5 Knowledge Check — 10 Questions
CompEx-style questions covering the full unit content.
Q1Unit {num}
Ex nR equipment uses restricted breathing enclosure design. What special requirement applies to cable gland selection?
Ex nR equipment relies on controlled gas ingress rate for its protection. The cable entry must maintain this property. Manufacturer documentation specifies whether restricted-breathing seals (supplied by the equipment manufacturer) or normal IP washers may be used with the specific gland types listed.Ref: IEC 60079-15 — Ex nR Cable Entries
Q2Unit {num}
What does "Ex nC" mean in modern Ex marking standards?
Ex nC covers sparking or hot components enclosed within a sealed or hermetically sealed device (enclosed-break device, hermetically sealed reed switch). This technique has now been incorporated into IEC 60079-18 as encapsulation level mc. Ex nC ≡ Ex mc.Ref: IEC 60079-15 / IEC 60079-18
Q3Unit {num}
Which luminaire installation is correct for a Zone 2, IIB, T3 area?
Zone 2, IIB, T3. Minimum EPL Gc. IIB rated equipment (covers IIA and IIB). T3 (200°C max surface) meets T3 requirement. Ex nA IIB T3 Gc is the minimum compliant selection. IIC covers IIB (also acceptable), and Ex d (Gb) in Zone 2 is over-specified but compliant. IIA would be wrong for an IIB area.Ref: IEC 60079-0 — Equipment Selection for Zone 2
Q4Unit {num}
An Ex nR enclosure is found with a standard rubber IP washer fitted at the cable entry where the manufacturer specifies a restricted-breathing sealing washer. What is the deficiency?
The restricted-breathing property of Ex nR depends on controlled gas ingress through all sealing points including cable entries. Using a standard IP washer instead of the manufacturer-specified restricted-breathing seal could allow higher gas ingress rates than the design accounts for. Category A deficiency — correct before return to service.Ref: IEC 60079-15 / IEC 60079-17
Q5Unit {num}
What is the maximum free internal volume of an enclosed-break device (Ex nC) sub-enclosure for a sparking contact?
The maximum free internal volume for an enclosed-break Ex nC sub-enclosure is 20cm³. This sub-enclosure (which effectively works as a small Ex d enclosure) is also limited to maximum 690V and 16A. Hermetically sealed devices (welded glass, soldering, brazing) have no volume limit as no gas can enter.Ref: IEC 60079-15 — Ex nC Enclosed-Break Device
Q6Unit {num}
Ex n luminaires are being installed in a Zone 2 outdoor area rated IIC T4. The available luminaires are marked "Ex nA IIB T4 Gc". Why are these NOT suitable?
IIC atmospheres include hydrogen and acetylene — the most easily ignited gas group (MESG ≤0.5mm, MIE ~19μJ for hydrogen). IIB equipment (MESG 0.5–0.9mm) does not cover IIC. Category X deficiency — the luminaires must not be installed. IIC rated Ex n equipment is required.Ref: IEC 60079-0 — Gas Group Selection
Q7Unit {num}
A Zone 2 motor is marked "Ex nA IIB T3 Gc". The nameplate shows no tE time. Is this correct for an Ex n motor?
tE time is a specific requirement of Ex e (increased safety) motors where the overload relay trip time within tE is a safety-critical function. Ex nA (Type N non-sparking) motors do not have the same tE time requirement — their thermal performance is controlled by design but without the mandatory tE marking and relay verification that applies to Ex e.Ref: IEC 60079-15 — Ex n vs Ex e Motor Requirements
Q8Unit {num}
After a Zone 2 area is re-classified as Zone 1 due to a process change, what action is required for existing Ex n equipment?
Re-classifying an area from Zone 2 to Zone 1 means the minimum EPL changes from Gc to Gb. All EPL Gc equipment (all Ex n types) is no longer suitable and must be replaced with EPL Gb equipment (Ex d, Ex e, Ex ib, etc.) before the area is re-energised. This is a major project requiring a full equipment schedule review.Ref: IEC 60079-0 — Zone Re-classification
Q9Unit {num}
What does the "L" in Ex nL signify?
Ex nL denotes energy-limited protection — the electrical energy in the circuit is limited to below the minimum ignition energy of the surrounding atmosphere. This is similar in principle to intrinsic safety (Ex i) but to a lower protection standard. Ex nL equipment may be used in Ex ic circuits.Ref: IEC 60079-15 — Ex nL Definition
Q10Unit {num}
An Ex nA IIC T4 Gc junction box is installed in a Zone 2, IIB, T4 area. Is this compliant?
IIC rated equipment covers all Group II gas subdivisions including IIA, IIB, and IIC. Using IIC in an IIB area is acceptable — it is over-specified for gas group but compliant. T4 meets the T4 area requirement. EPL Gc is Zone 2 suitable. The installation is compliant. Using a more expensive IIC enclosure in an IIB area is technically acceptable and sometimes done to simplify spare-part management.Ref: IEC 60079-0 — Gas Group Upward Compatibility