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Class 1 Div 1 vs. Div 2 (C1D1 vs C1D2) Diagram

Hazardous Location Exit Signs – Class 1 Div 1 vs. Div 2 (C1D1 vs C1D2)

Installing exit signs in hazardous environments requires more than standard fixtures. If you’re deciding between Class I, Division 1 (C1D1) vs Class I, Division 2 (C1D2) exit signs, the difference comes down to how often flammable gas/vapor can be present: Div 1 can be present in normal operation; Div 2 is not normally present and typically appears only under abnormal conditions (leaks, maintenance, equipment failure).

In areas where flammable gases, vapors, dusts, or fibers are present, standard electrical equipment can become an ignition source. That’s why hazardous‑location exit signs use sealed housings and flame‑path designs to help prevent internal sparks from igniting the surrounding atmosphere. For compliant options, see our hazardous location (explosion‑proof) collection.

Last updated: February 2026

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Table of Contents

  1. What Are Hazardous‑Location Exit Signs?
  2. NEC Classification (Class • Division • Group)
  3. Where Class I Div 1 Exit Signs Are Required
  4. Where Class I Div 2 Exit Signs Are Used
  5. Div 1 vs Div 2 — At a Glance
  6. Nameplate & Listings (UL 844 • UL 924 • T‑Code • Ta)
  7. Enclosures & Environment (NEMA/IP, Corrosion, Temperature)
  8. Common Applications & Placement Tips

UL 924 • UL 844 • NEC 500–516 Educational Guide For Safety & Facilities Teams

Quick Picks

Pick Class & Division

  • Class I: Gas/Vapor (e.g., propane, hydrogen).
  • Div 1 (C1D1): Hazard can be present in normal operation (or frequently due to leaks/maintenance).
  • Div 2 (C1D2): Hazard is not normally present; typically appears under abnormal conditions (leaks, upsets, failures) or adjacent to Div 1.

Verify Listings

  • UL 844 marking (Class/Division/Group + temperature rating).
  • UL 924 for egress devices (EXIT visibility & transfer/runtime requirements).
  • Ta ambient range suitable for your space (T‑code applies at a stated ambient).

Install Right

  • Use listed sealing fittings & hubs as required.
  • Maintain gasket & flame‑path integrity (don’t damage or contaminate mating surfaces).
  • Log 30‑sec monthly & 90‑min annual tests (per site program/code requirements).

What Are Hazardous‑Location Exit Signs?

Often called explosion‑proof exit signs, these fixtures are engineered to contain internal arcs and flames so they don’t ignite surrounding gases or vapors. Selection starts with your area’s Class (hazard type), Division (likelihood), and Group (specific substance). Getting this right helps avoid red tags and protects people.

Primer: Class, Division & Group — Plain‑English Primer

NEC Classification (Class • Division • Group)

Class Groups (Examples)
Class I (Gases/Vapors): You may see Division gas groups (A–D) and/or Zone gas groups (IIA/IIB/IIC) depending on how the fixture is marked/listed and how the project is classified.
Zone-style examples: IIA (propane), IIB (ethylene), IIC (hydrogen/acetylene)
Class II (Dusts): E (metal), F (coal/carbon), G (grain/wood/flour)
Class III (Fibers): Ignitable fibers/flyings (no sub‑groups)

Tip: Many sites have drawings/specs that call out a specific system. Match what’s on your plans and confirm Division (1 or 2) plus the required T‑code and Ta ambient on the nameplate.

Where Class I Div 1 Exit Signs Are Required

Use Class I Div 1 (C1D1) exit signs where flammable gas/vapor can be present under normal operating conditions (or frequently). These signs often use heavier cast housings, flame paths, and gasketing to help contain ignition.

Typical Div 1 Areas:

  • Spray booths & solvent mixing rooms
  • Digester headspaces & pump skids handling live vapors
  • Offshore modules, refinery process units

Where Class I Div 2 Exit Signs Are Used

Class I Div 2 (C1D2) covers adjacent/abnormal‑occurrence areas where gases/vapors are not normally present but may appear during leaks, maintenance, or upsets. Equipment must still prevent ignition if a release occurs.

Div 1 vs Div 2 — At a Glance

Hazardous location exit signs comparison showing Class I Division 1 (C1D1) vs Class I Division 2 (C1D2) plus a nameplate checklist for UL 844, UL 924, Class/Div/Group, T-code, and Ta ambient.
C1D1 vs C1D2 at a glance, plus the nameplate checklist to verify before installation.

Criteria    Div 1 (C1D1)    Div 2 (C1D2)
Hazard presence   Normal / frequent   |   Abnormal / occasional
Typical areas   Process “hot zones”, areas where release can occur in normal ops   |   Adjacent / perimeter areas, where release is not expected in normal ops
Selection impact   More stringent construction/marking required   |   Still must be correctly listed/marked; may allow different listed designs
Cost/weight   Higher   |   Lower (model dependent)

Related: Class I Div 1 vs Div 2 — What Changes?

Nameplate & Listings (UL 844 • UL 924 • T‑Code • Ta)

  • UL 844: Confirms hazardous‑location construction. Nameplate should show the required Class/Division/Group (or Zone marking where applicable) plus temperature rating.
  • UL 924: Required for egress devices where specified (EXIT visibility, transfer to battery, ~90‑minute runtime requirements as applicable).
  • T‑code & Ta: T‑code applies at a stated ambient (Ta); ensure the label covers your hottest conditions.
  • Groups: Match the gas family shown on the plans/nameplate (some nameplates show Zone groups IIA/IIB/IIC; IIC is typically most stringent among those).
  • Commissioning tip: Photograph the nameplate(s) for closeout and AHJ walk‑throughs.

Temperature basics: T‑Codes for Explosion‑Proof Fixtures

Enclosures & Environment (NEMA/IP, Corrosion, Temperature)

  • NEMA/IP: Where washdown, rain, or salt spray exist, specify NEMA 4X / IP66 in addition to UL 844 (environmental sealing does not replace haz‑loc listing).
  • Materials/finish: Consider copper‑free aluminum or FRP housings, marine‑grade coatings, and stainless hardware where corrosion is a concern.
  • Cold/hot: Consider battery performance in cold areas; verify Ta for hot mezzanines or enclosures.
  • Wiring: Use listed explosion‑proof sealing fittings; keep flame‑path joints pristine and bolts torqued per spec.

Compare terms: Explosion‑Proof vs Wet‑Location vs Outdoor

Common Applications & Placement Tips

  • Doors & junctions: Place signs for sightlines around tanks and racks; verify visibility along the path.
  • High bays & long runs: Pair exit signs with hazardous‑location emergency lights (or remote heads) to meet floor levels along the path of egress.
  • Commissioning: Photograph nameplates; document 30‑sec and 90‑min tests for the AHJ.

How‑to: Installing Explosion‑Proof Lighting

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Compliance Reminder
Bottom line: Match Class/Division/Group and temperature rating to your area, confirm UL 844 and (for egress) UL 924, and maintain seals, gaskets, and torque so the rating is preserved.