A plain-English overview of Class I, Division 2 (C1D2) for remote heads—what the listing covers, where to locate the power unit, acceptable wiring methods, and how to document your plan so it passes inspection.
Last updated: October 2025
What C1D2 means (and why it matters)
Class I, Division 2 areas are locations where flammable gases or vapors are present only under abnormal conditions (leaks, maintenance, failure). Remote heads installed in these spaces must be specifically listed for C1D2, including temperature code and enclosure type as applicable. General-purpose or only “wet-location” heads are not enough.
For broader code context and AHJ expectations, see the remote head code requirements overview.
- Area classification refresher: C1D2 (gas/vapor under abnormal conditions) vs C1D1 (present in normal operation) vs unclassified areas outside the boundary.
- Gas groups & T-codes: Select heads with the correct gas group and T-code; ensure max surface temperature is safe for the process/ambient.
Power unit location (best practice)
- Prefer unclassified (safe) areas: Mount the remote-capable battery/inverter where it isn’t exposed to the classified atmosphere—simplifies listings, wiring methods, and maintenance.
- If the host must be in C1D2: Use a unit and accessories that are listed for C1D2, with proper enclosure type. Coordinate labels and documents with your AHJ.
- Distance to heads: Keep runs short; long home-runs increase voltage drop and complicate conductor sizing.
- Boundary planning: If the host is outside, show boundary seals and routing on your one-line.
Wiring methods & voltage choices
Conductors & fittings: Follow classified-location methods (sealing fittings where required, approved conduit/hubs, bonding/grounding). Mark polarity at every termination. For long runs or many heads, step up supply voltage and size conductors to control drop.
Choosing supply: compare options in 12V vs 24V for remote heads, then use the wire-gauge & distance tables to pick AWG and confirm one-way distances within your drop limit (often ~5%).
Head selection & environment
- Listing first: Head must be C1D2-listed (and T-code appropriate to gas group and ambient).
- Environment: Many hazardous spaces are also wet, dusty, or corrosive. If exposed to weather or washdown, pair C1D2 with wet-location/IP/NEMA rating—see outdoor IP65 spacing & aiming for mounting/aiming details.
- Compatibility: Verify head voltage/load match the host. For mixed families, consult a remote head compatibility matrix before ordering.
- Optics & aiming: Reduce glare with off-axis aims and suitable beam angles; avoid hot spots on shiny equipment or thresholds.
Labeling & documentation
- One-line diagram: Show head count, watts/head, conductor gauge, run lengths, boundary seals, and host location (classified vs unclassified).
- Listings packet: Include spec sheets showing C1D2 listing, T-code, enclosure/hub details for heads and any in-space power equipment.
- Voltage-drop math: Keep calculations and assumptions (ambient, design buffer, drop target). Cross-check AWG with the wire-gauge tables above.
- Test records: Monthly quick checks and annual 90-minute logs retained per local policy.
Inspection checklist
- Correct listing: Heads (and any in-space equipment) marked for C1D2; T-code appropriate to hazard.
- Wiring method: Approved fittings/seals used; polarity/grounds correct.
- Voltage drop: Conductors sized per run length; far head remains bright at end-of-discharge. See the tables above.
- Coverage: Aim/overlap to avoid dark bands at doors and along the path. If outdoors, apply IP65 spacing/aiming practices referenced above.
- Documentation: One-line, listings, and test logs on file; see the code overview earlier for AHJ expectations.
Fire Code quick references
Useful baselines for hazardous-location egress equipment (confirm with your AHJ):
FAQ
Can a wet-location remote head be used in C1D2?
No—“wet-location” alone isn’t sufficient. The head needs a C1D2 listing appropriate to the gas group and T-code.
Where should I put the remote-capable battery/inverter?
Prefer unclassified areas just outside the boundary. If the host must be in C1D2, use equipment listed for the area and document enclosures, seals, and T-code.
Do I need 24 V for multi-landing risers?
Not always, but 24 V reduces current and helps manage drop on long vertical runs. Compare 12V vs 24V and select AWG from the wire-gauge tables.
This article focuses on hazardous-location (C1D2) basics for remote heads. For fundamentals and step-by-step sizing, use the core remote head sizing & wiring guide (linked in the CTA).