Plan Review of a Hazardous (Classified) Location Storage Room
Plans for a new paint storage room show a Class I, Division 2 location because of flammable liquid storage. The plans specify general-purpose fluorescent luminaires mounted on the ceiling, standard snap switches inside the room at the door, and a convenience receptacle on the interior wall. The designer notes that the room is ventilated and that the quantities stored are below the threshold that would make it Division 1. The plan reviewer must determine whether the proposed electrical equipment and wiring methods are acceptable for the classification shown, and whether the classification itself is adequately documented.
1. Are the proposed luminaires, switches, and receptacle acceptable in the Class I, Division 2 room as shown? Explain the governing principle.
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No. In a Class I, Division 2 location, electrical equipment must be approved for the location and must be of a type that is not a source of ignition under normal conditions. General-purpose fluorescent luminaires, standard snap switches, and a standard convenience receptacle are not acceptable unless specifically approved for the classified location.
Governing principle: equipment in classified locations must be listed/approved for the class, division (or zone), and group, and wiring methods must be those permitted for the location. The designer's ventilation argument does not change the classification unless the ventilation is engineered and documented to maintain the area below the flammable threshold-an analysis the plans do not include. The reviewer should require:
- Luminaires approved for Class I, Division 2 (or relocated outside the classified area).
- Switches located outside the classified area or approved for it.
- Receptacles approved for the location, or elimination of the interior receptacle.
- Wiring methods suitable for the classified location.
2. What documentation should the reviewer require to accept the Division 2 classification, and what is the reviewer's action if it is not provided?
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The reviewer should require a documented area classification based on the quantities and properties of the stored liquids, the ventilation design, and the applicable classification standard, prepared or endorsed by a qualified person. The documentation should identify the class, division/zone, group, and the boundaries of the classified area, including any unclassified zones.
If the documentation is not provided, the reviewer should not accept the designer's assertion. The proper action is to withhold approval and issue a comment requiring the area classification documentation. The reviewer may also require that equipment be approved for the more stringent classification if the documentation is ambiguous, because the burden is on the designer to demonstrate the classification, not on the reviewer to assume it.