OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 40 Utility Workers – Electrical

Explanation of Rules Referenced from the ECUC, Second Edition

Rule 4-018 Fire extinguishers

An employer must ensure that workers are trained in how to use approved fire extinguishing equipment on or in close proximity to energized electrical equipment. The fire extinguishing equipment must be in accordance with the requirements of the current Alberta Fire Code.

At the present time, the 1997 edition of the Alberta Fire Code applies. In particular, section 6.2.3.7 Extinguishers for Class C Fires specifies the requirements applicable to portable fire extinguishers:

(1) portable fire extinguishers for class C fires i.e. fires involving energized electrical equipment, must be provided in or near electrical equipment, and
(2) the portable fire extinguishers must be distributed according to the applicable requirements of table 6.2.3.3 or table 6.2.3.5 of the Alberta Fire Code.

Readers are referred to these tables for information describing the size, quantity, and distribution of fire extinguishers required for their specific circumstances.

The Alberta Fire Code refers readers to National Fire Protection Association (NFPA) Standard 10, Portable Fire Extinguishers. The following explanatory information is based on what is presented in Section E.5 of the NFPA Standard.

When the power to a piece of electrical equipment is cut off, the fire changes character to that of a Class A fire (i.e. a fire involving combustible materials such as wood, cloth and paper), a Class B fire (i.e. fire involving a flammable liquid or combustible liquid, fat or grease), or a combined Class A and B fire, depending on the nature of the burning electrical components and any material burning in the immediate vicinity.

Isolating and grounding electrical equipment eliminates the possibility of shock hazards to the fire extinguisher operator if the operator accidentally comes into physical contact with the equipment, or if the operator brings any conductive part of a fire extinguisher within arcing distance. Isolating and grounding also eliminates fault currents from prolonging the fire or from being a source of re-ignition.

Switches or circuit breakers that cut electric power to specific equipment can prevent hazardous situations resulting from the loss of power. Often, fires involving an electrical component are relatively minor and, by a short application of a Class C extinguishant, can be effectively extinguished without disturbing electrical continuity.

The capacity of the fire extinguisher supplied for each major Class C hazard situation should be individually judged according to the following factors:

(1) size of the electrical equipment;
(2) configuration of the electrical equipment – particularly the enclosures of units – that influences how the extinguishing agent is distributed;
(3) effective range of the fire extinguisher stream; and
(4) quantity of Class A and Class B material involved.

For large installations of electrical equipment where power continuity is critical, fixed fire protection is desirable. At locations where such fixed systems are installed, it is practical to also provide Class C portable fire extinguishers units to handle quickly discovered fires; obviously, the number and size of these units can be reduced under such conditions.