OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 10 Fire and Explosion Hazards

Section 166 Internal combustion engines

Subsections 166(1) through 166(4)

Flammable substances can give off vapours under the right conditions. If flammable vapours enter the intake of an internal combustions engine, the engine may run uncontrollably and fail to shut down when the normal fuel source is removed. A flashback from the engine cylinders could ignite the gas or vapour in the air. Whenever possible, the internal combustion engines driving stationary equipment should be located outside the hazardous location.

Except for a vehicle powered by an internal combustion engine [see subsection 166(4)], an internal combustion engine used in a hazardous location must have a combustion air intake and exhaust discharge that are equipped with a flame arresting device or the air intake and exhaust discharge must be located outside the boundaries of the area classified under section 162.1. Flame arresting devices prevent a flame front from leaving the engine and igniting the atmosphere in the hazardous location.

If an internal combustion engine is present in a hazardous location, the temperature of all its surfaces exposed to the atmosphere in that location must be lower than the temperature at which the flammable substance(s) present in the hazardous location will ignite. This requirement does not apply to a vehicle that is powered by an internal combustion engine as the engine in the vehicle must be considered a source of ignition. Instead, the requirements of section 169 involving hot work apply.

Subsection 166(5)

An internal combustion engine cannot be located in a hazardous location classified as Zone 0 as explosive concentrations of gas or vapour are present for long periods in these areas. Section 18 of the CEC only allows the use of intrinsically safe electrical equipment that has insufficient energy to ignite the gas in the area in Zone 0 hazardous locations.

Subsection 166(6)

While a hazardous location classified under Section 162.1 as Class I, Zone 1 or Class I, Division 1 will have explosive concentrations of gas present for shorter periods than a Zone 0 hazardous location, explosive concentrations of gas or vapour may be present for relatively long periods. An internal combustion engine located in a Zone 1 hazardous location must have a combustible gas detection system and controls in accordance with Rule 18-070 of the CEC. This Rule requires that

(a) if the gas concentration in the air reaches 20% LEL, an alarm must be activated and additional ventilation must be activated, and
(b) if the gas concentration reaches 40% LEL the engine must be shut down.

Subsection 166(7)

Internal combustion engines are not allowed in Class II or Class III, Division 1 hazardous locations due to the high risk of igniting dust or fibres in those areas.

For further information about Zones and Divisions as classified under the CEC, readers are referred to the explanation for section 162.