OHS Code Explanation Guide

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

Section 170.1 Spray operations

The fire and explosion hazards of spray application of flammable and combustible materials vary depending on the arrangement and operation of the particular process and on the nature of the material being sprayed. Properly designed, constructed, and ventilated spray areas are able to confine and control combustible residues, dusts, or deposits and to remove vapours and mists from the spray area and discharge them to a safe location, thus reducing the likelihood of fire or explosion. Likewise, accumulations of overspray residues, some of which are not only highly combustible but also subject to spontaneous ignition, can be controlled.

The control of sources of ignition in spray areas and in areas where flammable and combustible liquids or powders are handled, together with constant supervision and maintenance, are essential to safe spray application operations.

(1) Adequate ventilation to remove flammable vapours, mists or powders should be provided at all times, particularly when spray application is conducted in relatively small rooms or enclosures. For enclosed operations, Part 26 of the OHS Code provides design requirements and guidelines for ventilation systems. In addition, the spraying equipment must be interlocked with the ventilation system so that it cannot be used if the ventilation system is not operating.

(2) Spray application should not be conducted in the vicinity of open flames or other sources of ignition. Either the spray operation should be relocated or the source of ignition removed or turned off. Electrical equipment is governed by the area classification requirements described in section 161.1(1)(c).

Other considerations include:

  • containers of coating materials, thinners, or other hazardous materials should be kept tightly closed when not actually being used
  • oily or coating-laden rags or waste should be disposed of promptly and in a safe manner at the end of each day’s operations due to the potential for spontaneous ignition.

If the spray operation takes place indoors but in other than a specifically designed and constructed spray booth, the requirements of Section 5.4 of the Alberta Fire Code (1997) require that:

The operation of any process involving the use of flammable liquids or combustible liquids shall conform to NFPA 33 “Spray Application Using Flammable and Combustible Materials”.

NFPA Standard 33 requires, in general, that,

Each spray area shall be provided with mechanical ventilation hat is capable of confining and removing vapors and mists to a safe location and is capable of confining and controlling combustible residues, dusts and deposits. The concentration of the vapors and mists in the exhaust stream of the ventilation system shall not exceed 25 percent of the lower flammable limit.

In addition, anything that might obstruct ventilation must be at least 6 metres from the spraying location. If it is not reasonably practicable to maintain the 6 metre separation, the spraying area must be ventilated to remove vapours, mists, or powders. Part 26 of the OHS Code provides design and construction requirements.

In this case, all sources of ignition located within an envelope measuring 2 metres above and 6 metres in all other directions from the spraying location must be effectively isolated from the spraying location. One way this can be accomplished is by providing barrier shielding between the ignition source and the spraying operation. Electrical equipment is governed by the area classification requirements as described in section 161.1(1)(c) of the OHS Code.

If the spraying operation takes place outdoors, then anything that might obstruct ventilation must be at least 6 metres from the spraying location. If it is not reasonably practicable to maintain the 6 metre separation, the spraying area must be ventilated to remove vapours, mists or powders. Part 26 of the OHS Code provides design and construction requirements.

Also in this case, all sources of ignition located within an envelope measuring 2 metres above and 6 metres in all other directions from the spraying location, must be effectively isolated from the spraying location. One way this can be accomplished is by providing barrier shielding between the ignition source and the spraying operation. Electrical equipment is governed by the area classification requirements as described in section 161.1(1)(c) of the OHS Code.