Ignition sources may be:
Flames;
Direct fired space and process heating;
Use of cigarettes/matches etc;
Cutting and welding flames;
Hot surfaces;
Heated process vessels such as dryers and furnaces;
Hot process vessels;
Space heating equipment;
Mechanical machinery;
Electrical equipment and lights
Spontaneous heating;
Friction heating or sparks;
Impact sparks;
Sparks from electrical equipment;
Stray currents from electrical equipment
Electrostatic discharge sparks:
Lightning strikes.
Electromagnetic radiation of different wavelengths
Vehicles, unless specially designed or modified are likely to contain a range of potential ignition sources
Sources of ignition should be effectively controlled in all hazardous areas by a combination of design measures, and systems of work: Using electrical equipment and instrumentation classified for the zone in which it is located. New mechanical equipment will need to be selected in the same way. (See above);
Earthing of all plant/ equipment (see Technical Measures Document on
Earthing)
Elimination of surfaces above auto-ignition temperatures of flammable materials being handled/stored (see above);
Provision of lightning protection
Correct selection of vehicles/internal combustion engines that have to work in the zoned areas (see Technical Measures Document on
Permit to Work Systems);
Correct selection of equipment to avoid high intensity electromagnetic radiation sources, e.g. limitations on the power input to fibre optic systems, avoidance of high intensity lasers or sources of infrared radiation
Prohibition of smoking/use of matches/lighters
Controls over the use of normal vehicles
Controls over activities that create intermittent hazardous areas, e.g. tanker loading/unloading
Control of maintenance activities that may cause sparks/hot surfaces/naked flames through a Permit to Work System
Precautions to control the risk from pyrophoric scale, usually associated with formation of ferrous sulphide inside process equipment
Direct Fired Heaters, Hot Oil Systems and Processes Operating Above Auto-Ignition Temperatures
SOURCE: https://www.hse.gov.uk/comah/sragtech/techmeasareaclas.htm
