Fire and explosion safety

Venting Effective Area : Explosion vent area required to ensure the security of an enclosure.

Risk Analysis : Analysis portraying the current situation to determine the possible accidents, their likelihood and consequences which aims to highlight possible solutions to avoid problematic situations.

ST Classes : Dusts are classified according to their level of explosiveness. ST0 being unreactive dust and ST3 are the most reactive dust. The explosion class dust is determined by the value of the tested Kst. Based on the Kst values, dusts have been categorized into hazard classes:




Electrical Classification : Classification of hazardous areas governed by the Quebec Electrical Code in order to reduce the risk of inflammation or accidents by controlling the electrical equipment within specified areas.

CNESST (formerly CSST) : Organization to which the Quebec government has entrusted the promotion of the rights and obligations of work. It ensures compliance with Quebec workers and employers.

Combustion : chemical reaction of oxidation occurring at high speed, enough to generate heat.

Deflagration : Propagation of the combustion zone at a subsonic speed (less than the speed of sound) through the environment.

Spark Detector : Securing system detecting upstream critical equipment, the passage of sparks in the dust collection system or conduit.

Detonation : Propagation of the combustion zone at a higher speed relative to the speed of sound through the environment.

Hydraulic Diameter : Equivalent diameter for non-circular enclosures used for the calculation of the vent area and for pipe flow calculations.

Minimum Ignition Energy (MIE) : Minimum energy required to initiate the combustion of a cloud of dust, vapor or gas.

Quencher : A passive device for securing enclosure in case of dust, gas or hybrid mixture explosions by releasing the internal pressure while extinguishing the flame generated during the blast. This type of protection is favored when the enclosure must be secured inside a building to protect personnel and equipments.

Explosion Venting : A vent or explosion door is a passive safety mechanism which release the internal pressure of an enclosure in case of an explosion. The vent acts as weakness point and opens at a lower pressure to avoid a more severe explosion due to accumulated pressure inside the enclosure.

Explosion : Bursting or spontaneous rupture of an enclosure due to an increase in internal pressure as a result of a deflagration.

Flash fire : A fire that spreads by means of a flame front rapidly through a diffuse fuel, such as dust, gas, or the vapors of an ignitable liquid, without the production of damaging pressure.

Gas : Gaseous state of matter

Granulometry : Study of the statistical distribution of the size of fine solid particles (dust).

Kst : Parameter defining the properties of powders and combustible dust. Its value is equal to the maximum the rate of pressure rise in a container of one cubic meter. The value of Kst is a caracteristic of explosive dust that can be measured and tested in the laboratory under controlled conditions.

Lower Explosivity Limit (LEL) : Lowest concentration at which a combustible explodes in the air.

Upper Explosivity Limit (UEL) : Highest concentration at which a combustible explodes in the air. A concentration greater than this value will not explode.

Lower Flammability Limit (LFL) : Lowest concentration at which a vapor burns in air.

Upper Flammability Limit (UFL) : Highest concentration at which a vapor burns in air.

Combustible Liquid : Liquid being able to be ignited by a flame, but at temperatures above normal temperatures workplaces (flash point equal or greater than 37.8 ° C). Example: Motor oil.

Flammable Liquid : Liquid that can catch fire and burn under normal temperature workplaces (flash point below 37.8 ° C). Example: Propane.

Fire Ball Distance : Maximum distance at which an explosion released through a vent can spread.

NFPA : NFPA is the acronym for: National Fire Protection Association, an organization created in 1896 to standardize the use of sprinklers. Its role has grown over the years to oversee all areas touching directly or indirectly to fire protection.

  • NFPA 68 : Standard on Explosion Protection by Deflagration Venting
  • NFPA 69 : Standard on Explosion Prevention Systems
  • NFPA 329 : Recommended Practice for Handling Releases of Flammable and Combustible Liquids and Gases
  • NFPA 484 : Standard for Combustible Metals
  • NFPA 652 : Standard on the Fundamentals of Combustible Dust
  • NFPA 654 : Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids
  • NFPA 664 : Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities

Plume : Column of one fluid moving through another in the environment.

Flash Point : Minimum temperature at which a solid or liquid emits vapors sufficient to generate a flammable mixture with air.

Dust : Fine particles that can be easily transmitted in airborne and representing, in some cases, a risk of explosion.

Explosive Dust : A dust is considered: explosive, if there is a rise in temperature and pressure inside a closed container when an air / dust mixture is  in contacted with an ignition source.

Maximal Pressure (Pmax) : Parameter defining the maximum explosion pressure of a cloud of dust under standardized conditions. The value of Pmax is an explosive property for explosive dust that can be measured and tested in the laboratory.

Reduced Pressure (Pred) : Pressure developed during an explosion and detachment of explosion membranes inside an enclosure.

Static Activation Pressure (Pstat) : Design pressure, which is sufficient to initiate the opening of the explosion vent.

Active Explosion Protection : A fire / explosion protection is considered active if the security device is activated by a controller / external detector or an electrical pulse.

Passive Explosion Protection : A fire / explosion protection is considered  passive if the security device is activated by a physical / mechanical principle (pressure variation, gravity, etc.) and is therefore not dependent from an activation or an external sensor.

Explosion Suppression : Active protection system detecting and eliminating chemical explosions. It is possible to stifle an explosion within milliseconds after its outbreak by injecting inhibitor products.

Explosion Isolation : System for preventing the propagation of the flame front of an equipment or process to another. These systems can be passive or active.

Autoignition Temperature, Kinding Point : Temperature at which a solid, liquid or gas can ignite without adding an external source of ignition (spark or flame).

Fire Point : Temperature at which the combustion, once begun, can continue.

Explosion Testing : This test is done in a certified laboratory to determine if a dust is explosive or not. The basic test also determines the main explosive dust caracteristics: maximum pressure (P max), pressure rise rate (Kst).

Pinch valve : Passive or active protection to prevent fire / explosion form the spread of an explosion through a duct system.

Vapor : Gaseous form generated by a body that is liquid or solid.

Backdraft Damper, Blow Back Damper : Fire/explosion protection device that prevents the spread of the blast back into the building or in ventilation equipment via the ductwork.

Abort Damper : Fire/explosion protection device which deflects the air to inside the pipes to the atmosphere in the case of an explosion in the duct system.

Industrial Ventilation

Fresh Air, Clean Air : Outside air from an uncontaminated air intake used to renew the air inside a room or work area.

Spray Area : Dedicated section of a building used for spraying (solvent, paint, stain, …). A spray area is different from a spray chamber by the fact that it is open and not bounded by walls or partitions.

Capture Arm : Mobile capture hood and articulated used for drawing the contaminant emissions (smoke or dust) directly to the source.

Clean Air Diffusion Balloon : Economic device to distribute air evenly at ceilings of a building. These pierced tissue conduits multiple openings that swell when the unit is in operation and contract in the opposite case.

Painting or Spraying Cabin : Dedicated space, equipped with a door or not, used for spraying or painting of pieces. These spaces should be ventilated to:

  • Ensure good surface quality of the parts (minimize overspray)
  • Ensure that worker exposure limits are respected
  • Ensure that lower concentrations do not exceed a quarter of the explosive lower limit (LEL), when applicable.

Local Captation : Aspiration and treatment of contaminants directly at the emission point as opposed to general ventilation.

Clean air per hour : Each occupied building must have a minimum fresh air to allow renewal of the air at regular intervals. The air change rate of an industry is determined in accordance with the regulations on health and safety.

Thermal Comfort : Comfortable feel associated with the thermal conditions of the surrounding environment.

Heat Stress, Thermal Shock : Stress induced due to a heat source in the workplace. Heat or cold sensation affecting the productivity and comfort of workers.

Cyclonic Separation : Dust removal equipment using the rotation of the air by centrifugal force for mechanically separating coarse solid particles from the air effluent.

Clean Air Diffuser : A ventilation distributing clean filtered air or fresh air into the plant through grids or diffusion balloons.

Baghouse, Pulse-Jet, Cartridge or Shaker Dust Collector : Air treatment system for separating dust from the air. The dust contains one or more filter media (filters, bags or cartridges) for removing the air effluent particles present. Sometimes this type of system allows for recirculating the purified air inside the factory.

Scrubber : Air treatment system for separating dust from the air by the use of a liquid, usually water. This type of dust remover contains a mechanism to force the contact between the particles with water droplets and purifying the air. This type of dust collector is mainly used in the case of moist or acidic contaminants.

Dust collection : Action to remove the dust with a processing system

Diffusion Grid : Device to distribute the filtered or clean air inside the plant. The grids can be oriented to reduce or increase the air supply.

Hood : Capture unit for evacuating gases, vapors or dust and lead them to the scrubber or dust collection system. These hoods can take many different forms that have to adapt to the processes and operations that take place.

Exposure limits :

Represents the limit concentrations of a contaminant which defined a worker may be exposed. Most contaminants have one or more exposure limits which are governed by the Regulations on Safety and Health work.

  • Weighted average exposure (TWA)
  • Average exposure limit (AAEV)
  • Short-term exposure limit (STEL)

Definitions of these values can be found on the website of the CNESST.

CFM : Air flow unit. CFM is a cubic foot of air per minute.

Pressure Drop : Frictional dissipation of mechanical energy of the moving fluid in a duct system. This dissipation is mesured in pressure unit (Pascal or inches of water). The pressure drop is influenced by the velocity of the fluid and the geometry of the duckwork.

Plans & Specifications : Official documents certified by an engineer to illustrate, detail and specify the necessary work within the framework of a project. Have signed and sealed documents are a legal requirement for all work governed by the Professional Engineers Act.

Air Recirculation : Principle that the exhaust air of a process is filtered, treated and returned inside of the factory. The recirculating air is an economical way to limit the cost of heating or cooling the compensated air. However, although air may be filtered by a high-efficiency dust removal equipment, certain types of contaminants are not allowed from all forms of recirculation by the regulation.

Heat Exchanger, Heat Recovery : Device that allows the recovery of a fraction of the thermal energy stored in a fluid discharged to the atmosphere to reduce the heating costs of the building or process. There are a wide variety of heat exchangers, however, the air-air exchangers (plate or pipe) and the air heat-exchange fluids are the most common.

Dilution Ventilation Rates : Air change rate associated with a new volume of air (room, factory) and conducted by the General ventilation system. This air exchange rate can be calculated per minute (RAM) or per hour (ACH).

Air Makeup : Clean air supply units used to restore the air discharged from a process. These units can operate with or without air recirculation. This unit must also be able to cool (cool) and / or heat air depending on the desired conditions.

Heating, usually natural gas, can be done over direct heat (contact with burner fresh air) or indirect (transfer by conduction). The direct fire offer superior efficiency, however, some pollutants (unburned gases, carbon monoxide, carbon dioxide) are reintroduced in clean air due to contact with the burner.

Rotary Air Lock : Equipment consists of a sealed frame in which rotates a paddle wheel driven by a motor. Usually used in equipment and silos accumulating material and discharging by gravity, the rotary valve creates a restriction to isolate some equipment against the spread of an explosion.

General Ventilation : Ventilation principle that involves the dilution of contaminants through the fresh air intake in the room or the factory.

Local Ventilation : Uptake of contaminants in a workstation or a workstation.

Mechanical Ventilation : Mechanical devices ensuring the variation of air flow entering and leaving the room or the factory.

Natural Ventilation : Aeration achieved only by the natural convection of air and / or wall openings (windows, apertures, etc.).


Air treatment : Includes control contaminant releases to the atmosphere as well as technical and purification technologies.

Authorization Certificate : Certification required by government authorities to approve the industrial facility compliance. These certificates require technical documentation for all emissions of contaminants and possible environmental risks.

Climate Change : Modifications to the composition of the atmosphere disrupting the climate because of the emission of greenhouse gases.

Stack, Chimney : Vertical duct used to evacuate gases or other contaminants in the atmosphere.

Contaminants : Substance, molecule or compound which effects the quality of the air in the environment.

Volatile Organic Compounds (VOCs) : MDDELCC defines VOCs as follows: The volatile organic compounds (VOCs) are substances formed of at least one carbon atom and a hydrogen atom. They are found in gaseous state in the atmosphere. Several of these compounds involved in photochemical reactions responsible for the formation of ground-level ozone. Others, such as benzene and formaldehyde, are also considered toxic and represent health risk.

Sustainable Development : Conception of the common good taking into consideration the economic, social and environmental aspects.

Atmospheric Dispersion : Evaluation of the impact of air pollution.

Pollutant Sampling : Technique used to evaluate the degree of emission of contaminants inside or outside the plant or facility.

Smoke : Fine dust cloud and / or gas emitted by a source of contaminants.

Oxidiser, Thermal Oxidiser, Regenerative Thermal Oxidiser : This is an air decontamination treatment technique which consists of the burning or contaminants to reduce and emit less harmful pollutants to the atmosphere.

LQE : Acronym for the Law on Environmental Quality. Provincial law stipulating the measures and appropriate boundaries for all issues affecting the environment.

MDDELCC : Acronym for the Ministry of Sustainable Development, Environment and the Fight against Climate Change.

Atmospherical Modelisation : Simulation, according to fluid mechanics, of the dispersion of pollutants in the atmosphere by a scenario specifying specific conditions.

Clean Air Regulation (RAA) : Standard governing the emission of particles and gases applicable in the territory of Quebec.

Law 90 : Regulations on the clean air of the Montreal Metropolitan Community. This regulation takes account of the limits of pollutants discharged into the atmosphere and ambient air as well as wastewater treatment efficiency standards and prohibition of certain processes.

Odour threshold : The perception of an odor differs from each individual. The odor threshold of a contaminant represents the concentration at which 50% of the population is able to detect the odor of this contaminant.