Determination of fire risk

Four categories, namely: light danger level, medium danger level, heavy danger level and warehouse danger level.

Mild hazard level: buildings for the elderly, children, hotels and office buildings with a building height of 24m or less. Only the buildings in the closed system are set in the walkways.

Medium risk level: high-rise civil buildings: hotels, office buildings, comprehensive buildings, postal buildings, financial and telecommunications buildings, command and dispatch buildings, radio and television buildings (towers), etc.

Severely dangerous level: material preparation workshops of printing plants, alcoholic products, flammable liquid products and other factories. Flammable liquid spraying operation area, solid flammable materials, flammable aerosol products, solvents, paints, asphalt products and other factory materials and the lower part of the production workshop, studio and stage "grape trellis".

Warehouse risk level: food, tobacco and alcohol, incombustible articles packed in wooden boxes and cartons, shelf areas of warehouse-type shopping malls, etc. Wood, paper, leather, grain and its products, cotton, wool, hemp, chemical fiber and its products, household appliances, cables, B-class plastics and rubber and their products, steel-plastic mixed materials products, all kinds of incombustible articles packed in plastic bottles and boxes, and warehouses where all kinds of articles are mixed.

First, the main indicators of fire risk assessment

1. Gas: explosion limit and self-ignition point.

The larger the explosion limit range of combustible gas is, the lower the explosion limit is, the easier it is to form explosive gas mixture with air or other combustion-supporting gases, and the greater the risk of fire and explosion. The lower the spontaneous combustion point of combustible gas, the greater the possibility of fire when it meets heat sources such as high temperature surfaces, and the greater the risk of fire and explosion.

2. Liquid: flash point

The most direct index to evaluate the fire risk of flammable liquids is vapor pressure. The higher the vapor pressure, the stronger the volatility and the lower the flash point. The lower its flash point, the more volatile it is to form an explosive gas mixture, and the easier it is to ignite. For flammable liquids, the self-ignition point is usually used as an index to evaluate the fire risk. The lower the spontaneous combustion point, the easier it is to spontaneously ignite.

3. Solids: melting point and ignition point

Solids with low melting point are easy to evaporate or vaporize, with lower ignition point and faster combustion speed. Many flammable solids with low melting point also have flashover phenomenon.

Powder combustible solid: take the lower limit of explosion concentration as the index.

Combustion of solids in contact with water: the reaction speed with water and the heat released are taken as indicators.

Spontaneous combustion solid: Take the spontaneous combustion point as the index.

Decomposition of combustible solids by heating: decomposition temperature is taken as the evaluation index.

Second, the determination of production fire risk

When there are different fire hazards in any fire zone of the same factory building or fire zone, the fire hazard category produced in the factory building or fire zone should be determined according to the part with greater fire hazard; When the amount of flammable and combustible substances used or produced in the production process is small enough to constitute an explosion or fire hazard, it can be determined according to the actual situation; When one of the following conditions is met, it can be determined according to the part with less fire risk:

1) The production part with high fire risk accounts for less than 5% of the building area of this floor or this fire zone, or the paint part in Class D and E workshops is less than 10%, and the production part with high fire risk is not enough to spread to other parts or effective fire prevention measures have been taken;

2) For the paint workshop of Class D and E workshops, when the closed painting process is adopted, the closed painting space is kept under negative pressure, and the paint workshop is equipped with combustible gas detection and alarm system or automatic explosion suppression system, and the paint workshop accounts for no more than 20% of the building area of the fire protection zone.

Third, the determination of warehouse fire risk

When different fire hazards are stored in the same warehouse or any fire zone of the warehouse, the fire hazard of the warehouse or fire zone should be determined according to the item with the greatest fire hazard.

Note: When several items with different fire risks are stored together, the fire resistance rating, allowable floors and allowable area of the building should be determined according to the requirements of the most dangerous person. Just as a warehouse stores three kinds of goods, A, B and C, a warehouse needs to be designed according to the requirements of a warehouse to store goods.

When the weight of combustible packaging is greater than 1/4 or the volume of combustible packaging is greater than 1/2 of the article itself, the fire risk of D and E storage warehouses shall be determined as Class C.