Ignition, open flame

Dust explosions usually occur in pairs. The first explosion involves dust already in suspension. This jars dust from beams, ledges, etc, creating a second cloud to which the explosion propagates, resulting in a secondary explosion. Dust clouds have been ignited by open flames, electric sparks, hot... 

The lower explosive limit (LEL) is the minimum concentration of a vapor in air that will support a flame when ignited. The flash point is the lowest temperature of a liquid that produces sufficient vapor for an open flame to ignite in air. 

Exhaust sparks from engines and burners can be a source of ignition, Any open flame on the facility can also be a source of ignition. 

For a Source of Ignition to occur, there must be an Open Flame or an Electrical Ignition or Mechanical Ignition must be present. Therefore, box 3 is an or gate since only one situation need occur. 

AN 76, N.S.N. 10, K nitrate 10, K perchlorate 2 resin 2% (2) Explosives patented by Distier, Blecher and Lopez (Refs 2 3) (a) AN 88 N.S.N. 12%. It is insensitive to shock or percussion and does not explode when heated to 200° or when ignited in an open flame, but detonates with considerable brisance when strongly initiated. The brisance may be reduced by substituting either K nitrate or Amm perchlorate for part of the AN. (b) AN 85,... 

Silver Picrate (also called Pikratol in Ger). C H2(N02)3 0Ag mw 335.98 N 12.51% fine yel needles mp, 315° with decompn bp, expld ca 335°, or when brought in contact with an open flame was not ignited or detonated by the spit of a fuse when compressed in a detonator cap. Can be prepd by dissolving Ag oxide in a hot satd PA soln (Ref 3)... 

Do not use an aerosol spray when smoking, or near any other source of ignition, e.g. an electric fire, hot-plate, open-flame heater or boiler etc. 

Open flames may ignite hair or loose clothing. 

Open flame may ignite flammable chemicals, loose clothing, or hair alcohol, kerosene, potassium permanganate, hair, clothing Tie back hair. Avoid wearing loose clothing. Avoid open flames when using flammable chemicals. Be aware of locations of fire safety equipment. Notify your teacher immediately. Use fire safety equipment if applicable. 

The flash-point is a measure of the ease of ignition of the liquid. It is the lowest temperature at which the material will ignite from an open flame. The flash-point is a function of the vapour pressure and the flammability limits of the material. It is measured in standard apparatus, following standard procedures (BS 2000). Both open- and closed-cup apparatus is used. Closed-cup flash-points are lower than open cup, and the type of apparatus used should be stated clearly when reporting measurements. Flash-points are given in Sax s handbook, Lewis (2004). The flash-points of many volatile materials are below normal ambient temperature for example, ether —45°C, petrol (gasoline) —43°C (open cup). 

Open flames from process furnaces and incinerators are obvious sources of ignition and must be sited well away from plant containing flammable materials. 

Process areas are divided into two major types of environments XP and non-XP. XP, for explosion proof, means flammable materials (particularly vapors) might be present at certain times. Non-XP means that flammable materials are not present, even under abnormal conditions. For non-XP designated areas open flames, heated elements, and other sources of ignition may be present. 

Ignition arises from a wide variety of sources, including static electricity, hot surfaces, sparks, open flames, and electric circuits. Ignition sources are elusive and difficult to eliminate entirely, although efforts should always be made to reduce them. 

Water curtains can also cool or eliminate available ignition source to a released vapor cloud. In this fashion they can also be a mitigating feature to prevent vapor cloud explosions. Hot surfaces, sparking devices and open flames in the immediate area of a vapor release can all be eliminated as a result of a directed water curtain where these sources exist. 

Molecules such as TATP (49) possess explosive strength similar to TNT. Furthermore, TATP is extremely sensitive to heat and vibrational shock and can be ignited with an open flame or small electrical discharge i.e. does not need a primer unlike conventional explosives. 

Note - AH mentioned before, ether fumes are explosive. Never work with it around an open flame or heating element. Never allow its fumes to build up in the work area. Even the spark fiom a light switch can ignite the fumes. Also use care when venting the fumes as this is one of the chief ways that the authorities uncover illicit drug laboratories. 

Attention also must be given to the explosion and fire hazards presented by combustible organic vapors and combustible gases such as hydrogen and methane. These vapors are readily ignited by static electricity, electrical sparks from most laboratory appliances, open flames, and other highly exothermic reactions. Thus appreciable atmospheric concentrations of combustible vapors should be avoided. 

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