Flammable gases definition

Each plant or laboratory should adopt definite rules and procedures for electrical iastahations and work. All iastahations should be ia accordance with the National Electrical Code (NEC) for the type of ha2ard, eg. Class I flammable gas or vapor Class II organic, metallic, or conductive dusts and Class III combustible fibers and the degree of process containment, eg. Division 1 open and Division 2 closed (67). Regardless of the flammabiUty of the materials ia the iastaHed operations, changes ia procedure involving use of such materials often occur, sometimes without concurrent alteration of the electrical iastaHation. 

A combustion process is an exothermic reaction initiated by a source of ignition that produces more energy than it consumes. The speed at which the reaction proceeds through the mixture of reactants depends on the concentration of the flammable gas or vapor. This speed is lower at higher ( rich ) as well as a lower ( lean ) concentrations of the flammable gas than at the stoichiometric mixture. There are lower and upper limits beyond which the reaction cannot propagate through the gas mixture on its own. Some definitions follow ... 

Nonflammable Gas (NFPA 55) A gas that does not meet the definition of a flammable gas. 

If a compressed gas does not meet the criteria of flammability, it is obviously a non-flammable gas. Other definitions involved are ... 

Note Although NH3 does not meet the DOT definition of a Flammable Gas (for labeling purposes), it should be treated as one. 

NFPA 45, 2.2.1.5 4.3.2.1 For the purposes of determining laboratory fire hazard classification and the use of tables 2.2.1(a) and (b) quantities of liquefied flammable gases shall be treated as if they were Class I flammable liquids (see definition) that is, 4L (l.lgal) of liquefied flammable gas is to be considered equivalent to 4L (1.1 gal) of Class I flammable liquid. 

Let us assume that a leak occurs in the wall of the tank and that it can be likened to a circular orifice of known diameter d. There is then formed a jet of flammable gas that causes turbulence, so that the gas mixes with the ambient air. Let us also assume that the gas emerges without igniting and that the jet is definitely monophasic, i.e., there is no change of state caused by part of the gas becoming liquid or solid and this jet is free (i.e. it meets no obstacles). 

Methyl bromide is flammable only in the range of 10 percent to 16 percent by volume in air. Its physical properties do not meet the definition of a flammable gas as defined by DOT and TC. The onset of thermal decomposition occurs at approximately 752°F (400°C). 

Question 1 Please provide an interpretation of potential as it is used in 29 CFR 1910.146(c)(7)(i) as it relates to hazardous atmospheres in the definitions for Non-permit confined space and Permit-required confined space in 1910.146(b). Specifically, does a background or ambient reading of flammable gas, below the specified 10 percent LFL, constitute potential even when there is no source or when all sources have been isolated ... 

If intentional chemistry is performed, chemical reactivity hazards can be expected to exist at your facility. An exception is intentional, essentially complete combustion with air, such as the burning of propane in a gas-fired heater. The burning of ordinary flammable and combustible materials has been excluded from our definition of chemical reactivity hazards and is adequately treated elsewhere. If the answer to Question 5 is YES, then the rest of this section on intentional chemistry need not be considered further, and you should proceed to Question 2 at the beginning of this chapter. 

Ethylene (Ethene or Elayl), H2C CH2 mw 28.05 colorless, flammable, dangerous to handle gas with characteristic sweet odor and taste sp gr 0.975 (air = 1.0), mp —169.4°, bp —103.8°, flash p —136°C explosive limits in air, % by vol, lower 3.0 upper 34.0 si sol in w, more in ale sol in eth. Ethylene is a major component of petroleum refinery gas from cracking units, and is sometimes recovered therefrom by distillation or other means. Some pure ethylene is produced by passing hot ethanol vapors over a catalyst, such as activated alumina (Ref 4). Its laboratory prepn consists of heating ethanol in definite proportions with sulfuric acid of certain concns. By using a 90% acid and 90% ale, ethylene can be produced in a regular stream at a yield of 84 to 85% of theory (Ref 2). 

Heptane is a colorless, flammable liquid that is lighter than, but insoluble in, water. It has a definite petroleum odor that is easily detected at air concentrations of 200 ppm or greater (in air, 1 ppm = 4.10 mgm ). Naturally occurring heptane is isolated from natural gas, crude oil, or pine extracts. 

Flammable liquids or gases and meet the definition of the OSHA Hazard Communication standard [A-7] as a liquid having a flash point <100°F or a gas having a lower flammable limit of 13% by volume or having a flammable range that is wider than 12% by volume. The OSHA Threshold Quantity for flammable liquids and gases is 10,000 pounds. 

The second edition consists of an introduction, four sections, and two appendices. (The appendices present examples and are not part of the consensus document.) Section 1 identifies the scope of the standard and section 2 lists definitions for particular terms. Thus, paraphrasing, adequate ventilation refers to a condition in which air contaminant concentrations are below levels that cause injury or illness, or, that the vapors of flammable liquids are well below the lower flammable limit. A toxic chemical has an oral LD50 for edbino rats greater than 50 mg/kg but not greater than 500 mg/kg, or a 24 hr. skin contact LD50 for albino rabbits more than 200 mg/kg but not more than 1000 mg/kg, or an inhalation LC50 for albino rats more than 200 ppm but not more than 2000 ppm of gas or vapor or more than 2 mg/f but not more than 20 mg/f of dust or mist, provided that such exposures are reasonably likely to be encountered by humans in their use of the chemical. 

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