Flammability limits, effect

Volatile Solids, NFPA 325, Quincy, Mass.). Pressure particularly affects flash point and the uppei flammable limit (UFL) see later section entitled Effect of Temperature, Pressure, and Owgen. Mists of high-flash-point liquids may be flammable the lowei flammable limit (LFL) of fine mists and accompanying vapor is about 48 g/m of air, basis 0°C and 1 atm (0.048 oz/fP). 

Effect of Temperature Pressure and Oxygen LFLs and LOCs at 1 atm decrease about 8 percent of their values at near normal room temperature for each 100°C increase. Upper flammable limits increase approximately 8 percent for the same conditions. 

LPG is considered to be non-toxic witli no chronic effects, but the vapour is slightly anaesthetic. In sufficiently high concentrations, resulting in oxygen deficiency, it will result in physical asphyxiation. The gases are colourless and odourless but an odorant or stenching agent (e.g. methyl mercaptan or dimethyl sulphide) is normally added to facilitate detection by smell down to approximately 0.4% by volume in air, i.e. one-fifth of the lower flammable limit. The odorant is not added for specific applications, e.g. cosmetic aerosol propellant. 

Fire Hazards - Flash Point (deg. F) 175 Flammable Limits in Air (%) Data not available Fire Extinguishing Agents Foam, dry chemical, carbon dioxide Fire Extinguishing Agents Not to be Used Water may be ineffective Special Hazards of Combustion Products Ranunable alcohol and ketone gases are formed in fires Behavior in Fire Bums with a flare effect. Containers may explode Ignition Temperature Data not available Electrical Hazard Data not available Burning Rate Data not available. 

FIRE SIMULATOR predicts the effects of fire growth in a 1-room, 2-vent compartment with sprinkler and detector. It predicts temperature and smoke properties (Oj/CO/COj concentrations and optical densities), heat transfer through room walls and ceilings, sprinkler/heat and smoke detector activation time, heating history of sprinkler/heat detector links, smoke detector response, sprinkler activation, ceiling jet temperature and velocity history (at specified radius from the flre i, sprinkler suppression rate of fire, time to flashover, post-flashover burning rates and duration, doors and windows which open and close, forced ventilation, post-flashover ventilation-limited combustion, lower flammability limit, smoke emissivity, and generation rates of CO/CO, pro iri i post-flashover. 

FIGURE 3-9. Effect of various gases on the flammability limits of methane-inert-gas-air mixtures at 25°C (77°F) and atmospheric pressure (Zabetakis 1965). 

Extreme care must be exercised in designing potentially flammable systems to use reliable flammability limits data and to recognize the effects of pressure/temperature on the data and its implications to the safety of the system in question. Unless otherwise indicated, most published data is at atmospheric pressure and ambient temperature and should be corrected for other conditions. 

The temperature and pressure of a liquid system are important in determining the effects created that result in a fire and explosion hazard. Because this relates to the flash point and flammability limits, see Tables 7-21, 7-22 and Figures 7-48, and 7-49A, and 7-49B [34]. 

The Effect of Elevated Temperature on the Lower Flammable Limit of Combustible Solvents as Encountered in... 

Some organic compounds can be in solution with water and the mixture may still be a flammable mixture. The vapors above these mixtures such as ethanol, methanol, or acetone can form flammable mixtures with air. Bodurtha [39] and Albaugh and Pratt [47] discuss the use of Raoult s law (activity coefficients) in evaluating the effects. Figures 7-52A and B illustrate the vapor-liquid data for ethyl alcohol and the flash point of various concentrations, the shaded area of flammability limits, and the UEL. Note that some of the plots are calculated and bear experimental data verification. 

Flammability. The flammability limits of mixts ofN trifluoride with gaseous fuels and the effect of N as a diluent are given in graphic form in Ref 18. Fuels examined are H, butane, and hexafluoroethane. The authors also report that... 

The effect of natural gravity on flammability limits has been known for a long time. The difference between flammability limits for downward and upward flame propagation was first observed by White [26], for hydrogen/air mixtures. Subsequently, similar effects were also found for other mixtures. For propane flames, the lean flammability limit for both downward and upward propagation was observed to be = 0.53. The rich limits were = 1.64 for downward and = 2.62 for upward propagation. Such wide gap between the flammability limits for rich mixtures is explained in... 

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