T he thicker the smoke, the more spectacular the flashover or fire spread. The greater the smoke density the more likely a hostile fire event, such as flashover or rapid fire spread. Thick or optically dense smoke contains a high concentration of particulates and is difficult to see through. Optical density refers to how difficult it is to see through the smoke. Smoke Density refers to the thickness of the emission and how much fuel is laden in the smoke. In these cases, unless the structure is ventilated and cooled a backdraft, explosive burning of heated gases, will occur due to the improper ventilation. If the velocity of smoke leaving an opening is agitated or turbulent, then rapid-fire progress is likely to occur. The velocity is an indicator of pressure that has built up within the compartment. Smoke Velocity is the speed of the smoke leaving the structure. There can be large volumes of smoke with very little fire. The measure of volume is important but unfortunately, it elucidates nothing much other than location. Smoke Volume can provide a useful indication of the location and indicates the amount of fuels off-gassing within an area. Smoke is made up of particulates, aerosols, and gases, and has four attributes: The art of reading smoke must first start with what comprises the emission. “Watching how fast it is changing can tell if we have seconds or minutes before something happens.” Types of Smoke Signals “Reading smoke can tell us what is happening now and, more importantly, what is going to happen in the future,” said author the author of The Art of Reading Smoke, David W. In the case of a structure fire, it helps us predict hostile fire events like smoke explosions, backdrafts, and flashovers. Smoke can help first responders determine the fire’s location, growth, toxicity, the direction of travel. The ability to read the smoke at any position within the company can help those responding to the incident make better tactical decisions. The Meaning of one puff of smoke meant ATTENTION.One of the most important skills all firemen should possess is the ability to read smoke signals.The simple code used for commonly understood smoke signals was: if there were no enemies who could use the messages to their advantage then a simple code could be generally used. In general, there was not one set meaning as enemy tribes would also be able to read the messages that were being sent. Smoke signals were sent by day and fires conveyed signals at night. Then a number of smaller fires, in a line side by side, might indicate the number of scalps and horses taken. An example of this a single fire was built first with one smoke signal that indicated success in battle. More than one fire and set of signals could also be used. In order to send smoke signals over greater distances, some tribes would set up a chain of fires to relay messages from one location to the next. Pre-arranged signals might also be used to convey the death of a chief or an important birth News: Smoke Signals that signified a battle had been won or lost and even the number of scalps that had been taken or the number of horses that had been won in battle.Help Needed: Smoke Signals that signified that reinforcements were needed in a battle.Warnings and Alarms: Smoke Signals that signified a warning such as sickness or the approach of an enemy or a stranger and even the number of guns that they carried.The types of messages sent by these signals were: The Native Americans used smoke signals to communicate messages over long distances to a number of people. These puffs of smoke rose and according to their number the message to be sent could be varied.It was then lowered, held, and raised again causing a new puff or cloud.When a lot of smoke had been imprisoned beneath it, the blanket was raised so as to let it escape A blanket was so held as to prevent the smoke rising.The addition of other materials such damp leaves or grass encouraged thick smoke and other materials such as oil and animal dung might produce a darker smoke Wood materials produce a tan or brown color. As a material dries out the color of the smoke changes. Virtually all solid materials emit a white "smoke" when first heated which is is mostly moisture.Native Americans discovered that some materials were than others in producing thick, dense, dark smoke to create highly visible smoke signals.Fuel was chosen for the fire that gave a dense, dark smoke.The first requirement was to select an area to set up a smoke signal system that was visible from a great distance.The system used by Native American Indians for sending smoke signals was as follows:
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