Fire flow is also a major part of the risk-hazard analysis. In very general terms, if the fire-flow capability of available resources exceeds the required fire flow, an offensive attack on the fire can usually be made, provided that the proper resources are available to support the operation and circumstances or conditions allow. If the fire flow requirements cannot be met, a defensive mode of operations is required. Fire flow should be determined by the National Fire Academy Formula (taking the length multiplied by the width of the building and dividing it by three will provide the requirement for one floor at 100% involvement; numbers should also be rounded to make the math simple). If multiple floors are involved (including attic spaces) this final number should be multiplied by that factor (number of floors) also. It is also recommended that one firefighter be on scene for every 50 gallons of water flowing to support operations. It is also important to remember that if the fire attack needs to be reinforced more than one time, serious consideration should be given to the strategy that is being undertaken (see Photo 3).
Again, these are not absolutes, but points that need to be considered.
4. Smoke Behavior
The ability to understand the significance of smoke conditions on the fireground is essential. Interpreting smoke conditions can provide a degree of predictability as to what is going to take place on the fireground. With this predictability many dangerous situations can be prevented. It also helps in telling us where the fire is located and how much fire is present. The attributes of smoke provide us the clues to developments such as flashover, backdraft, smoke explosion and rapid fire spread.
Understanding the four basic attributes of smoke is important to all on the fireground. These attributes are volume, velocity, density and color. All must be taken in context to each other as well as in relation to the size of the building or area that is on fire.
- Volume is the first attribute. Volume indicates the amount of fuel that is being off gassed by the combustion process.
- Velocity refers to the speed or push behind the smoke inside the fire area. It is a key indicator to the amount of heat and pressure that have built up within the structure or fire area. Smoke velocity relates to basic principles of physics; heat is inversely proportional to pressure. As heat levels increase, pressure also increases until equilibrium is reached by cooling the environment. Smoke under high velocity or turbulence is indicative of very high temperatures therefore velocity is very useful in monitoring for flashover. An old method to locating the area of fire on the fireground using velocity is to look for the smallest opening exhibiting the fastest moving smoke – usually this opening will be the nearest to the fire.
- Density or the thickness of smoke indicates how much fuel is being burned off in the combustion process. The thicker that smoke is the more fuel that it contains. Rapid fire spread must be a consideration when smoke becomes increasingly thicker. As smoke cools and reaches equilibrium, the solid particulate and aerosols contained in it will bind to surfaces, decreasing the density of smoke as it travels. This process is known as “filtering” – the further away from the fire location, the less dense that the smoke should be.
- Colors of smoke have traditionally been taught to be indicative of specific materials that are burning. For the most part, this is next to impossible to determine on the fireground in the context of how many different chemicals and hydrocarbons that items in our environment are made of. Two colors that have very significant meaning on the fireground though are brown and yellow smoke. Brown smoke tells us that raw or unfinished wood products are burning; an indication that the fire has taken control of structural components. Yellow-tinged smoke is a late indicator of backdraft as it signifies the release of sulfur compounds in substances, which only takes place under extreme heat conditions.
Color can also indicate the duration of time that a fire has been burning, as well as location in regards to distance from the opening it is being seen. As materials burn, they first release moisture, which produces smoke that is lighter in color, as it progresses, and the moisture is burned off, the smoke eventually turns darker (see Photo 4). Color in smoke is also subject to filtering as previously mentioned with density. As smoke travels away from its point of origin, it should become lighter as the solid particulate and aerosols contained in it will bind to surfaces.
5. Rapid Intervention Team (RIT)
Is the provision for a rapid deployment rescue team for the purpose of rescuing lost or trapped firefighters in place? NFPA and OSHA standards state that at least two members of the initial attack crew must be assigned this task (IRIT – Initial Rapid Intervention Team) until resources for a formalized team are on scene. It does not matter what rule, standard or regulation that we are trying to comply with – the bottom line is that firefighter safety must be the main objective. The RIT must be established as soon as possible and be made up of properly trained and equipped firefighters. In addition, they need to have the proper equipment ready based on the type of building that operations are taking place.