VARIOUS METHODS of horizontal and vertical ventilation were discussed in this column last month. Now let’s get into some structural problems commonly encountered in communities served by volunteers and ventilation applications.

The most common, of course, is a home. Whether it is a ranch type or two stories high, horizontal ventilation will be used most often. You have to have a pretty hot fire before it is worth opening up a roof—but you shouldn’t hesitate when the situation demands it. Delay can rob your efforts of success.

We described how to open windows for horizontal ventilation, starting at the top floor. Don’t overlook the open louvres commonly found in the gable peaks of many modern homes. If the roof has enough of an overhang, a smoke ejector can be attached to the underside of a ladder and placed against the louvre with good results. If there isn’t enough roof overhang, or if a smoke ejector is not available, there is only one practical thing to do—rip out the louvre. You’ll get a freer passage of hot gases to the outside.

One word of caution, however. Make sure that there is enough fire to make ripping out the louvre worthwhile. Ventilation should not lead to unnecessary damage.

Sometimes a few seconds more spent sizing up the situation will lead to discovery of an attic fan which can be turned on and employed with good smoke-clearing effectiveness in minor fires. That same fan, in a larger fire, can draw the flames into the attic as you kiss the roof goodbye.

There are times when the flames are starting to lick their way through the roof as you arrive. Obviously the spot where you see flames coming through is the hottest spot. Hold olf the water until the fire has burned out a good-sized hole and you will have the roof opened up without any trouble.

In ranch homes, fire under the roof tends to run from one end of the house to the other. A hole judiciously placed in the roof can draw the heat away from other parts of the house and forestall the rapid spread of fire. Then you can get hose lines inside the house, where you can box in the fire and extinguish it.

Any fire in an attached garage poses a threat to the house. Here again, a quick hole in the roof can vent off the heat and help prevent the fire from spreading into the house. Always keep in mind that one of the primary reasons for ventilation is to help confine the fire to a given area.

Commercial buildings can be vented by using the same principles employed in houses, but the problems will be affected by the larger size and different types of construction. Often you will find open steel trusses supporting roofs of supermarkets and factories. These trusses heat readily and soon lose their load-carrying capacity.

That means that if you are going to open up the roof, you must do it quickly —before it becomes too dangerous to permit men to work on it. The trend to blank walls in supermarkets often makes vertical ventilation the only choice.

Motels are another type of structure now quite common and motel fires are becoming more frequent. In too many cases, they have no fire walls dividing their extensive areas. Fire reports are filled with stories of blazes that reach into cocklofts and run from one end of the building to the other. Here again, unless rapid roof ventilation is accomplished, the job of containing the fire is tremendous. Get the heat up and out instead of letting it mushroom through a rambling structure.

Once a building is vented, avoid the mistake of putting a hose stream through the opening that is permitting the hot gases to escape. If you do, you’ll cancel out all your work and push the fire hack into the building. Tire object of having a charged line ready when you open up is to prevent the external spread of fire. If you have to knock down flames outside a roof hole or an opened window, shut the line down the moment you have succeeded. Any more water will do more harm than good.

Unusually large buildings like churches, bams and howling alleys provide a formidable challenge to any fire department. The ventilation principles are the same, hut the area and height are a challenge not easily overcome. Unless you accomplish ventilation immediately, the building is generally lost. But if you are lucky enough to get the alarm in time, effective ventilation can be your most valuable step in bringing the fire under control.


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