THE VOLUNTEERS CORNER
VENTILATION probably leads to more indecisiveness on the fireground than any other aspect of fire fighting. For one thing, most volunteer departments don’t have 1enough fires to become familiar with the many facets of this vital step in extinguishing fires. However, there are many good reasons for making ventilation an important part of any fire department’s operating procedure.
There is the ever-present danger of a backdraft—or carbon monoxide explosion —when opening up a tightly closed building in which a fire has gone through the open-flaine stage into the smoldering stage with attendant high heat. Unless you ventilate properly first, your hose crew may find itself hurled into the street when the entrance of air at the wrong place gives a smoldering fire the oxygen it needs to set off an explosion.
Often that first hose crew fails to make entrance into a building because of the body-punishing heat. The fire attack is stymied until the building is properly ventilated. Many a fireman has found that once ventilation is effected, it feels as though a huge fan is sucking the heat out of the building. Then the hose line can be taken to the seat of the fire.
This rapid dispelling of heat may also be necessary before a rescue can be made. If the structure has many occupants, ventilation can be used to pull heat away from stairways and doors through which people can flee.
Sometimes when there isn’t much heat, there is still so much smoke that you can’t see a nozzle tip in front of your nose. What is burning and where may remain a mystery until some of the smoke is cleared out. This is where volunteers are called upon to use patience. The source of a cellar full of smoke may be only a burning belt on a compressor or an overflow from an oil burner that is going nowhere. An impetuous blast of a hose stream in a situation like this can make you look pretty silly. The resulting water damage may far exceed the possible fire damage.
The cardinal rule for handling any ventilation problem is first to have charged lines in position for instant use. No openings should be made until this has been done—both for the protection of the firemen and for controlling any outburst of flame.
A couple of months ago, we discussed the problem of opening up roofs. This is one method of ventilating a building— what we call vertical ventilation. The other method of venting—by opening up windows or doors or utilizing wall louvers —is known as horizontal ventilation.
Obviously, in roof ventilation, the opening is made at the top of the building. If it can be determined, the hole should be made at the hottest point. If no hot point can be spotted, then the hole should be made at the peak of a pitched roof. If some details of the building’s interior design are known, it is possible to put in a roof hole that will draw the superheated gases away from unburned areas.
In horizontal ventilation, the first openings again should be made at the highest point—the uppermost story. Windows should be opened first on the leeward side and then on the windward side. In this way, the carbon monoxide, which is ever-ready to mix with air explosively, will be vented out of the building before sufficient air is allowed to blow in from the windward side to precipitate a blast. Also, the hot gases won’t pile up on the leeward wall as you try to open windows there.
Double-hung windows should be opened two-thirds down from the top and up one-third from the bottom. This allows heat to escape readily at the top while cool air is entering at the bottom. Don’t forget to remove curtains and draperies which can close off a lot of window area. Screens should be removed. There is a good deal of wire in a screen, and that wire will block off a sizable amount of air.
When to ventilate depends to a great extent on departmental procedure. Where there are many buildings of the same type in the area, general rules may be made that call for immediate action by the officer of the first-due ladder company. In other cases, it is best left up to the officer in charge to order ventilation as he sizes up the fire.
Next month we’ll get into problems of ventilating the types of buildings generally found in communities served by volunteers.