Exercise 1. Read and translate the text. The major objectives of a firefighting force are to reach the scene of the fire as quickly as possible

VENTILATION

The major objectives of a firefighting force are to reach the scene of the fire as quickly as possible, rescue trapped victims, locate the fire, and apply suitable extinguishing agents with a minimum of fire, water, smoke, and heat damage. Ventilation during firefighting is definitely an aid to the fulfillment of these objectives. Ventilation, applied to firefighting, is the planned and systematic release and removal of heated air, smoke, and toxic gases from a confined area and the replacement of these products of combustion with a supply of cooler fresh air.

When proper ventilation is accomplished to aid fire control, there are certain advantages that may be obtained from its application. Proper ventilation simplifies and expedites the rescue of victims by removing smoke and gases which endanger occupants who are trapped or unconscious, and by making conditions safer for firefighters.

The removal of smoke, gases, and heat from a building permits firefighters to locate the fire more rapidly and proceed with its extinguishment. Proper ventilation of a building enables firefighters to determine the path of fire spread and to take proper steps for its control. It also reduces the obstacles which hinder firefighters while they perform fire extinguishment, salvage, rescue, and overhaul procedures, by enhancing visibility and removing the discomfort of excessive heat.

When sufficient heat is confined in an area, the temperatures of combustible materials rise to their ignition points. These materials will not ignite, however, unless sufficient oxygen is available to support combustion. In this situation, a very dangerous condition exists because the admittance of an air supply (which provides the necessary oxygen) is all that is needed to change the overheated area into the inferno. This sudden ignition is often referred to as a back draft. In order to avoid or prevent this critical situation from occurring, top ventilation must be provided to release superheated fire gases and smoke.

Firefighters must be aware of this explosion potential and must proceed cautiously in areas where excessive amounts of heat have accumulated. During rescue operations, doors should be opened slightly and carefully so they may be closed quickly, if necessary, to shut off the air supply to extremely hot areas. Situations which create a back draft are confinement and intense buildup of heated gases in an atmosphere being depleted of oxygen. Ventilation is a procedure whereby these gases can be released with a minimum of additional damage to the structure.

Heat, smoke, and fire gases will travel upward to the highest point in an area due to convection until they are trapped by a roof or a ceiling. As they are trapped and begin to accumulate they bank down and spread laterally to involve other areas of the structure. Proper ventilation of a building during a fire reduces the possibility of mushrooming. When an opening is made in the upper portion of a building during ventilation, a chimney effect is created which draws air currents from throughout the building in the direction of the opening.