Fighting Fires with Large Spray Streams - Part 1

Fire Fighting Techniques Using Water Spray

• Water spray is increasingly recognized for its effectiveness in fire fighting, particularly for larger fires.
• Most research has focused on small fires, leaving a gap in understanding the use of spray streams for larger blazes.

Differences Between Spray Streams and Straight Streams

• Major differences include water droplet size, stream shape, and effective reach.
• The efficiency of water spray in extinguishing fires is influenced by surrounding temperatures and the physical conditions of the fire area.

Advantages of Water Spray Streams

• Increased surface area of the cooling medium leads to improved heat absorption from the fire.
• More efficient heat transfer minimizes water damage and enhances extinguishing effectiveness.
• Smaller water droplets convert to steam rapidly, which lowers surrounding oxygen levels; 1 gallon of water can produce about 227 cubic feet of vapor.
• Spray streams provide better shielding for personnel by combating radiant heat and improving working conditions amidst smoke.
• Wider angle stream shapes allow broader area coverage with reduced nozzle movement.
• Higher nozzle pressures enable easier management of hand lines, delivering more gallons per minute.
• Spray streams can be particularly effective for certain flammable liquid and electrical fires, though precautions are essential.

Disadvantages of Water Spray Streams

• Skin friction reduces reach and velocity as water travels toward the fire, resulting in decreased penetration capabilities.
• Air entrainment directed toward the fire could affect the dynamics of fire suppression.
• Finer water sprays may struggle to reach the heated area due to droplet size limitations.
• Smaller droplets are more susceptible to disturbance by wind and drafts, impacting their effectiveness.
• Ventilation and wind can diminish the reach of spray streams.
• Large fires often require substantial water volume and reach, which many spray nozzles cannot deliver simultaneously.
• Working in confined spaces with hot fires may generate steam, making the area less tenable for firefighters.

General Conclusions on Spray Streams

• Spray streams are effective for cooling large flames, provided there is a sufficient volume of water discharge.
• Volume of water is prioritized over pressure for effectively reaching the fire seat, emphasizing the importance of adequate supply.