Seven experimental series with over 100 configurations using two structures reveal the impact of hose stream patterns and nozzle movements on air flow inside structures. (NIST photos)
The National Institute of Standards and Technology (NIST) Fire Research Division released the findings from their experiments on hose streams, nozzle movement and air flow inside a structure. In the paper, “Impact of Hose Streams on Air Flow Inside a Structure”, presented by Joseph M. Willi, Daniel Madrzykowski and Craig G. Weinschenck, the research had two objectives:
· Determine the amount of air movement induced by different hose streams and nozzle movements
· Examine Royer’s nozzle movement theory on the direction of nozzle movement
Royer’s theories on nozzle movement impacting air flow are:
· Clockwise rotation drives most heated gases and smoke away from the nozzle while counterclockwise rotation does the opposite
· Steam formed by the clockwise rotation has a violent rolling action. Counterclockwise rotation produces a lazy action
· Clockwise rotation increases water efficiency and produces a faster knockdown than counterclockwise rotation.
The streams and movements were studied in 154 different configurations in a series of seven tests. The physical property designs used simulated a one-story and two-story residential structure built on the grounds of the Delaware County Emergency Services Training Center in Pennsylvania. Each structure had a simple floor plan and exterior doorways that were opened and closed during the experiments. Neither structure had windows. Throughout each structure the air flow, or gas velocity, was measured at different locations.
In the experimental test series water flowed at 120 GPM from a combination nozzle and 180 GPM from a smoothbore nozzle (1” tip). The experiments that used a “monitor” (nozzle fixed to a non-moving position) the focus of the stream was on changes in point of water application and stream pattern while experiments that used a moveable hoseline focused in the effects of the nozzle movement on the air flow.
The wide fog stream caused the most air movement in the tests. The wide fog reached a velocity of 5.8 MPH and an air flow of 9,000 CFM. The narrow fog, straight stream and solid stream all caused less velocity and flow throughout the structures.
When testing nozzle movement on air flow, in regard to Royer’s theory, it was discovered that the straight stream only caused air movement through the structures when the stream was applied in a moving pattern. It was also determined that there were no significant differences between clockwise and counterclockwise movements on the average air velocity measured through interior doorways.
The results from these experiments show that hose streams can affect air movement inside a structure. The type of stream and method of application will dictate the extent to which ventilation of a structure is impacted and likewise show potential for streams to affect interior air flows inside a burning structure.