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Studies on the application of gas cooling as used by firefighters

Bonnier, Jan LU (2017) In LUTVDG/TVBB VBRM05 20171
Division of Fire Safety Engineering
Abstract
Gas cooling is a technique used by firefighters to create a safer work environment inside a compartment fire. By spraying water into the smoke layer, the smoke layer temperature will decrease significantly. Next to the lower temperature, the flammability of the smoke layer will also decrease. Due to the cooling of the fire gases, the smoke layer may contract.

This work focused on different parameters that may affect the efficiency of gas cooling and was based on experiments. A series of tests were conducted inside an adjusted half-scale ISO9705 room. A rotatable nozzle was used to analyse different application methods, spraying times, spray angles and droplet size. Temperatures inside the room, velocities in the door opening and... (More)
Gas cooling is a technique used by firefighters to create a safer work environment inside a compartment fire. By spraying water into the smoke layer, the smoke layer temperature will decrease significantly. Next to the lower temperature, the flammability of the smoke layer will also decrease. Due to the cooling of the fire gases, the smoke layer may contract.

This work focused on different parameters that may affect the efficiency of gas cooling and was based on experiments. A series of tests were conducted inside an adjusted half-scale ISO9705 room. A rotatable nozzle was used to analyse different application methods, spraying times, spray angles and droplet size. Temperatures inside the room, velocities in the door opening and contraction of the smoke layer were measured.

Out of the experimental results, the conclusion was made that there were no large differences between using the sweep or the pulsing method. There is no such thing as the one method that is the best way to apply the water spray to cool the overhead fire gases. When the fire gases must be cooled on a larger distance, pulsing will result in better cooling of the fire gases. The sweep is less influenced by the droplet size. So when the desired work pressure is not possible on the firefighter’s nozzle, and the ideal droplet sizes are not created, the cooling efficiency of the sweep method will be less influenced.

The time between every spray must be as small as possible. It is better to open the nozzle once until enough water is applied into the smoke layer than open the nozzle multiple times for the same amount of water. (Less)
Popular Abstract
Firefighters often have to perform an interior attack in pre-flashover conditions. Gas cooling is a control technique to create a safer work environment inside a compartment fire. By spraying water into the smoke layer, the smoke layer temperature will decrease significantly. Next to the lower temperature, the flammability of the smoke layer will also decrease. Due to the cooling of the fire gases, the smoke layer may contract. Gas cooling is performed in many countries around the world. Different methods are used to spray the water into the smoke layer. Two main methods are applied using a fog nozzle. In the Anglo-Saxon world pulsing is used by firefighters to put water into the smoke layer. Also in South-America, Hong Kong, West- and... (More)
Firefighters often have to perform an interior attack in pre-flashover conditions. Gas cooling is a control technique to create a safer work environment inside a compartment fire. By spraying water into the smoke layer, the smoke layer temperature will decrease significantly. Next to the lower temperature, the flammability of the smoke layer will also decrease. Due to the cooling of the fire gases, the smoke layer may contract. Gas cooling is performed in many countries around the world. Different methods are used to spray the water into the smoke layer. Two main methods are applied using a fog nozzle. In the Anglo-Saxon world pulsing is used by firefighters to put water into the smoke layer. Also in South-America, Hong Kong, West- and Central Europe etc. gas cooling is done using pulses. In the Scandinavian countries, gas cooling is done by sweeping the nozzle spray into the smoke layer.

This work focused on different parameters that may affect the efficiency of gas cooling and was based on experiments. A series of tests were conducted inside a scaled test room in a lab environment. A rotatable nozzle was used to analyse different application methods, spraying times, spray angles and droplet size. Temperatures inside the room, velocities in the door opening and contraction of the smoke layer were measured.

Overall there can be concluded that there is no such thing as the one method that is the best way to apply the water spray to cool the overhead fire gases. However, some minor differences between the pulsing and sweep method are noticeable. When a narrow spray cone is used to cool fire gases on a further reach, pulsing will have a better gas cooling efficiency. If the desired work pressure is not possible on the firefighter’s nozzle, and larger droplets are created, then the cooling efficiency of the sweep method will be less influenced. The time between every spray should be kept as small as possible. It is better to open the nozzle once until enough water is applied into the smoke layer than open the nozzle multiple times for the same amount of total used water. (Less)
Please use this url to cite or link to this publication:
author
Bonnier, Jan LU
supervisor
organization
course
VBRM05 20171
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Gas cooling, Firefighting, Fire Service, 3D-technique
publication/series
LUTVDG/TVBB
report number
5547
other publication id
LUTVDG/TVBB-5547-SE
language
English
id
8915076
date added to LUP
2017-07-05 08:50:07
date last changed
2017-07-05 08:50:07
@misc{8915076,
  abstract     = {Gas cooling is a technique used by firefighters to create a safer work environment inside a compartment fire. By spraying water into the smoke layer, the smoke layer temperature will decrease significantly. Next to the lower temperature, the flammability of the smoke layer will also decrease. Due to the cooling of the fire gases, the smoke layer may contract.

This work focused on different parameters that may affect the efficiency of gas cooling and was based on experiments. A series of tests were conducted inside an adjusted half-scale ISO9705 room. A rotatable nozzle was used to analyse different application methods, spraying times, spray angles and droplet size. Temperatures inside the room, velocities in the door opening and contraction of the smoke layer were measured.

Out of the experimental results, the conclusion was made that there were no large differences between using the sweep or the pulsing method. There is no such thing as the one method that is the best way to apply the water spray to cool the overhead fire gases. When the fire gases must be cooled on a larger distance, pulsing will result in better cooling of the fire gases. The sweep is less influenced by the droplet size. So when the desired work pressure is not possible on the firefighter’s nozzle, and the ideal droplet sizes are not created, the cooling efficiency of the sweep method will be less influenced.

The time between every spray must be as small as possible. It is better to open the nozzle once until enough water is applied into the smoke layer than open the nozzle multiple times for the same amount of water.},
  author       = {Bonnier, Jan},
  keyword      = {Gas cooling,Firefighting,Fire Service,3D-technique},
  language     = {eng},
  note         = {Student Paper},
  series       = {LUTVDG/TVBB},
  title        = {Studies on the application of gas cooling as used by firefighters},
  year         = {2017},
}