Investigating Wildfire Extinguishing Methods

Helen Stritzel, Carmen Plowman, Juan Torres, Weiliang Sun, Grant Matthews

Testable Question

• How effective are different methods, including type of suppression and application, of varying flame retardants used to suppress a fire in an alpine environment?

Hypothesis

• If we test different kinds of commonly used fire retardants, then Monoammonium Phosphate will be the most effective fire suppression technique because when dispersed, it cloaks potential fuel sources with a carbon substance when heated, as opposed to saturating the fuel, absorbing heat, or extinguishing the flames on a smaller scale.

Types of Flame Retardants

Monoammonium Phosphate

• MAP is a fire retardant, so it is applied around a wildfire to contain it

• Aerially distributed in powder form to forests and brush lands

• Remains effective until removed manually or by rain

http://www.qrbiz.com/buy_Map-of-the-Ancient-World

Monoammonium Phosphate

1. A cation is released when Monoammonium Phosphate is heated

2. The cation reacts with cellulose from the fuel, producing an ester.

3. The ester thermally degrades, releasing water vapor and carbon that coats the fuel and renders it fireproof

How it Works

http://chemistry.about.com/od/chemistryjokes/ig/Chemistry-Cat/Chemistry-Cat---Cations.htm

Phos-Chek WD 881

• Mechanism

• Mixes with water to become foam

• Reduces surface tension of water and allows fuel to become saturated faster

• Creates a protective foam blanket around fuel

http://en.wikipedia.org/wiki/Phos-Chek

Phos-Chek WD 881

• Benefits• Applied aerially • Is not a significant hazard to human health during its

manufacture or subsequent use.

• Drawbacks• If deposited into a lake or stream, it could result in a fish-

kill.

Carbon Dioxide

• Mechanism• Extinguisher filled with pressurized CO2• Smothers flame, depriving it of oxygen• By far the most common extinguisher

for small-scale fires• Safe and reliable

A CO2 fire extinguisher. Image: http://frakerfire.com/blog/wp-content/uploads/2012/09/co2-mri.jpg

Carbon Dioxide

• Benefits• Portable• No cleanup necessary

• Drawbacks• Purely small-scale method• Expensive to store and maintain pressure, especially as volume

increases

• Impractical for wildfire use

Thermo Gel Fire Suppressant

• Mechanism of fire suppression• Superabsorbent polymer (hydrogel)• Large molecule with many repeating subunits• “Slurry” – liquid blended with solid (similar to concrete)• Soaks hundreds of times its weight in water• Surrounds w/polymer frame, retaining moisture

• Main Use• Thermal fire protection (i.e. structural protection)

Firefighters spread thermo gel to reduce fire spread. Image: http://ktar.com/?nid=6&sid=619505

Thermo Gel Fire Suppressant

• Benefits• Can be applied ahead of time to staunch fire spread• Protects homes and other areas

• Drawbacks• Difficult cleanup

Halon

• “Clean Agent”• Nonconductive• Volatile (evaporates quickly at room temperature)• No residue

• Mechanism• Stops combustion chemically by reacting with the fire’s requisite

fuel and restricting oxygen flow

A Halon fire extinguisher. Image: http://upload.wikimedia.org/wikipedia/co

mmons/d/d9/FireExtinguisherABC.jpg

Halon

• Benefits• Clean agent• Quick and effective

• Drawbacks• CFC (Chlorofluorocarbon)• Contribute to atmospheric ozone depletion• Usage ended in 1994 w/government restrictions

• Relatively small-scale extinguishing technique (may not apply to wildfires)

Effect of CFCs on the atmosphere. Image: http://www.daviddarling.info/images/chlorofluorocarbons.gif

Proposed Investigation

1. The experimenters will set up a controlled mock burn site created from typical alpine fuel..

2. The fire retardants, MAP, Phos-Chek, and Thermo Gel, will be applied from a height simulating aircraft movement, and the fire extinguishers, Halon and Carbon Dioxide, will be applied to the fire using safe techniques.

3. The fire will then be set for each trial and the time taken for the fire to either run out of fuel from being contained or extinguished using the agents mentioned about will be recorded.

Proposed Investigation

• Independent Variable: Type of fire suppressant

• Dependent Variable: The amount of time taken for a set fire to be extinguished

• Controlled Variables: The type of fuel used in each trial, the same amount of fuel used and the same surrounding environment.

Variables

Bibliography

• Basic facts about Halon. (n.d.). Retrieved March 11, 2014, from http://www.h3rcleanagents.com/support_faq_2.htm

• Fire & aviation management. (n.d.). Retrieved March 7, 2014, from http://www.fs.fed.us/fire/retardant/

• Firefighters say gel works, but don't expect rush to stockpile it. (2007, October 12). Retrieved March 10, 2014, from http://ktar.com/?nid=6&sid=619505

• Firefighting chemicals. (n.d.). Retrieved March 7, 2014, from http://www.cfs.sa.gov.au/site/about_us/what_we_do/aerial_firefighting/firefighting_chemicals.jsp

• Makowka, N. (n.d.). Wy carbon dioxide (CO2) in fire suppression systems? Retrieved March 11, 2014, from http://www.nafed.org/whyco2

• Phos-check WD-881 Class A foam. (n.d.). Retrieved March 7, 2014, from http://www.phos-chek.com.au/foam/phos-chek-wd-881

• Phosphate based forest fire retardants. (n.d.). Retrieved March 7, 2014, from http://www.phosphatesfacts.org/pdfs/Phosphate%20Based%20Forest%20Fire%20Retardants.pdf

• Wildland fire chemical products toxicity and environmental concerns general information . (2007, January). Retrieved March 7, 2014, from http://www.fs.fed.us/rm/fire/documents/

envissu.pdf