TB 011 - Pressurized Dry Chemical Fire Extinguishers Flashcards
(35 cards)
What is the chemical that makes up dry chemical?
baking soda (sodium bicarbonate, NaHCO 2 ) especially treated to make it resistant to caking and moisture, and capable of being readily dispersedinto a fire-killing cloud
What are the three ways to explain the extinguishing action of dry chemical extinguishers?
- Presence of heat, releases carbon dioxide and water vapor which provides smothering action
- Heat absorbed by solid particles and water vapor which provides cooling
- Chemical chain reaction of combustion is interrupted. Inactivates intermediate products necessary for continued combustion
Dry chemical is most effective on fires involving what?
Flammable liquids, gases and liquefied gases
Dry Chemical is fastest and most spectacular extinguishing material for what?
Spilled fuel areas
Dry chemical is effective on fires involving what?
Deep-layer flammable liquids Natural gas leaks Liquefied flammable gas leaks and spills Dip tanks Ruptured tank cars Broken gas lines Broken valves or flares on liquefied flammable gas cylinders Breaks and leaks in pipes and tubing for flammable gases Anesthetic
How much more effective is a dry chem as CO2 on hydrocarbon fires, including methane?
Twice as effective
Where do you apply the dry chem on fires in grease ducts above stoves?
Into the lower end of the duct
A cloud of dry chemical is similar to a what?
Flame arrestor, flame cannot pass through a cloud of particles
Can be used as a heat screen to quickly move in on the fire and rescue occupants
To make a rescue of a occupants in a car using a dry chemical, this procedure shouldn’t be used unless what?
Unless at least two firemen are present-
One for rescue
One for provide protective cover
What should you do if a reflash occurs?
Don’t hesitate to engulf them in a cloud of powder
Can the dry chemical be used to neutralize acid spills?
Yes
How high above a acid spill do you want to hold the nozzle and how should you squeeze it?
2 to 3 feet above the acid; squeeze just enough to allow the powder to flow gently fro, the nozzle and spread the powder over the surface of the acid
With fires involving leaks of gases, especially those heavier than air, the fire ordinarily should not be extinguished until what?
Control of the gas can be obtained
What is the disadvantage of using a dry chem?
Lack of control after the extinguishment
The dry chem is ineffective on what type of fires?
Metal fires such as magnesium and sodium
Dry chemical, toxic or non toxic?.
Non toxic
Why can dry powder be used safely on electrical fires, involving oil cooled electric switches and transformers?
Because of its dielectric characteristics
Because of its slight corrosive and abrasive properties, the dry chem should be used with care on which fires?
Fine electrical or electronic gear
Printing presses
IBM equipment
Telephone switchboards
*should be considered secondary
The extinguisher has a shell of heavy gauge steel tested to what?
600 psi
What kind of hose and squeeze grip valve does it have?
Nylon reinforced hose; positive control squeeze grip valve
The nozzle is shaped into what degree fan stream?
60 degree
The shell is filled with how many pounds of dry chemical?
20 lbs
How many psi is it pressurized to?
165 psi with compressed air
What is the dry chem rated at?
20 BC
Capable of extinguishing a 20 square foot deep layer Class B fire
Safe on fire involving energized electrical equip
