TB 011 - Pressurized Dry Chemical Fire Extinguishers

Question 1

What is the chemical that makes up dry chemical?

Answer 1

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

Question 2

What are the three ways to explain the extinguishing action of dry chemical extinguishers?

Answer 2

• 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

Question 3

Dry chemical is most effective on fires involving what?

Answer 3

Flammable liquids, gases and liquefied gases

Question 4

Dry Chemical is fastest and most spectacular extinguishing material for what?

Answer 4

Spilled fuel areas

Question 5

Dry chemical is effective on fires involving what?

Answer 5

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

Question 6

How much more effective is a dry chem as CO2 on hydrocarbon fires, including methane?

Answer 6

Twice as effective

Question 7

Where do you apply the dry chem on fires in grease ducts above stoves?

Answer 7

Into the lower end of the duct

Question 8

A cloud of dry chemical is similar to a what?

Answer 8

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

Question 9

To make a rescue of a occupants in a car using a dry chemical, this procedure shouldn’t be used unless what?

Answer 9

Unless at least two firemen are present-
One for rescue
One for provide protective cover

Question 10

What should you do if a reflash occurs?

Answer 10

Don’t hesitate to engulf them in a cloud of powder

Question 11

Can the dry chemical be used to neutralize acid spills?

Answer 11

Yes

Question 12

How high above a acid spill do you want to hold the nozzle and how should you squeeze it?

Answer 12

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

Question 13

With fires involving leaks of gases, especially those heavier than air, the fire ordinarily should not be extinguished until what?

Answer 13

Control of the gas can be obtained

Question 14

What is the disadvantage of using a dry chem?

Answer 14

Lack of control after the extinguishment

Question 15

The dry chem is ineffective on what type of fires?

Answer 15

Metal fires such as magnesium and sodium

Question 16

Dry chemical, toxic or non toxic?.

Answer 16

Non toxic

Question 17

Why can dry powder be used safely on electrical fires, involving oil cooled electric switches and transformers?

Answer 17

Because of its dielectric characteristics

Question 18

Because of its slight corrosive and abrasive properties, the dry chem should be used with care on which fires?

Answer 18

Fine electrical or electronic gear
Printing presses
IBM equipment
Telephone switchboards

*should be considered secondary

Question 19

The extinguisher has a shell of heavy gauge steel tested to what?

Answer 19

600 psi

Question 20

What kind of hose and squeeze grip valve does it have?

Answer 20

Nylon reinforced hose; positive control squeeze grip valve

Question 21

The nozzle is shaped into what degree fan stream?

Answer 21

60 degree

Question 22

The shell is filled with how many pounds of dry chemical?

Answer 22

20 lbs

Question 23

How many psi is it pressurized to?

Answer 23

165 psi with compressed air

Question 24

What is the dry chem rated at?

Answer 24

20 BC
Capable of extinguishing a 20 square foot deep layer Class B fire
Safe on fire involving energized electrical equip

Question 25

What is the discharge time of a 20 pound dry chem?

Answer 25

Valve fully open is 10 seconds

Question 26

What is the discharge time of the 20 pound CO2 extinguisher?

Answer 26

Will last 60 seconds

Question 27

To obtain the best results, work on with side of the fire?

Answer 27

Windward, floating powder in over the fire

Question 28

What is the effective range the dry chem can reach?

Answer 28

15 to 20 feet

Question 29

To prevent splashing when using on depths of flammable liquids, direct the initial discharge from a distance not closer than what?

Answer 29

6 to 8 feet

Question 30

How should the extinguisher be kept?

Answer 30

Fully charged at all times

Question 31

The pressure gauge should be checked how often?

Answer 31

Checked daily for a full charge

Question 32

The extinguisher will function effectively only so long as the air pressure is between

Answer 32

125 to 175 psi

Question 33

When should you inspect to detect deteriorate worn or damaged parts?

Answer 33

Periodically and after use

Question 34

When should inspect the nozzle for any obstructions or collection of moisture?

Answer 34

Periodically

Question 35

When should you remove the extinguisher from the rack, invert it, and shake to preclude any possibility of the chemical caking?

Answer 35

Once each month