All You Ever Wanted to Know About Fire Extinguishers

We now offer a variety of in-house and on-site training classes. Our certified trainers have the ability to conduct live fire or classroom fire extinguisher training classes at your facility. We can also provide individual training classes at our location.

There are basically four different types or classes of fire extinguishers, each of which extinguishes specific types of fire. Newer fire extinguishers use a picture/labeling system to designate which types of fires they are to be used on. Older fire extinguishers are labeled with colored geometrical shapes with letter designations. Both of these types of labels are shown below with the description of the different classes of extinguishers.

Additionally, Class A and Class B fire extinguishers have a numerical rating which is based on tests conducted by Underwriter’s Laboratories that are designed to determine the extinguishing potential for each size and type of extinguisher. Click on any of the topics listed below for additional information that may be helpful to know.

Fire Extinguisher Ratings
Class A Extinguishers will put out fires in ordinary combustibles, such as wood and paper. The numerical rating for this class of fire extinguisher refers to the amount of water the fire extinguisher holds and the amount of fire it will extinguish.

Class B Extinguishers should be used on fires involving flammable liquids, such as grease, gasoline, oil, etc. The numerical rating for this class of fire extinguisher states the approximate number of square feet of a flammable liquid fire that a non-expert person can expect to extinguish.

Class C Extinguishers are suitable for use on electrically energized fires. This class of fire extinguishers does not have a numerical rating. The presence of the letter “C” indicates that the extinguishing agent is non-conductive.

Class D Extinguishers are designed for use on flammable metals and are often specific for the type of metal in question. There is no picture designator for Class D extinguishers. These extinguishers generally have no rating nor are they given a multi-purpose rating for use on other types of fires.

Multi-Class Ratings

Many extinguishers available today can be used on different types of fires and will be labeled with more than one designator, e.g. A-B, B-C, or A-B-C. Make sure that if you have a multi-purpose extinguisher it is properly labeled.

This is the old style of labeling indicating suitability for use on Class A, B, and C fires.

This is the new style of labeling that shows this extinguisher may be used on Ordinary Combustibles, Flammable Liquids, or Electrical Equipment fires. This is the new labeling style with a diagonal red line drawn through the picture to indicate what type of fire this extinguisher is NOT suitable for. In this example, the fire extinguisher could be used on Ordinary Combustibles and Flammable Liquids fires, but not for Electrical Equipment fires.

Types of Fire Extinguishers

Dry Chemical

Dry Chemical extinguishers are usually rated for multiple purpose use. They contain an extinguishing agent and use a compressed, non-flammable gas as a propellant.


Halon extinguishers contain a gas that interrupts the chemical reaction that takes place when fuels burn. These types of extinguishers are often used to protect valuable electrical equipment since them leave no residue to clean up. Halon extinguishers have a limited range, usually 4 to 6 feet. The initial application of Halon should be made at the base of the fire, even after the flames have been extinguished.


These extinguishers contain water and compressed gas and should only be used on Class A (ordinary combustibles) fires.

Carbon Dioxide

Carbon Dioxide (CO2) extinguishers are most effective on Class B and C (liquids and electrical) fires. Since the gas disperses quickly, these extinguishers are only effective from 3 to 8 feet. The carbon dioxide is stored as a compressed liquid in the extinguisher; as it expands, it cools the surrounding air. The cooling will often cause ice to form around the “horn” where the gas is expelled from the extinguisher. Since the fire could re-ignite, continue to apply the agent even after the fire appears to be out.

How to Use a Fire Extinguisher

Even though extinguishers come in a number of shapes and sizes, they all operate in a similar manner.  Here’s an easy acronym for fire extinguisher use:

P  A  S  S  —  Pull, Aim, Squeeze, and Sweep

Pull the pin at the top of the extinguisher that keeps the handle from being accidentally pressed.

Aim the nozzle toward the base of the fire.

Stand approximately 8 feet away from the fire and squeeze the handle to discharge the extinguisher. If you release the handle, the discharge will stop.

Sweep the nozzle back and forth at the base of the fire. After the fire appears to be out, watch it carefully since it may re-ignite!

NFPA 10 Standard for Portable Fire Extinguishers

Chapter 7  Inspection, Maintenance, and Recharging

7.1.2 Personnel.* Persons performing maintenance and recharging of extinguishers shall be certified.

7.2 Inspection.

7.2.1 Inspection Frequency.* Fire extinguishers shall be manually inspected when initially place in service.

7.2.2 Inspection Procedures.  Periodic inspection or electronic monitoring of fire extinguishers shall include a check of at least the following items:

Location in designated place
No obstruction to access or visibility
Pressure gauge reading or indicator in the operable range or position
Fullness determined by weighing or hefting
Condition of tires, wheels, carriage, hose, and nozzle for wheeled extinguishers
Indicator for non-rechargeable extinguishers using push-to-test pressure indicators

7.3.2 Annual External Examination of All Extinguishers Physical Condition.  An annual external visual examination of all fire extinguishers shall be made to detect obvious physical damage, corrosion, or nozzle blockage to verify that the operating instructions are present, legible, and facing forward, and that the HMS information is present and legible, and to determine if a 6-year interval examination or hydrostatic test is due.* Seals or Tamper Indicators. At the time of the maintenance, the tamper seal of a rechargeable fire extinguisher shall be removed by operating the pull pin or locking device.  After the applicable maintenance procedures are completed, a new listed tamper seal shall be indicated.  Corrective Action. When an external examination of any fire extinguisher reveals a deficiency, immediate corrective action shall be taken.

Table Maintenance Involving Internal Examination

7.3.6 Six-Year Examination of Certain Types of Extinguishers. Every 6 years, stored-pressure fire extinguishers that require a 12-year hydrostatic test shall be emptied and subjected to the applicable internal and external examination procedures as detailed in the manufacturer’s service manual and this standard.  Non-rechargeable fire extinguishers shall not be required to have a 6-year internal examination and shall not be hydrostatically tested but shall be removed from service at a maximum interval of 12 years from the date of manufacture.

Chapter 8  Hydrostatic Testing Hydrostatic testing shall be performed by persons who are trained in pressure testing procedures and safeguards complying with 7.1.2 and who have testing equipment, facilities, and an appropriate manufacturer’s service manual(s) available. Personnel performing hydrostatic testing shall be certified by an organization with a certification program acceptable to the authority having jurisdiction.  Hydrostatic testing facilities with a DOT certification [requalification identification number (RIN)] or a TC certification shall be permitted to perform the task of hydrostatic testing without having additional certification as a fire extinguisher technician as outlined in 7.1.2.

8.1.3  A hydrostatic test shall always include both an internal and an external visual examination of the cylinder

Table 8.3.1 Hydrostatic Test Intervals for Extinguishers

Extinguisher Type Test Interval (Years)
Stored-pressure water, water mist, loaded stream, and/or antifreeze 5
Carbon dioxide 5
Wet chemical 5
Dry chemical, stored-pressure, with mild steel shells, brazed brass shells, or aluminum shells 12

NFPA 96 – Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations (Hood Cleaning)

Chapter 4 General Requirements

4.1.5 The responsibility for inspection, testing, maintenance, and cleanliness of the ventilation control and fire protection of the commercial cooking operations, including cooking appliances, shall ultimately be that of the owner of the system, provided that this responsibility has not been transferred in written form to a management company, tenant, or other party.

Chapter 11 Procedures for the Use, Inspection, Testing, and Maintenance of Equipment

11.6 Cleaning of Exhaust Systems.

11.6.1* If, upon inspection, the exhaust system is found to be contaminated with deposits from grease-laden vapors, the contaminated portions of the exhaust system shall be cleaned by a properly trained, qualified, and certified person(s) acceptable to the authority having jurisdiction. Hoods, grease removal devices, fans, ducts, and other appurtenances shall be cleaned to remove combustible contaminants to a minimum of (0.002 in.).

Table 11.4 Schedule of Inspection for Grease Buildup

Type or Volume Inspection

Type or Volume Of Cooking Inspection Frequency
Systems serving solid fuel cooking operations Monthly
*Systems serving high-volume cooking operations Quarterly
Systems serving moderate-volume cooking operations Semi-annually
+Systems serving low-volume cooking operations Annually

*High-volume cooking operations include 24-hour cooking, Charbroiling, and wok cooking.

+Low-volume cooking operations include churches, day camps, Seasonal businesses, and senior centers.

11.6.13 When an exhaust system is inspected or cleaned, a certificate showing the name of the servicing company, the name of the person performing the work, and the date of inspection or cleaning shall be maintained on the premises.


B.6.3.1 Where single-wall ductwork penetrates a non-fire-rated roof assembly, the penetration point shall be of limited combustible or noncombustible construction unless a field applied grease duct enclosure is installed to the top of the roof curb or the clearances.

B.6.4 Openings

B.6.4.1 Openings shall be provided at the sides or at the top of the duct, whichever is more accessible, and at changes of direction.

NFPA 17A – Standard for Wet Chemical Extinguishing Systems

Chapter 7 Inspection, Maintenance, and Recharging

7.1 General. The responsibility for inspection, testing, maintenance, and recharging of the fire protection system shall ultimately be that of the owner(s) of the system, provided that this

Responsibility has not been transferred in written form to a management company, tenant, or other party.

7.2 Owner’s Inspections

7.2.1 On a monthly basis, inspection shall be conducted in accordance with the manufacturer’s design, installation, and maintenance manual or the owner’s manual.

7.2.2 At a minimum, the inspection shall include verification of the following:

  1. the extinguishing system is in proper location.
  2. the manual actuators are unobstructed.
  3. the tamper indicators and seals are intact.
  4. the maintenance tag or certificate is in place.
  5. no obvious physical damage or condition exists that might prevent operation.
  6. the pressure gauge(s), if provided, has been inspected physically or electronically to ensure it is in the operable range.
  7. the nozzle blowoff caps, where provided, are intact and undamaged.
  8. the hazard has not changed, including replacement, modification, and relocation of protected equipment.

7.2.5 At least monthly, the date the inspection is performed and the initials of the person performing the inspection shall be recorded.

7.3 Maintenance

7.3.1* A service technician who performs maintenance on an extinguishing system shall be trained and shall have passed a written or online test that is acceptable to the authority having jurisdiction. The service technician shall possess a certification document confirming the requirements in 7.3.1 and issued by the manufacturer or testing organization that is acceptable to the authority having jurisdiction.

7.3.2* A service technician who has the applicable manufacturer’s design, installation, and maintenance manual and service bulletins shall service the wet chemical fire-extinguishing system at intervals of no more than 6 months as outlined in 7.3.3.

7.3.3* At least semiannually and after any system activation, maintenance shall be conducted in accordance with the manufacturer’s design, installation, and maintenance manual. Maintenance shall include the following:

  1. A check to see that the hazard has not changed.
  2. An examination of all detectors, the expellant gas container(s), the agent container(s), releasing devices, piping hose, assemblies, nozzles, signals, all auxiliary equipment, and the liquid level of all non-pressurized wet chemical containers.
  3. Verification that the agent distribution piping is not obstructed. The owner or owner’s representative shall retain all maintenance reports for a period of 1 year after the next maintenance of that type required by the standard.

7.3.4* Fixed temperature sensing elements of the fusible metal alloy type shall be replaced at least semiannually from the date of installation or more frequently, if necessary, and shall be destroyed when removed.

7.5* Hydrostatic Testing.

7.5.1 The following parts of wet chemical extinguishing systems shall be subjected to a hydrostatic pressure test at intervals not exceeding 12 years

  1. Wet chemical containers
  2. Auxiliary pressure containers
  3. Hose assemblies