portable fire extinguishers

Portable Fire Extinguishers: NFC and NFPA 10

Originally posted on June 7, 2021 at kilolimacode.com

Portable fire extinguisher mounted to column

Mounted Portable Fire Extinguisher

Have you ever seen a similar note on a drawing, “mechanical contractor to provide and install portable fire extinguishers as per NFPA 10”?

While this is true, it’s not entirely accurate.

The National Building Code of Canada (NBC), 2015 Edition requires that portable fire extinguishers be provided and installed in accordance with the National Fire Code of Canada (NFC), 2015 Edition or other applicable legislation (Sentence You then jump over to the NFC and it states, “except as otherwise required by this Code, portable fire extinguishers shall be selected and installed in accordance with NFPA 10, Standard for Portable Fire Extinguishers”. In my experience the “except as otherwise required by this Code” is sometimes overlooked.

In many occupancies the selection and placement of fire extinguishers is straightforward, following the requirements of NFPA 10. However, once we enter the realm of Parts 3, 4 and 5 of the NFC (ie. flammable and combustible liquids, storage occupancies, hazardous processes, etc.), the fire extinguisher requirements are tucked away in each Part. This blog post is intended to identify the additional locations, sizes and types of fire extinguishers that are identified within the various Articles and Sentences scattered throughout the NFC as well as to provide some background information on the basics of NFPA 10.

Selection of Portable Fire Extinguishers

Prior to delving into the requirements in the NFC, it is important to cover some of the basics from NFPA 10. Specifically, Section 5 which is Selection of Portable Fire Extinguishers. This section provides the general requirements for the selection of portable fire extinguishers.

Section 5 identifies several factors to consider when selecting fire extinguishers. Specifically, it identifies the following five factors which are described below. I view these as the general requirements for fire extinguishers.

  1. Classification of Fires

  2. Extinguisher Classification System

  3. Classification of Hazards

  4. Selection for Specific Hazards

  5. Selection for Specific Locations

In addition, the following six factors must also be considered. I view these as the site specific hazards:

  1. Type of fire most likely to occur,

  2. Size of fire most likely to occur,

  3. Hazards in the area where the fire is most likely to occur,

  4. Energized electrical equipment in the vicinity of the fire,

  5. Ambient temperature conditions,

  6. Other factors (See Section H.2)

If you’ve never read through Section H.2, “Health and Safety Conditions That Affect Selection”, you should. Annex material is always interesting to read and provides a wealth of information. The information is also available in the Fire Protection Handbook in the fire extinguisher chapter. Specifically, Table H.2 provides a list of various extinguishers and sizes along with range of the stream and approximate time of discharge. Some handy information to know when people ask questions. Often times I’ll ask someone, “when you squeeze the handle of the fire extinguisher, how long do you think the fire extinguisher will last?” The common response is in minutes, not seconds. They are always surprised that a fire extinguisher will discharge so quickly.

Classification of Fires

NFPA 10 identifies the following 5 classifications of fire:

  1. Class A Fires – Ordinary combustibles, wood, cloth, paper

  2. Class B Fires – Flammable liquids

  3. Class C Fires – Energized electrical equipment

  4. Class D Fires – Combustible metals

  5. Class K Fires – Cooking applications involving combustible cooking media (vegetable and animal oils and fats)

Classifying Occupancy Hazard

In addition to identifying the classifications of fire, it is important to classify the occupancy hazard. There are three classifications of occupancy hazard.

Light Hazard

NFPA 10 defines light hazard as “locations where the quantity and combustibility of Class A combustibles and Class B flammables are low and fire with relatively low rates of heat release are expected. These occupancies consist of fire hazards having normally expected quantities of Class A combustible furnishings, and/or the total quantity of Class B flammables typically expected to be present is less than 1 gal (3.8 L) in any room or area.” Examples from the annex include offices, classrooms, churches, assembly halls, guest room areas of hotels and motels, and so forth. The annex notes that the contents and arrangement of contents will not result in a rapidly spreading fire.

Ordinary Hazard

NFPA 10 defines ordinary hazard as “locations where the quantity and combustibility of Class A combustible materials and Class B flammables are moderate and fires with moderate rates of heat release are expected. These occupancies consist of fire hazards that only occasionally contain Class A combustible materials beyond normal anticipated furnishings, and/or the total quantity of Class B flammables typically expected to be present is from 1 gal to 5 gal (3.8 L to 18.9 L) in a room or area.” Examples from the annex include dining areas, mercantile shops and allied storage, light manufacturing, research operations, auto showrooms, parking garages, workshop or support service areas of light hazard occupancies and warehouses containing Class I or Class II commodities as defined by NFPA 13.

Extra Hazard

NFPA 10 defines extra hazard as “locations where the quantity and combustibility of Class A combustible materials are high or where high amounts of Class B flammables are present and rapidly developing fires with high rates of heat release are expected. These occupancies consist of fire hazards involved with the storage, packaging, handling or manufacture of Class A combustibles, and/or the total quantity of Class B flammables expected to be present is more than 5 gal (18.9 L) in any room or area.” Examples in the annex include woodworking, vehicle repair, aircraft and boat servicing, cooking areas, individual product display showrooms, product convention center displays, and storage and manufacturing processes such as painting, dipping and coating, including flammable liquid handling. Also included is warehousing or in-process storage of other than Class I and Class II commodities.

An important point for designers, NFPA 10 allows up to one half of the required Class A extinguishers to be replaced by uniformly spaced 1½” hose stations.

Commodity Classification & NFPA 10

Commodity classification is noted in both ordinary hazard and extra hazard classifications. If you’ve ever reviewed the commodity classification information in NFPA 13 you know that it’s not an easy topic. This blog post is not about commodity classification, I’ll leave that for the experts. But it is important to note a couple of things. NFPA 13 defines commodity as “the combination of products, packing material, and container that determines commodity classification”. This includes the pallet type. As such, any changes in any of these materials including pallet type, can affect the commodity classification and thus the sprinkler system requirements and fire extinguisher requirements. It is important that the commodity classification and occupancy hazard classification be accurately assessed and documented for future reference. The effects of hazard classification are identified below.

Class A Fire Extinguishers

Fire Extinguisher Size and Placement for Class A Hazards

Therefore, in a light hazard occupancy a single 2-A rated extinguisher can cover up to 6,000 ft2. While a single 2-A extinguisher in an ordinary hazard occupancy can cover a maximum area of 3000 ft2. And a single 4-A extinguisher in an extra hazard occupancy can cover a maximum floor area of 4000 ft2. NFPA provides the following examples of fire extinguisher placement.

Portable Fire Extinguisher Placement - Incorrect Placement

Portable Fire Extinguisher Placement - Incorrect Placement

Portable Fire Extinguisher Placement - Incorrect Placement

Portable Fire Extinguisher Placement - Incorrect Placement

Fire Extinguisher Size and Placement for Class B Hazards

As you can see from Tables and the move from Ordinary Hazard to Extra Hazard has a big effect on extinguisher size and placement. From a minimum 2-A rated fire extinguisher capable of covering 6,000 ft2, to a minimum 4-A rated extinguisher covering 4,000 ft2. And from a 10-B to 40-B with a 30-foot travel distance and from 20-B to 80-B with a 50-foot travel distance.

Class C - Fire Extinguishers

Class C fires involve energized electrical equipment. The fire extinguisher rating for Class C indicates that the extinguishing agent is not electrically conductive and will not pose an electrocution hazard to the user. As such, fire extinguishers for Class C fires should be located considering the hazard classification for a Class A or Class B fire.

Class D – Combustible Metals

Combustible metals are rare in most occupancies we encounter on a day-to-day basis. So, I’ll pass over them in this blog post. Only to note that when combustible metals are present, or expected to be present, specific Class D fire extinguishers for the types of metals present are required.

Class K – Combustible Cooking Media

Class K fire extinguishers are used in commercial cooking applications involving oils and fats. These extinguishers are required to be provided with signage indicating that the canopy suppression system is required to be activated prior to using the extinguisher. These extinguishers should only be used if necessary. The extinguisher is required to be in the kitchen within 30 feet of the hazard.

Extinguisher Classification and Rating System

Each fire extinguisher has a label affixed to it. Annex G provides the following example to break down the rating on the label. “A fire extinguisher is rated and classified 4-A:20-B:C, which imparts the following information:

  1. it should extinguish approximately twice as much Class A fire as a 2-A rated fire extinguisher (2.5 gal (9.46 L)).

  2. it should extinguish approximately 20 times as much Class B fire as a 1-B rated fire extinguisher.

  3. it is suitable for use on energized electrical equipment.”

ULC-S508 – Rating & Testing

ULC-S508, Standard for the Rating and Fire Testing of Fire Extinguishers provides all of the details related to the testing of extinguishers. This is a worthwhile read. It outlines the various fire sizes and methodology for extinguishing a fire and establishing the ratings. This information is always useful to know when questioned about fire extinguishers. For example the numerical portion of Class A rating of extinguishers is developed on the basis of comparative fire tests using various sizes of wood-cribs and wood-panel. In addition, testing is done indoors and outdoors under specific conditions. The numerical portion of Class B Ratings of extinguishers is developed on the basis of fire tests using square steel pans in specific size increments and a flammable liquid test fuel similar to commercial grade heptane. The fire extinguishing classification for Class B is equivalent to 40 percent of the area of fire consistently extinguished by an expert operator. The numeral thus derived is an approximate indication of the relative fire extinguishing potential of the extinguisher. Of note as well there are no numerical components for Class C, Class D or Class K extinguishers.

NFC Fire Extinguisher Location and Sizes

The following table outlines the various hazards, extinguisher rating and code reference from the 2015 Edition of the National Fire Code of Canada.

NFPA 10 also identifies some specific locations, such oxidizer storage , pool chemical storage rooms containing chlorine or bromine as well as commercial kitchens with combustible cooking media and solid fuel cooking appliances. In addition, Section 5.6 of NFPA 10 provides reference to various other standards that contain specific requirements for fire extinguishers. For example, NFPA 33, Standard for Spray Application Using Flammable or Combustible Materials requires a fire extinguisher to be provided in the mixing room in conformance with NFPA 10.

Final Thoughts

Portable fire extinguishers are everywhere. After all the NFC states that portable extinguishers must be installed in all buildings, other than dwelling units. The reality is that most people walk right past them without even noticing them.

Portable fire extinguishers are the first line of defense. They are intended for incipient stage fire fighting. The intent statements for Article of the NFC are predominantly related to limiting the probability that a person would not have access to an extinguisher, thereby allowing the fire to spread beyond the point of origin and potentially harming people. However, the NFC does not require fire extinguisher training for employees. While the rating on a Class B extinguisher may reflect the capabilities of a novice user, it does not consider the potential harm that untrained people may put themselves in by choosing to use a fire extinguisher. Admittedly I have seen several fires extinguished by the public using fire extinguishers. But I have seen many more failed attempts. These failed attempts were a result of one or more of the following: using the wrong extinguisher type, fire was too large, as well as other user errors such as, inability to pull the pin, and misapplication of the extinguishing agent.

There are a lot of misconceptions about fire, partly due to movies. People misunderstand the potential danger involved in fighting a fire. They misunderstand the products of combustion and the hazards that they pose. They misunderstand the extinguishment of fire and the use of fire extinguishers. There is no doubt that portable fire extinguishers can be effective. However, they need to be installed correctly. That is, the right type, size and location. The extinguishers need to be maintained, which is a separate issue. In my opinion people need to be trained in the use of fire extinguishers. Portable extinguishers are part of the overall fire safety strategy outlined in the model codes. Unfortunately, they are often an afterthought and not given due consideration as to the specific hazards that may be in a specific occupancy.

I’m interested in hearing your opinions and experiences on fire extinguishers.

Codes and Standards Referenced

  • National Building Code of Canada, 2015 Edition

  • National Fire Code of Canada, 2015 Edition

  • NFPA 10, Standard for Portable Fire Extinguisher, 2013 Edition