Designing Fire Suppression Systems

History and Overview

Designing Fire Suppression Systems

Stat-X photo courtesy of Fireaway Inc.

There have been numerous attempts at creating fire suppression systems over the centuries. Even Leonardo DaVinci made an attempt at one that failed.[1] In addition to problematic designs, most of the earliest efforts required someone to activate or operate the system. This created issues because most people were far more interested in escaping the fire than trying to use a fire suppression system.

In terms of “automatic,” i.e., not requiring human intervention to work, two different types of fire suppression systems came on the scene in the 1870s.

  1. The carbon tetrachloride (CTC) glass bulb
    This was mounted in a bracket over a fire risk so that heat from a fire melted a seal dispersing CTC onto the fire. It could also be thrown like a hand grenade onto the fire. The use of CTC was discontinued after it was discovered to be particularly harmful to humans.
  2. Automatic sprinklers
    This system underwent numerous improvements throughout the rest of the 1800s. In 1953, research by Factory Mutual led to an improved spray pattern which is still in use today.

Since the advent of the sprinkler system, fire suppression systems have enjoyed a large degree of improvements and variety. No longer is water the only suppression technology available. There are a multitude of extinguishing agents to select from.

There is also an array of system applications available. Users can choose from focused application systems such as protecting a single electrical panel all the way up to large-area coverage and all points in between. Almost every fire risk has an applicable and target-specific fire suppression system that can be installed.

Today’s fire suppression systems include, but are by no means limited to, installations of one or more of the following:

For fire suppression systems to be most effective, they should be automatic. In most instances this requires that the fire suppression system be connected to a fire detection system. Upon activation of the fire detection system, a signal is sent to the fire suppression system to either activate it or ready it for action.

In some fire suppression systems—such as sprinkler systems and certain condensed aerosol units—the fire suppression system itself functions as both a fire detection system and a fire suppression system. In this situation, the heat from a fire causes the extinguishing agent to be released.

What codes and standards apply to fire suppression systems?

Fire suppression systems can range from remarkably simple (a self-contained condensed aerosol unit) to quite complicated (installations utilizing multiple and different types of fire suppression systems). As one can imagine, there are numerous codes and standards that impact fire suppression system installation(s)[2] . A certified fire protection engineer is usually required in larger, more hazardous facilities, e.g., petrochemical facilities, hospitals, and electrical generation plants; the engineer can recommend, specify, and/or design the fire protection system(s) appropriate for every area of the facility.

For smaller installations, a reputable and certified installer will still be required to adhere to NFPA®[3] codes and OSHA[4] standards, as well as other applicable local fire codes[5]. Further, in many instances (especially involving high-risk facilities or equipment), the insurance company providing fire loss coverage may have fire suppression system conditions. Failure to meet the conditions specified in the policy can result in a claim being denied in the event of a fire-related loss.

NFPA

The scope of this article does not allow for a comprehensive review of all applicable NFPA standards on fire suppression systems (nor would you want to read it). For reference purposes, however, some of the more common and applicable standards include:

Again, this is only a fraction of all NFPA standards that apply to fire suppression systems. Always consult a professional to ensure full compliance with all applicable codes and standards.

OSHA

In addition to NFPA, OSHA also has standards for fire suppression systems which require strict adherence. These include:

As with the NFPA standards, there are additional OSHA standards on fire suppression systems not addressed in this article. Again, it is always advisable to consult a professional or the local OSHA office for guidance on compliance.

Compliance

Meeting the requirements of these codes and standards is not optional. Additionally, the codes and standards are a great resource in fire suppression system design.

What are the different categories and types of fire suppression systems?

Before delving into specific types of fire suppression systems, it is important to describe a few of the categories of fire suppression systems.

Automatic vs. Manual Systems

As mentioned previously, there are undeniable advantages of automatic systems, but there are situations where a manual system makes sense. In some instances, systems may offer both options. Manual system examples include:

Local vs. Total Flooding Systems

This distinction refers to the coverage area of the fire suppression system.

Local systems, also known as pre-engineered systems, apply an extinguishing agent (usually non-water-based) to a particular piece of equipment or specific area. Examples where local systems are used include:

A total flooding system does just what its name implies—it floods the room with agent, floor-to-ceiling and wall-to-wall. Again, the agent is usually not water-based. Typically, it is a gaseous or condensed aerosol agent. Examples where total flooding systems can be used include:

Now we will describe some specific types of fire suppression systems. This is far from an exhaustive list but represents some of the more commonly used systems in place today.

Sprinkler Systems

Photo courtesy of NFPA

Sprinkler systems are probably the most common type of fire suppression system. This is largely because they are so effective—96%:

Unlike their portrayal on TV and at the movies, when sprinkler systems activate, only the sprinkler heads that have been affected by fire discharge water. Most fires are controlled by only 5-6 sprinkler heads being activated. The primary disadvantage of sprinkler systems is water-related damage to goods and the structure.

Sprinkler systems are available in multiple configurations depending on the risk and the installation environment, i.e., freezing vs. non-freezing potential. For more information on the types of sprinkler systems, click here.

Condensed Aerosol Systems

Stat-X photo courtesy of Fireaway Inc.

After the Montreal Protocol in 1987 ended the production of Halon® because of its ozone-depleting properties, it was paramount that a replacement be developed which could protect enclosed special hazards, was environmentally friendly, and did not damage sensitive equipment. Condensed aerosol systems arrived on the fire suppression scene in the early 2000s.

Condensed aerosol systems are available for:

They are far more compact than other gaseous systems and require little to no maintenance while providing exceptionally swift fire suppression. For more information on condensed aerosol systems, click here.

Gaseous Systems

Gaseous Systems

Photo courtesy of William Viker

Gaseous systems, also called “clean agent” systems, are designed for locations where sensitive equipment or materials are involved—such as telecommunication centers, libraries, or museums. Gaseous systems are referred to as “clean” because they do not leave a residue. The clean reference also infers that they do not possess the ozone-depleting characteristics of halogenated hydrocarbons such as Halon®.

There are a variety of gaseous systems available. The primary mode of extinguishment is via rapid heat reduction upon activation of the total flooding system. The systems are usually automatic but can be manually activated as well.

Typical agents used in gaseous systems include:

It is well worth noting that HFCs[6] are subject to a new EPA[7] regulation from the American Innovation and Manufacturing (AIM) Act of 2021. “The AIM Act directs [the] EPA to address the environmental impact of hydrofluorocarbons (HFCs) by: phasing down production and consumption, maximizing reclamation and minimizing releases from equipment, and facilitating the transition to next-generation technologies through sector-based restrictions[8].”

The AIM Act will almost certainly have an impact on availability and price of HFC fire suppression products starting in 2022.

Foam Systems

Most foam systems are employed to suppress fires involving flammable/combustible liquids. With a foam system, foam concentrate is added to water (typically at ratios of 1% to 3% concentrate-to-water), aerated, and applied to the burning fuel. Foam fights fire by cooling the fuel surface, excluding oxygen, suppressing flammable vapors, and separating flames from the burning fuel. Foam systems can be manual or automatic.

Low-expansion foam systems expand foam from 2X to 20X its initial volume, while medium expansion foam expands 20x to 200x its initial volume. Foam systems can be manual or automatic and are typically installed on:

High expansion foam is a special type of foam that is super-aerated by a fan-like device and can expand up to 1000X its initial volume. It is used in large, enclosed areas such as:

CO2 Systems

Photo courtesy of ANSI

CO2 extinguishes fire by excluding oxygen to a point where flaming combustion does not occur. It is used in confined/enclosed spaces. CO2 systems can be manual or automatic and local or total flooding. The system usually consists of large banks of CO2 cylinders manifolded together and piped to the area of application.

The benefits of CO2 are it leaves no residue; it does not damage equipment; it is inexpensive; and it is electrically non-conductive. The disadvantage is that it cannot be used in areas where personnel are present because it can lower the oxygen content of the space to non-survivable levels.
CO2 systems are commonly found in:

While CO2 systems are effective and cost-efficient, the risks in its application must be weighed. To find out more about CO2 systems, click here.

Dry Chemical Systems

Dry chemical systems utilize: a powdered dry chemical in a tank, a cylinder of expellant (usually nitrogen), and piping to nozzles. The dry chemical is usually either sodium bicarbonate, mono-ammonium phosphate, or potassium bicarbonate (Purple K).

Dry chemical systems can either be manual or automatic and are available in local or total-flooding configurations. Dry chemical works very quickly to interrupt the chemical chain reaction of a fire and effect extinguishment when activated.

The primary disadvantage of dry chemical systems is the extensive clean-up after activation. Quite simply, the powder goes everywhere and gets into everything. It can also be corrosive to electronics.

Dry chemical systems can be designed for Class A, B, and C fires. However, the primary application is for Class B fires—flammable liquids. The more common locations for dry chemical systems include:

For more information on dry chemical systems, click here.

Wet Chemical Systems

Photo courtesy of Lafayette.in.gov

Wet chemical systems utilize: a wet chemical in a tank, a cylinder of expellant (usually nitrogen), and piping to nozzles. The systems can be manual or automatic and are installed only as local systems. The wet chemical consists of potassium carbonate or potassium acetate, or a mixture of both, in a water solution.

Used exclusively in cooking applications involving vegetable- or animal-based grease and oils (e.g., deep fryers), the wet chemical mixes with the grease upon discharge to form a foam-like layer over the surface to extinguish the fire. This foam layer essentially serves the same purpose as previously described in the Foam System section.

Wet chemical systems can be installed in restaurants and commercial food preparation facilities in the following locations:

* * *

Fire suppression systems are critical components to protect life and property. They should be included in any new construction, major renovation, or retrofitted in situations where they do not currently exist. The suppression system options available today all but guarantee that there is a fire suppression solution for every risk. To ensure the most appropriate system is selected, it is vital to do your research and due diligence, including consulting applicable codes and standards and utilizing high-quality equipment installed by reputable professionals.

To access the companion article Designing a Fire Detection System, click here.

SOURCES

[1] Gelb, Michael J., How to Think Like Leonardo da Vinci: Seven Steps to Genius Every Day, Dell Publishing, 2000
[2] Codes dictate minimum requirements that can be converted to law by the AHJ (Authority Having Jurisdiction), whereas standards dictate how a system should be designed, built, and tested.
[3] National Fire Protection Association
[4] Occupational Health and Safety Administration
[5] These local fire codes, along with their enforcement, are known as “Authority Having Jurisdiction” or “AHJ.”
[6] Hydrofluorocarbons
[7] Environmental Protection Agency
[8] Source: https://www.epa.gov/climate-hfcs-reduction

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