Selected Highlights of the Labs21 2009 Annual Conference

Mark L. Robin, Ph.D., and Helen R. Lowery, DuPont Fluoroproducts

Laboratory Fire Protection with Clean Agents

Introduction

Clean agent fire suppression systems are employed to protect valuable assets and in instances where the potential for asset damage due to the fire suppression agent itself is a concern, for example, protecting expensive and sensitive assets such as laboratory and electronic equipment where secondary damage from suppression agents such as water, foam, or dry powder can result in more damage to the protected assets than from the fire itself.

The clean fire suppression agents included in NFPA 2001 Standard on Clean Agent Fire Extinguishing Agents are widely employed, and currently protect billions of dollars worth of assets worldwide. This paper discusses the history, use, and application of clean agents for the protection of laboratory equipment and assets.

Halons: The Original Clean Agents

U.S. Army-sponsored research in the late 1940s led to the development of the original “clean agents,” the halon agents, Halon 1301 (Bromotrifluoromethane, CF3Br) and Halon 1211 (Bromochlorodifluoromethane, CF2BrCl).

Halons 1301 and 1211 are characterized by high fire suppression efficiency, low toxicity, low residue formation following extinguishment, low electrical conductivity, and long-term storage stability. Because these agents produce no corrosive or abrasive residues upon extinguishment, they are ideally suited to protect areas such as libraries and museums, where the use of water or solid extinguishing agents could cause secondary damage equal to or exceeding that caused by direct fire damage. Because they are non-conducting, they can be employed to protect electrical and electronic equipment, and because of their low toxicity, they may be employed in areas where the egress of personnel may be undesirable or impossible.

An additional advantage of clean agents is that they leave no residues behind. As a result, there is no cleanup after their use. This allows for business continuity (i.e., no interruption in services required following the discharge of a clean agent system). The financial impact of service disruptions can be significant, especially in telecommunications facilities and in data processing centers. The estimated downtime impact per minute for various business applications is shown in Table 1. The downtime impact for a typical computing infrastructure is estimated at $42,000 per hour. Downtime impacts for companies relying entirely on telecommuni-cations technology, such as online brokerages or e-commerce sites, can reach $1 million per hour or more.


Table 1: Downtime Impact per Minute for Various Business Applications
Source: Alienan 2004

Business Application

Estimated Outage Cost Per Minute

Supply Chain Management

$11,000

Electronic Commerce

$10,000

Customer Service Center

$3,700

ATM

$3,500

Financial Management

$1,500

Messaging

$1,000

Infrastructure

$700

 

Because of their unique combination of properties, halons served as near ideal fire suppression agents and have been widely employed in laboratories and other applications during the past 30 years. However, due to their implication in the destruction of stratospheric ozone, the Montreal Protocol of 1987, identified Halon 1301 and Halon 1211 as two of a number of halogenated agents requiring limited use and production. An amendment to the original Montreal Protocol resulted in the halting of the production of Halon 1301 and Halon 1211 on January 1, 1994.

Halon Replacements

As a result of the provisions of the Montreal Protocol, the ideal halon replacement, in addition to possessing the desirable characteristics of the halons, is required to have a smaller environmental impact on ozone depletion. The ideal halon replacement would, therefore, be characterized by the following properties:

  • Clean (no residues)
  • High fire extinguishment efficiency
  • Low chemical reactivity

    • Long-term storage stability
    • Noncorrosive to metals
    • High material compatibility (metals, plastics)
  • Electrically non-conducting
  • Low toxicity
  • Zero ozone depletion potential (ODP)
  • Reasonable manufacturing cost

In response to the demise of halon agents, intensive research has been conducted over the past 20 years with the goal of developing viable alternatives for halon agents. As of a result of these efforts to replace Halon 1301 and Halon 1211, four classes of new clean agents have been commercialized, including hydrofluorocarbon (HFC) agents (e.g., HFC-227ea), inert gas agents (e.g., argon, nitrogen, and inert gas blends), hydrochlorofluoro-carbon (HCFC) agents (e.g., blends based on HCFC-123), and a perfluoroketone (PFK) agent (F-ethyl isopropyl ketone). Table 2 provides a comparison of the four classes of clean agents.

Table 2: Clean Agents

 

 Agent

Chemical Structure

 Tradename

 Characteristics

 

HFCs

HFC-227ea

HFC-236fa

CF3CHFCF3

CF3CH2CF3

FM-200®

FE-36 TM

Most cost-effective clean agents

Inert Gases

IG-541

N2/Ar/CO2

Inergen TM

Lowest environmental impact

 

HCFCs

 

HCFC Blend A

CF3CHCl2

CF3CHFCl

CF2HCl

NAF-S-III

HCFCs slated for phaseout

Perfluoro- ketone

FK-5-1-12

CF3CF2C(O)CF(CF3)2

Novec TM 1230

Chemically reactive


The HCFC clean agents are scheduled for phaseout due to their contribution to the depletion of stratospheric ozone and are not sustainable agents. The perfluoro-ketone agent is characterized by high chemical reactivity, reacting with water, alcohols amines, and common solvents. As a result, it is inappropriate for protecting facilities where chemicals are present. Consequently, the clean agent market is dominated by HFC and inert gas agents.

Inert gas agent systems are characterized by low environmental impact, but require high pressure piping and large numbers of cylinders that have weight, space, and cost disadvantages. HFC clean agent systems have weight, space, and cost advantages compared to the inert gases, and are characterized by moderate environmental impacts.

Laboratory Fire Protection

Laboratory fire protection consists of both total flooding systems and portable extinguishers. In total flooding applications, the protected enclosure completely filled ("flooded") with a gaseous suppression agent, resulting in flame extinguishment. Due to the three-dimensional nature of gases, hidden or obstructed fires can be extinguished. In portable applications, a liquid stream of the agent is directed onto the fire location, affording flame extinguishment.

Total Flooding Systems

Requirements for the design, installation, and maintenance of clean agent suppression systems are included in NFPA 2001 Standard on Clean Agent Fire Extinguishing Agents. To protect laboratories, clean agent systems must also comply with NFPA 45 Fire Protection for Laboratories Using Chemicals and with NFPA 72 National Fire Alarm Code. Total flooding (automatic) systems must also comply with UL 2166 Halocarbon Clean Agent Extinguishing Systems or UL 2127 Inert Gas Clean Agent Extinguishing Systems. These automatic systems employ rapid detection and rapid agent discharge to extinguish fires while in their incipient stage, limiting the damage to valuable assets. Typical applications of these clean agent systems include protecting chemical and other laboratories, chemical laboratory fume hoods, clean rooms, flammable storage areas, and computer rooms.

HFC and inert gas systems are suitable for use in occupied areas and for the suppression of Class A (cellulosic), Class B (liquid and gas), and Class C (electrical) fires. HFC systems (i.e., FM-200®) are the most widely employed clean agent systems for laboratory protection due to their lower cost and smaller storage space requirements compared to the inert gas systems; the perfluoroketone agent is not appropriate for the protection of areas containing chemicals due to its high chemical reactivity.

Portable Extinguishers

NFPA 45 Fire Protection for Laboratories Using Chemicals requires that all laboratories be equipped with portable extinguishers. Requirements for the design, installation, and maintenance of clean agent portable fire extinguishers are included in NFPA 10 Standard for Portable Fire Extinguishers, and for the protection of laboratories, portable extinguishers must also comply with the requirements of NFPA 45. Portable extinguisher units must also comply with UL 711 Rating and Fire Testing of Extinguishers.

Currently available clean agent portable systems consist of Halotron I (HCFC-123 based) and FE-36 (HFC-236fa) portable units. Both are suitable for use on Class A, B, and C fires, and portable units are available with various UL ratings (e.g., 1A:10BC, 2A:40BC, etc.). Halotron I consists primarily of HCFC-123, which is slated for phaseout due to its non-zero ODP.

Conclusion

Clean agent fire suppression systems are employed to protect valuable assets and in instances where the potential for asset damage due to the fire suppression agent itself is a concern, for example, protecting expensive and sensitive assets such as laboratory and electronic equipment where secondary damage from suppression agents such as water, foam, or dry powder can result in more damage to the protected assets than from the fire itself. Clean agent systems are available for both total flooding and portable applications and offer effective protection against Class A, B, and C fires with no subsequent requirement for cleanup or business interruption.

 

Biographies

Mark L. Robin, Ph.D., is a technical services consultant for DuPont Fluoroproducts and has over 25 years of experience in the area of fluorine chemistry and 20 years of experience in the fire suppression industry. Mr. Robin has been extensively involved in the development, testing, and approval of halon alternatives, including HFC clean extinguishing agents, and has participated on numerous fire suppression related technical committees including NFPA 2001 and ISO 14520. Mr. Robin is also the recipient of the 2005 U.S. EPA Stratospheric Ozone Protection Award, presented for his efforts in the development of halon replacements and international standards regulating their use.

Helen R. Lowery is the fire suppression agents account manager for DuPont Fluoroproducts. Ms. Lowery is active in numerous clean agent related committees and serves on the board of the Fire Suppression Systems Association.