Demystifying clean agents
Published: 14 September, 2012
Al Thornton, Global Market Manager, DuPont Fire Extinguishants, answers some of the common questions surrounding clean agents. Clean agents have been used since the early 1900s but due to toxicity concerns general acceptance didn’t really occur until the introduction of Halons (mainly Halon 1301 and Halon 1211) in the 1960s. Research into the reasons for depletion of the Earth’s ozone layer in the 1970s and 1980s led to the Montreal Protocol which resulted in the prohibition of Halon in most countries and newer non-ozone depleting alternatives were introduced.
Despite being around for over 20 years there are still many common questions and misconceptions surrounding the current clean agents in use so it’s definitely time to try to debunk some of the most common queries.
What is a clean agent?
A clean agent is formally defined as an electrically non-conducting, volatile, or gaseous fire extinguishant that does not leave a residue upon evaporation. Basically a clean agent will extinguish the fire without damaging the contents of the room and will not leave a mess to clean up. The only damage experienced post-fire will be from the fire itself and with a well-designed system, the damage potential is minimal. Cleanup post-fire is limited to those items directly involved in the fire and business interruption is minimized, or in many cases entirely eliminated. There are two main standards that cover the use of clean agent fire extinguishers, the U.S. NFPA 2001 (2012 edition) and ISO 14520 (and the EN 15004 equivalent). Both of these standards address the use of clean agents as total flooding agents and exclude carbon dioxide, which is covered by different standards.
Can I still use Halon (1301 and 1211)?
There are a few exceptions regarding Halon use for military and aerospace applications, but in general, the installation of new systems using Halons is not allowed. Halon alternatives such as inert gases, for example, IG-55 or chemical agents, DuPont FM-200 are freely available and widely used.
What is a total flooding agent ?
As the name suggests,this is an agent that is used to flood the entire volume of the space containing the hazard. For this reason, the agents must be volatile or gaseous, sothat the agent can reach all parts of the room. This is essential as many hazards may be inside cabinets or covered areas and the agent must beable to easily penetrate into these obstructed or hidden areas to extinguish the fire before it spreads. An agent that contains small particles (aerosols) or fine liquid droplets (water mist) will be less effective in these situations which may delay the extinguishment of the fire and result in more damage being caused. Total floodingagents are generally intended to be used in enclosed spaces.
How does a clean agent work?
The fire tetrahedron is a geometric representation of the four factors necessary for fire:remove any one of these factors and the fire will be extinguished (Figure 1). Different agents work in different ways. Halonsare very effective as they block the chemical reactions which occur in a fire and also remove heat. Inert gases deplete the oxygen to below the level required to sustain the fire whilst chemical clean agents (such as DuPont FM-200) primarily remove heat to extinguish the fire. Although not as effective as Halon, the alternatives are effective at extinguishing fires rapidly without causing damage from the agent itself. Are clean agents safe to use in occupied spaces? If there is a fire in an occupied space, then all personnel should evacuate the area, regardless of the fire protection measures in place.
If a clean agent system is installed and designed in accordance with either the NFPA 2001 or ISO 14520 standards, then it will be safe for use in occupied spaces even if personnel are still in the space at the time of agent discharge. Both standards contain tables showing maximum exposure times for various agent concentrations with a maximum of 5 minutes for all agents. For the chemical clean agents the standards contain tables showing the NOAEL (No Observable Adverse Effect Level) and LOAEL (Lowest Observable Adverse Effect Level) values. These values are determined by testing on dogs under artificial conditions and are considered a highly conservative indicator of the potential in humans. It is estimated that a concentration that is four to ten times greater would be required to produce the same result under natural maximum stress conditions. The design extinguishing concentrations for normal Class A, Class B and Class C fires for all agents are below the concentrations determined to have any adverse effects and therefore the agents are safe for use in occupied spaces.
How can I be sure the system will work?
Reputable system manufacturers are subject to rigorous listing and approval processesrequired by independent certification organisations such as Underwriters Laboratories (UL), Factory Mutual (FM), VdS or LPCB. These organisations examine and test systems and their associated design software in order to verify their effectiveness and reliability. Using a system manufacturer that has successfully completed listing and/or approval by a recognised independent certification organisation is the best way to ensure the system will operate correctly when called upon to operate. Ensuring the equipment has been listed and/or approved can also guarantee the quality of the agent used. In the case of UL listings and FM approvals, the agent manufacturer also needs to gain approval for their agent.
Does use of chemical clean agents cause corrosion?
The pure clean agents themselves will not cause corrosion and in the case of HFCs like DuPont FM-200 they are particularly chemically stable and compatible with a wide range of materials. All halocarbon agents, including the Halons, will produce decomposition products when exposed to flame temperatures. Studies have been performed examining the quantity of decomposition products produced in a variety of fire scenarios.
In Class A and Class C fires typical of those encountered in IT and telecommunications facilities, it has been shown that the amount of decomposition products formed is well below levels harmful to humans or equipment. Halons were widely banned, will these replacement clean agents also be banned? Halons are very powerful ozone depleting chemicals contributing to 30% of the total ozone depletion at its peak use in the 1980s and early 1990s. Production of new halon was eliminated by the Montreal Protocol and the subsequent amendments. Clean agents such as DuPont FM-200 and DuPont FE-25 are HFC-based agents; are non-ozone depleting; and are not covered by the Montreal Protocol.
HFC clean agents are global warming chemicals, will they be banned by the Kyoto Protocol?
The Kyoto Protocol (KP) was introduced in 1997 and came into force in 2005. The protocol is concerned solely with the reduction of emissions of manmade gases that could cause climate change. These gases include carbon dioxide as well as chemicals such as HFCs. The KP does not propose any bans, restrictions or production limits on use of any chemical but requires participating members to commit to emission reductions for specific greenhouse gases (GHGs) that can promote climate change.
Does the EU F-Gas Directive ban the use of HFCs in fire protection?
The EU F-Gas directive came into force in 2007 and details measures member states must take in terms of training, maintenance regimes and consumption reporting of systems using F-gases such as HFCs in various applications, including for fire protection. The directive does not specify restrictions on the use of HFCs in fire protection applications. During 2012, the F-Gas Directive has been reviewed and the final report is expected to be published by the end of the year. The expectation is that the review will not significantly change the use of HFCs for fire protection applications. Clean agent HFCs have a high GWP – does this mean they are significant contributors to global warming? Products are very often compared by using their Global Warming Potential (GWP) values. GWP values are published by organisations such as the United Nations Environmental Programme (UNEP) and are a convenient way of comparing the potential global warming effect of 1 kg of one product compared to carbon dioxide.
The GWP value of a gas by itself however is not a measure of the overall impact of the gas on climate change. It is just one parameter of many required to determine the impact of a gas on climate change. By far the most important factor in determining the impact of any product on climate change is the amount of emissions of the product to the atmosphere. It’s rather like estimating the fuel economy of a car by being told only how much fuel is in the tank. Unless you know how many kilometres the car will travel on that quantity of fuel,you can’t possibly know how good or bad the fuel economy might be. Emissions of HFCs used for fire protection applications have been reported for a number of years and despite strong growth in the number of installed systems the emissions have not increased.
The chart shown in Figure 2 shows the data gathered from 2002 to 2010 for emissions in North America and is typical of other regions. In Appendix A of NFPA 2001-2012 edition tables A.1.6(b) and A.1.6(c) show the total emissions of GHGs and the emissions from fire protection equipmentas estimated by the US EPA. From this data it can be calculated that the overall impact of HFC emissions from fire protection systems on climate change is 0.01% of the total. To put this into context, for every 1ºC of global warming that may occur, HFCs from fire protection systems contribute 0.0001ºC to the 1 ºC rise. As a result of the continued responsible attitude of the fire protection community to maintain emissions at minimal levels, the benefits of using HFCs in fire protection systems far outweigh any potential threat for climate change.
Will using HFC clean agents for fire protection affect the LEED credits available for a project?
The US Green Building Council (USGBC), a non-profit coalition of building industry leaders, developed the LEED system to establish a common standard of measurement for environmentally sustainable building practices. HFC based clean agents help to contribute to LEED credits in the Energy & Atmosphere category. The Ozone Protection section requires that projects 'do not operate fire suppression systems that contain chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) or Halons' in order to merit certification. Specifying clean agents such as DuPont FM-200, which have zero ozone depletion potential and are preferred alternatives to Halon, fulfills this requirement. In recent years, economic changes and increasing environmental awareness have led to many doubts and misinformation about the use of clean agent fire extinguishants, causing many to forego them entirely. The issues dealt with in this article attempt to dispel the inaccurate information that has circulated, but if you still have doubts ask anyone whose business has been saved by the successful discharge of a clean agent system.
A recent incident involving a clean agent system installed by Automatic Protection Limited (UK) provides a compelling case. The event involved the main communication room of a call centre in the Scottish Borders, following which the manager commented, ‘Who knows what the damage would have been had we not had the FM-200 system installed to kill the fire before it got started. This really demonstrates the value of the system, which all too often is looked on as a 'nice to have', rather than a necessity.