Andrew K. Kim

A Closer Look At The Fire Extinguishing Properties Of Water Mist

Fire suppression with water mist is widely considered to be an alternative to gaseous fire suppression agents. Much commercial activity has occurredin the last 5 years to develop technology for fire suppression systems based on water mist. Although researchers in the 1950s recognized the dominant mechanisms of extinguishment, recent experimental work has improved the understanding of the extinguishing properties of water mist. This paper proposes a classification terminology for water mists to facilitate discussion of water mist systems. It describes the primary mechanisms of extinguishment, namely heat extraction, oxygen displacement, and radiation attenuation, and invokes theoretical considerations of vapourlair mixture dilution and kinetic effects at the molecular level. Evidence of an effect of invigoration of combustion caused by the introduction of water mist is presented. Not all fires are extinguished rapidly by water mist: the time to extinguish a fire is a function of fuel type, geometry and mist characteristics. An understanding of the suppression properties of water mist allows a designer to make reasonable choices in designing a suppression system for a particular fire scenario, and is essential for the development of algorithms for computer models of water mist suppression systems.

Multipurpose Overhead Compressed-Air Foam System and Its Fire Suppression Performance

This paper describes a newly-developed compressed-air foam (CAF) system, based on an overhead fixed-pipe installation, and presents results showing its fire suppression performance. The CAF system generates foams by injecting compressed air into the flowing foam solution. The resulting foam is characterized by excellent fire-mitigation properties. This is because compressed-air foams, at the expansion ratios of between 1:4 to 1:10, consist of very small and uniform-in-size air bubbles. The system needs little water to operate and is able to provide effective protection against Class A and B fires. The systems performance was compared to the performance of water mist and sprinkler-based installations. The experiments confirmed that the CAF system is effective in suppressing Class A and B fires. For the scenarios evaluated, the compressed-air system generated foams with sufficient momentum to penetrate the fire plume and to reach the fuel surface. The experimental results indicate that, in an open space, the foam system performs much better than water mist in extinguishing wood crib and flammable liquid pool fires. In an enclosed space, both water mist and compressed-air foam perform equally well against flammable liquid fires. The suppression performance of the CAF system on large wood crib fires was much better than a sprinkler system.

Brillouin Scattering Based Distributed Fiber Optic Temperature Sensing For Fire Detection

This paper presents a distributed fiber optic Brillouin scattering investigation, which involves measuring the Brillouin intensity versus time for real-time temperature measurements. This can be applied in practical fire detection schemes through the use of a threshold temperature that corresponds to the maximum Brillouin intensity. In the experiments, a 11 km fiber length was interrogated by 20 ns pulses (2 m spatial resolution) to monitor the temperature variations in a 10 m fiber region. The corresponding theory has confirmed the suitability of real-time intensity monitoring for temperature measurement.

Full-Scale Evaluation of Halon Replacement Agents

Full-scale fire suppression testing of HFC-227ea and HCFC Blend A was conducted in a 121 m3 compartment. HFC-227ea was tested at 7.6 and 8.8%; HCFC Blend A was tested at 8.6, 9.3, 10, 12 and 14% (by volume). Information on discharge characteristics and fire suppression performance of these halon replacement agents was obtained. HFC-227ea extinguished all test fires at the test concentrations. HCFC Blend A extin guished all test fires only at test concentrations of 12% or higher. These two agents produced halogenated acid gases whose quantity depended on the type, concentration and discharge of the agents and the size of the test fires. Language: en

Review of Total Flooding Gaseous Agents as Halon 1301 Substitutes

This paper provides a review of total flooding gaseous agents as Halon 1301 substitutes. Agents are compared, based on published data, in terms of their environmental impact, toxicity, fire suppression performance, and acid gas production from small-to full-scale tests. These data are also collected in tables. Acceptability of an agent by regulatory authority is mostly determined by agent toxicity. Based on the toxicity criteria set by the U.S. Environmental Protection Agency (EPA), five commercial halocarbons (FC-218, FC-3-1-10, HFC-23, HFC-227ea, and HCFC Blend A) and three commer cial inert gases (IG-01, IG-55, and IG-541) are acceptable for total flooding in normally occupied spaces. They are less effective by weight or volume than Halon 1301, with additional limitations and weaknesses. Language: en

Application of Water Mist to Extinguish Large Oil Pool Fires for Industrial Oil Cooker Protection

Large oil fires occurring in industrial oil cookers are very challenging to extinguish due to their size and the large amount of hot oil involved. This paper reports a study to use water mist for large industrial oil cooker protection. The extinguishing mechanisms of water mist and corresponding criteria required for extinguishing large pool cooking oil fires were investigated both theoretically and experimentally. Based on the extinguishing mechanisms and required criteria, two water mist systems were developed in the present work. A series of full-scale fire tests were conducted in a large industrial oil cooker mock-up. The study showed that the two water mist systems presently developed worked effectively to extinguish large cooking oil fires and prevented them from re-igniting. Their extinguishing performance was determined by the type of water mist system, discharge pressure and hood position in the oil cooker.

Production Of Carbon Monoxide During Fire Suppression Using Halon Replacements

During full-scale fire suppression tests, halon replacement agents (HFC-227ea and HCFC Blend A) were observed to produce an increased quantity of carbon monoxide (CO), in addition to the production of halogenated compounds. Agent-flame interaction resulted in the increased CO production in the fire tests. CO inhalation has been considered as an important cause of incapacitation in many fire incidents. Therefore, future risk assessment of potential exposure to toxic gases generated during fire suppression using halon replacements should include not only the toxic effect of halogenated compounds but also the toxic effect of CO and their combination.

Corrosion of Electronic Components by Hydrogen Fluoride

Generation of hydrogen fluoride (HF) from fire suppression by some gaseous agents is a major concern, because HF causes corrosion. Without proper precautions, the HF corrosion damage to some electronic facilities can be significant. A study has been carried out to evaluate the corrosion effect of HF on electronic equipment. This article describes details of the corrosion study in terms of test results from corrosion damage assessments. Test results show that surface corrosion on the electronic boards is visible when the test specimen is exposed to HF concentrations above 1000 ppm for 1 h. Test results also show that a video card with many attached components is much more vulnerable to HF corrosion damage than other test boards. The functionality of the video card is affected even at a relatively low HF concentration of 500 ppm.