Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: retention time; hold time; total flooding; clean agent; validation study. Includes bibliographical references (leaves 52-54).

Full-scale experiments are conducted to study the effects of different water-based indirect and combination initial attack methods on the compartment environment and firefighter during compartment fire suppression, with an aim toward improving manual fire suppression effectiveness and firefighter safety. Hot layer temperatures typical of room fire conditions are developed in the test compartment using wood cribs. Five suppression methods including straight stream, penciling, continuous wide and narrow fog, and a wide angle burst method are examined for two different spray angles and nozzle pressures. Temperatures, heat flux, gas velocity, and gas concentrations are monitored for the duration of each experiment in the fire compartment, along with temperatures and gas concentrations in the area of the firefighter, just outside the compartment. Realistic fire conditions are repeatedly established in the test compartment, with each fuel load allowing up to nine suppression applications per fire. The repeatability of the compartment temperatures are demonstrated by the consistent hot layer temperature stratification in the room, along with the uniformity of the hot layer throughout a test, and the consistency of the temperature from test to test. The repeatability of each suppression method is also demonstrated by comparing results of compartment cooling achieved in repeat tests. Differences in average compartment temperature before and during suppression indicate that penciling tactics provide little cooling of the compartment. In narrow fog attacks, the hot layer is pushed toward the floor, resulting in increased temperatures in the lower layer, generally an undesired result. Wide angle fog methods may have greater impact on compartment temperature as compared to straight stream or narrow fog methods, however, they also result in large increases in temperature at the firefighter. Wide angle burst tactics less effectively cool the compartment gases than continuous methods, but also lead to less impact on the firefighter. Greater numbers of bursts increase cooling of the compartment, but at the expense of increased impact on the firefighter. Including impact on the firefighter, continuous straight stream methods, at a nozzle discharge pressure of 700 kPa and aimed to the top of the rear compartment wall, appear the best choice for initial attack on the fire developed in these experiments. Due to variability between real fire scenarios and experiments such as these, significantly more study of the various suppression tactics is required before the most effective methods of suppression can be determined for a given set of fire scenarios.

Full-scale experiments are conducted to study the effects of different water-based indirect and combination initial attack methods on the compartment environment and firefighter during compartment fire suppression, with an aim toward improving manual fire suppression effectiveness and firefighter safety. Hot layer temperatures typical of room fire conditions are developed in the test compartment using wood cribs. Five suppression methods including straight stream, penciling, continuous wide and narrow fog, and a wide angle burst method are examined for two different spray angles and nozzle pressures. Temperatures, heat flux, gas velocity, and gas concentrations are monitored for the duration of each experiment in the fire compartment, along with temperatures and gas concentrations in the area of the firefighter, just outside the compartment. Realistic fire conditions are repeatedly established in the test compartment, with each fuel load allowing up to nine suppression applications per fire. The repeatability of the compartment temperatures are demonstrated by the consistent hot layer temperature stratification in the room, along with the uniformity of the hot layer throughout a test, and the consistency of the temperature from test to test. The repeatability of each suppression method is also demonstrated by comparing results of compartment cooling achieved in repeat tests. Differences in average compartment temperature before and during suppression indicate that penciling tactics provide little cooling of the compartment. In narrow fog attacks, the hot layer is pushed toward the floor, resulting in increased temperatures in the lower layer, generally an undesired result. Wide angle fog methods may have greater impact on compartment temperature as compared to straight stream or narrow fog methods, however, they also result in large increases in temperature at the firefighter. Wide angle burst tactics less effectively cool the compartment gases than continuous methods, but also lead to less impact on the firefighter. Greater numbers of bursts increase cooling of the compartment, but at the expense of increased impact on the firefighter. Including impact on the firefighter, continuous straight stream methods, at a nozzle discharge pressure of 700 kPa and aimed to the top of the rear compartment wall, appear the best choice for initial attack on the fire developed in these experiments. Due to variability between real fire scenarios and experiments such as these, significantly more study of the various suppression tactics is required before the most effective methods of suppression can be determined for a given set of fire scenarios.

Fire suppression in the southern and central Appalachian Mountains has resulted in an alteration to vegetation structure and composition. For this research the dominant species, abundance, density and age structure of the ericaceous shrub layer is characterized on four sites across the southern and central Appalachian Mountains. Fire histories for each of the sites varied, and were determined in previous research using dendroecological techniques. Over 800 ericaceous shrubs were collected, species included Pieris floribunda (Pursh) Bentham & Hooker f., Rhododendron maximum L. and Kalmia latifolia L.. Basal area of ericaceous shrubs was significantly different between sites. Age structures show that when fire suppression started Ericaceae began to establish. A few Ericaceae cross-sections displayed scars, that are likely associated with fire events, suggesting they probably survived mild fire events. Ericaceous shrub age structures were also compared to SPB outbreaks and PDSI. There were no significant correlations, but field observations suggest that SPB may be providing conditions suitable for Ericaceae establishment. Topographic patterns reveal that Kalmia latifolia is most abundant at mid-slope positions and decreases at higher and lower slope positions. There were significant differences in the density between slope positions averaged across all sites. Sites with the most recent and frequent fires did not have any of the three ericaceous shrubs collected at the slope bottom or ridge-top. At the most fire-suppressed site Ericaceae are present at every slope position. Age structures reveal that the oldest Ericaceae are found at the mid-slope positions while the age of thickets appears to decrease away from the mid-slope position. This pattern suggests that Ericaceae are moving into slope positions where they were previously less abundant. Sites with the most recent frequent fire regime seem to have prevented Ericaceae from heavily inhabiting high and low topographic positions while also reducing the overall basal area and density of Ericaceae.

In the absence of canopy-opening disturbances, upland oak forests in the eastern United States are shifting to shade-tolerant, fire-sensitive tree species (i.e. mesophytes) via a hypothesized positive feedback loop of less flammable, self-promoting conditions, termed mesophication. To evaluate species-specific impacts on mesophication, I quantified canopy, bark, and leaf litter traits of five hypothesized mesophytes [red maple (Acer rubrum), sugar maple (A. saccharum), American beech (Fagus grandifolia), hickory (Carya spp.), and tulip poplar (Liriodendron tulipifera)] and four upland oaks [black oak (Quercus velutina), chestnut oak (Q. montana), scarlet oak (Q. coccinea), and white oak (Q. alba)] in central Kentucky. Red maple, sugar maple, and American beech had increased canopy depth with stem size, smoother bark, and small, thin leaves when compared to oaks. My findings suggest that some mesophytes, such as red maple, sugar maple, and American beech, may decrease future forest flammability by reducing understory light and increasing fuel moisture.

Active fire protection systems are an essential fire safety management tool, particularly in potentially high financial and risk consequence scenarios. In the UK and Europe over recent decades regulatory changes have been successful in creating an environment in which more innovation can take place. Increased numbers of fixed firefighting system types are now available to the user. However, not all systems offered are equal in terms of; suitability, cost, maturity of supporting knowledge, and overall performance or in-service reliability. Understanding of the systems performance and its limitations and how to match this to the assessed fire risk is incomplete among users. Experts are observing increasing numbers of what they consider to be poor fixed firefighting system choices leading to weaker fire safety designs, which is a cause of concern. Therefore the research aim is to verify that these concerns are founded and, that being the case, to develop a decision support system and related supporting resources to further this aspect of fire safety education and enable users to make better informed system selections. Thus, the focus of this research has been to develop a fixed firefighting system selection tool to complement existing legislation, which incorporates logic, rules and fire safety educational resources in a variety of formats to aid the fire safety design process. A variety of largely heuristic techniques have been used to aggregate data to form knowledge to underpin fixed firefighting system selection tool. In this form, the tool has been validated by experts as being a useful resource. The developed tool also provides ample opportunity for useful ongoing future development. The work recognises that cost and benefit are critical in the selection process. Supporting resources have been incorporated into the tool to assist users in evaluating the levels of reliability they might expect from a system in their circumstances. This tool has now been exposed to a wider audience of experts as part of an evaluation process. Findings include: that the tool is an innovative approach to promoting good fire safety designs, the tool efficiently provides useful fire safety education to users and the developed supporting resources which consider firefighting system reliability are helpful. This thesis and reference papers summarise the key stages of this research and tool development. The thesis concludes by outlining the progress achieved by this work and recommendations arising.

The onset of fire within a compartment can pose a hazard to the occupants and the structure containing the compartment. Fire suppression systems aim to either extinguish or suppress an incipient fire before loss of life or damage to the structure can occur. The geometry and use of the compartment as well as the fuel packages within must be taken into account when choosing an appropriate fire suppression system. This thesis explores novel suppression methods inside of compartments. Los Alamos National Laboratories came to the University of Texas Fire Research Group (UTFRG) to characterize and investigate the fire danger inside of nuclear gloveboxes. The first suppression method discussed explores activation tests of a commercial automatic fire suppression system (Fire Foe [superscript TM]) containing heptaflouropropane (FE-36) fire suppressant conducted within a glovebox at the UTFRG's burn structure. Temperature and time to activation data of ten tests at four different fire sizes, three 13 kW, one 20 kW, three 25 kW, and three 50 kW, was taken. Gas temperatures from experiments were compared against NIST's Fire Dynamics Simulator (FDS) gas temperatures with good agreement. The time and spatially averaged net heat flux on a virtual Fire Foe [superscript TM] tube from the FDS simulations were passed to a thermo-physical, semi-empirical, sub-model to predict activation with poor agreement from experimental activation times. A Bayesian parameter inference was later run on the sub-model. While the Bayesian inference approach is able to match sub-model temperatures to experimental temperatures, some non-physical values for heat transfer coefficients and view factors were observed at the lower heat release rate fires. Micro combustion calorimetry (MCC) was used to determine heat of combustion of glovebox glove material and cone calorimetry tests were run to find ignition time versus incident heat flux. Using standard ignition time models, effective model parameters were calibrated. Thermal characterization of the glove material showed that the heat of combustion found from MCC was within the range of heats of combustion for other non-halogenated materials found in the literature. Analysis of the time to ignition tests showed that the glove material should be modeled as thermally thick when one would expect thin behavior. This behavior was attributed to possible heat losses from the back of the glove material. Dry water is expected to have similar suppression characteristics as water mist systems because the dry water particle sizes are on the order of water mist droplet sizes. The major benefit with dry water is the low pressures needed to drive the aerosol. An issue encountered with the dry water was flowing it in the way one would flow normal water. It was found that at low normal and shear stresses, the dry water clathrates would release the water held inside. A possible low shear delivery mechanism was discussed that avoids the ratholing effect. A continuous dry water production system was also designed. Filter loading tests were conducted to determine the quality of the dry water collected from the batch and continuous cases. It was observed that the ratio of water to silica for the continuous case reaches the batch value and is similar to results found in the literature. For the batch dry water it was observed that the particle size of the dried clathrates does vary with rotational speed of the blender and is independent of the type of water used (tap or deionized). / text

This thesis includes three studies. The first study examined how reductions in light availability and changes in soil chemistry that occur as conifers establish in aspen stands, differentially affects the regeneration success of aspen and conifers. We found that aspen were more sensitive to changes in light and soil then subalpine fir. For aspen, reduced light and conifer influenced soils significantly reduced height, biomass, photosynthesis and the production of secondary defense compounds. Subalpine fir seedlings were significantly reduced in photosynthesis, biomass and R:S under lower light conditions but showed no differences in physiology or growth when grown on the contrasting soil types. Subalpine fir seedlings were significantly reduced in photosynthesis, biomass and root:shoot ratio under lower light conditions but showed no differences in physiology or growth when grown on the contrasting soil types. Results from this study suggest that reduction in light and changes in soil chemistry associated with conifer succession place constraints on aspen growth and defense capacity, which may contribute to losses in aspen cover under longer disturbance return intervals. The second study looked at regeneration dynamics of aspen and conifers as forest stands transition from canopy gaps to aspen dominated canopies to conifer dominated canopies. We found that as overstory conifer density increases, aspen decrease in density, basal area, and seedling establishment. Conifers were shown to establish closer to aspen as the canopy increased in conifer density. As this proximity relationship extended into the canopy there is increased mortality in both aspen and subalpine fir, suggesting both facilitation and competition. Our third study looked at the physiological effects of smoke exposure on growth and primary and secondary metabolic responses of deciduous and conifer tree species. Twenty minutes of smoke exposure resulted in a greater than 50% reduction in photosynthetic capacity in five of the six species we examined. Impairment of photosynthesis in response to smoke was a function of reductions in stomatal conductance and biochemical limitations. In general, deciduous species showed greater sensitivity than conifer species. Smoke had no significant affect on growth or secondary defense compound production in any of the tree species examined.

In historically fire-dependent upland oak forests of the eastern U.S., anthropogenic fire exclusion is likely causing a hypothesized feedback loop between an increase in fire-sensitive species and self-promoting, fireree conditions at the detriment of oak regeneration. This study determined how shifts from oaks (Quercus stellata and Q. falcata) to fire-sensitive non-oaks (Carya spp., Liquidambar styraciflua, and Ulmus alata) affected flammability and related processes that consequently determine species composition. Using treatments of increasing non-oak leaf litter, experimental burns were conducted and flammability measured under field conditions, and a laboratory litter moisture desorption experiment was conducted. As litter composition shifted from oak-dominated to non-oak-dominated, flammability decreased (R2 = 0.59, P < 0.001) and moisture-holding capacity increased (R2=0.88, P<0.001). To prevent further shifts toward fireree conditions and loss of economically and ecologically valuable oaks, prescribed fire should be reintroduced soon while oak maintains overstory dominance and controls forest flammability.

This work presents a solution for a real-time fire suppression control system. It also serves as a support tool that allows creation of virtual ship models and testing them against a range of representative fire scenarios. Model testing includes generating predictions faster than real time, using the simulation network model developed by Hughes Associates, Inc., their visualization, as well as interactive modification of the model settings through the user interface. In the example, the ship geometry represents ex-USS Shadwell, test area 688, imitating a submarine. Applying the designed visualization techniques to the example model revealed the ability of the system to process, store and render data much faster than the real time (in average, 40 times faster).