Suppression of fires

API Publ 2021A, Interim Study—Prevention and Suppression of Fires in Large Aboveground Atmospheric Storage Tanks, 1st ed., July 1998... 

Most organic compounds are water-insoluble. Notable exceptions are the lower molecular weight alcohols, aldehydes, and ketones, all known to be "polar" molecules. This characteristic is of importance to firefighting because the specific gravity of the compound will then be a major determinant of the suitability of water for the suppression of fires involving the chemical. 

Baraban, J. M., and Aghajanian, G. K. (1980) Suppression of firing activity of 5-HT neurons in the dorsal raphe by alpha-adrenoceptor antagonists. Neuropharmacology, 19 355—363. 

When water is combined with other additives, it can control and extinguish most petroleum fires. A water suppression system consists of a supply source, distribution system, and the end using equipment such as fixed spray systems, monitors, hose reels and hydrants. The objective of water suppression systems is to provide exposure cooling, fire control, suppression of fire incidents and may assist in the dispersion of flammable or toxic vapors. 

Sprinkler - Water deflector spray nozzle devices used to provide distribution of water at specific characteristic patterns and densities for purposes of cooling exposures, suppression of fires and vapor dispersions. 

Water mist systems are intended for rapid suppression of fires using water discharged into completely enclosed limited volume spaces. Water mist systems are desirable for spaces where the amount of water that can be stored or that can be discharged is limited. In addition, their application and effectiveness for flammable liquid storage facilities and electrical equipment spaces continues to be investigated with optimistic results. Water mist systems are also used for gas turbine enclosure protection. 

The generally accepted mechanisms for the suppression of fires and explosions by alkali metal salts such as potassium chloride, KCl potassium bicarbonate, KHCO3 and potassium carbonate,K2C03 in the form of dry powders or aerosols (smokes) involve heat absorption, endothermic decomposition and radical recombination. 

But the activation-only model and the unidimensional graphs are inadequate because they do not represent either the active suppression of sensory input and motor output that is essential to the maintenance of behavioral sleep in the face of the restituted electrical activation state of the brain or the complete suppression of firing by locus coeruleus and raphe neurons that causes the electrically reactivated to become aminergi-cally demodulated. 

Similarly to NE, DA also suppresses the firing activity of NE neurons, via the D2-receptor mediated mechanism. NE however has different effects on the firing activity of 5-HT and DA neurons the decrease in the brain NE followed by an increase of activity of DA neurons and by suppression of firing of 5-HT neurons (Guiard et al., 2008). Figure 7 summarizes the reciprocal interactions between NE, 5-HT and DA systems. 

Suppression of fires (e.g., sprinkler systems, gaseous extinguishing systems, using noncombustible materials in facility, restrict storage of combustible consumables such as paper)... 

The use of fire retardants in polymers has become more complicated with the realisation that more deaths are probably caused by smoke and toxic combustion products than by fire itself. The suppression of a fire by the use of fire retardants may well result in smouldering and the production of smoke, rather than complete combustion with little smoke evolution. Furthermore, whilst complete combustion of organic materials leads to the formation of simple molecules such as CO2, H2O, N2, SO2 and hydrogen halides, incomplete combustion leads to the production of more complex and noxious materials as well as the simple structured but highly poisonous hydrogen cyanide and carbon monoxide. 

Fire deteetion and suppression form the basis of fire eontrol, with emergeney baek-up proeedures to mitigate the eonsequenees. Seleeted key taeties for working with flammable ehemieals are summarized in Table 6.11. 

Density — the mass per unit volume of any substance, including liquids. The density of a liquid determines whether a spilled material that is insoluble in or immiscible with water will sink or float on water. Knowledge of this behavior is essential in checking whether to use water to suppress a fire involving the material. 

FIRE SIMULATOR predicts the effects of fire growth in a 1-room, 2-vent compartment with sprinkler and detector. It predicts temperature and smoke properties (Oj/CO/COj concentrations and optical densities), heat transfer through room walls and ceilings, sprinkler/heat and smoke detector activation time, heating history of sprinkler/heat detector links, smoke detector response, sprinkler activation, ceiling jet temperature and velocity history (at specified radius from the flre i, sprinkler suppression rate of fire, time to flashover, post-flashover burning rates and duration, doors and windows which open and close, forced ventilation, post-flashover ventilation-limited combustion, lower flammability limit, smoke emissivity, and generation rates of CO/CO, pro iri i post-flashover. 

A nonprofit organization that is the authoritative source for developing standards for minimizing the possibility and effects of fire and explosion conducts fire safety programs provides information on fire protection, prevention, and suppression develops systems for prevention and suppression offire and explosions arising from hazardous substances. 

Fire detection and suppression form the basis of fire control, with emergency back-up procedures to mitigate the consequences. Selected key tactics for working with flammable chemicals are summarized in Table 5.11. 

The acute CNS effects of MDMA administration are mediated by the release of monoamine transmitters, with the subsequent activation of presynaptic and postsynaptic receptor sites.40 As specific examples in rats, MDMA suppresses 5-HT cell firing, evokes neuroendocrine secretion, and stimulates locomotor activity. MDMA-induced suppression of 5-HT cell firing in the dorsal and median raphe involves activation of presynaptic 5-HT1A autoreceptors by endogenous 5-HT.4142 Neuroendocrine effects of MDMA include secretion of prolactin from the anterior pituitary and corticosterone from the adrenal glands 43 Evidence supports the notion that these MDMA-induced hormonal effects are mediated via postsynaptic 5-HT2 receptors in the hypothalamus, which are activated by released 5-HT. MDMA elicits a unique profile of locomotor effects characterized by forward locomotion and elements of the 5-HT behavioral syndrome such as flattened body posture, Straub tail, and forepaw treading.44 6 The complex motor effects of MDMA are dependent on monoamine release followed by activation of multiple postsynaptic 5-HT and DA receptor subtypes in the brain,47 but the precise role of specific receptor subtypes is still under investigation. 

There are various innovations that the fire science community can produce to reduce human losses. These include less flammable materials, early and accurate fire detection devices, and reliable suppression systems. Each of these approaches assists in keeping the fire from becoming large, an important factor since most fatalities in the United States occur some distance away from the room of fire origin from smoke generated from large fires (5). 

Neuropeptide Y (NPY) and its receptors may also be important in the regulation of anxiety and stress. NPY is synthesized in the arcuate nucleus, which receives LC input. In a number of rodent models, NPY administration has anxiolytic and, at somewhat higher doses, sedative effects. Likewise, NPY antagonizes CRH-induced stress responses, and suppresses LC firing when injected... 

---