How To Put Out A Candle Fire

This answer is provided by William L. Grosshandler, leader of the Fire Sensing and Extinguishment Group in the Building and Burn down Research Laboratory at the National Institute of Standards and Engineering science (NIST).

extinguishers protect against small fires

HANDHELD extinguishers protect against pocket-size fires.

Fire extinguishers contain different chemicals, depending on the application. Handheld extinguishers, which are commonly sold at hardware stores for utilize in the kitchen or garage, are pressurized with nitrogen or carbon dioxide (CO_two) to propel a stream of fire-squelching agent to the fire. The active material may be a powder such equally potassium bicarbonate (KHCO₃), liquid water, an evaporating fluorocarbon or the propelling agent itself. The most effective and common fluorocarbon used until recently for this application had been bromochlorodifluoromethane (CF₂ClBr), referred to as halon 1211. By international agreement, still, production of all types of halons ceased in 1994 considering the bromine and chlorine atoms in the chemical were constitute to migrate over time to the stratosphere, where they react to deplete ozone in a very efficient catalytic bicycle.

Many fire extinguishing systems are built into the building or other structure being protected. H2o sprinklers are by far the most common type of fixed system because they are inexpensive, highly reliable and safe for people. But water damage cannot always exist tolerated (say, in a estimator room); information technology is sometimes ineffective (a fuel storage arrangement); and it is impractical where weight and space are limited (in an airplane). In these situations, fire extinguishers use dissimilar materials--ones that inundation a protected compartment with a burn-fighting gas. CO_two works well, but is fatal at the concentrations necessary to extinguish a fire, and so cannot be used where people will be present. Bromotrifluoromethane (CF_iiiBr, or halon 1301) is a close cousin to halon 1211, but has a much lower boiling point and toxic level--properties that have made halon 1301 the firefighting chemical of choice for applications where sprinklers cannot be used.

The phaseout of halons has led to a scramble by government and industry researchers to find environmentally suitable replacements. None have been identified with all the positive qualities of halon 1211 and halon 1301. The trick is that the bromine and chlorine atoms in the halon molecule--the very ones that are so dissentious to the stratospheric ozone--are too incredibly aggressive scavengers of hydrogen atoms, which are key to maintaining a combustion chain reaction. Indeed, bromine and chlorine atoms are released as halons decompose in the estrus of the burn down, establishing a catalytic cycle involving HBr and HCl; the cycle converts active hydrogen atoms to stable H_ii molecules, breaking the chain reaction.

Manufacturers have introduced new families of chemicals containing no chlorine or bromine, called hydrofluorocarbons (HFCs),that take physical properties like to the halons and no ozone depletion potential. But lacking Br or Cl atoms, the HFCs cannot disrupt the combustion reaction to the same caste. HFCs extinguish fires in a manner similar to CO_ii or Northward₂ --by absorbing heat and reducing the concentration of oxygen. Even so, several dissimilar companies are marketing such HFCs as CHF_iii, C₂HF_v, and C₃HF₇ for a diversity of applications.

The need to observe halon replacements remains. Researchers are actively pursuing various materials--including iron- and phosphorous-containing compounds and hydrofluorocarbons--with the ability to inhibit flames. They are also developing ameliorate means of discharging more than conventional chemicals, such every bit H_iiO, N₂ and CO₂ . For example, one idea is to apply a solid propellant to generate an inert gas mixture--an arroyo identical to the systems in car air bags. Such a organization, when activated, would extinguish a fire but equally one blows out a candle.

Source: https://www.scientificamerican.com/article/what-chemicals-are-used-i/