Fire Science Exam #1

Three most common types of fire extinguishers

1. Water (APW) - least common 2. Carbon Dioxide (CO2) 3. Cry chemical (ABC, BC, DC)

Combustible liquids have a flashpoint at or above ______ degrees.

100

Flammable liquids have a flashpoint at or below ______ degrees.

100

Moderate fire loading

100,000-200,000 Btu/ft2 applies to most industrial occupancies such as a machine shops and assembly areas. 2-hours of fire resistance

High fire loading

200,000-400,000 btu/ft2, this classification will cover warehousing of various products. 2-hour fire resistance is needed.

Atomsphere oxygen content is generally around ___%

21%

Hydrostatic testing is generally required for water and CO2 extinguishers every _______ years, and every ______ years for dry chemical models.

5 years, 12 years.

Below ____% oxygen, fire stops completely

8%

Low fire loading

<100,000 btu / ft2 generally applies to schools, offices, hotels, and most hospitals. 1-hour fire resistance is needed.

Ultra-high fire loading

>400,000 btu/ft2 flammable liquids will most likely fit into this particular classification.

Class A explosive

A detonating or otherwise maximum hazard; eg. black powder, dynamite, blasting caps

Corrosive chemicals in fire safety

A liquid or solid that causes visible destruction or irreversible changes in human skin tissue, or corrodes metal or other materials. Strong acids or alkalis are most common.

What does APW stand for

Air pressurized water

NFPA 10

All commercial vehicles must carry at least one fire extinguisher. Locations such as those storing and transporting pressurized flammable liquids or gas are required to be equipped with "fast flow extinguishers" by NFPA 10, depending on the amount of the liquid or gas.

What is a metal that burns easily in powder form, but not easily in solid?

Aluminum

One rule to keep in mind when fighting a fire with an extinguisher

Always keep your back to an exit in case you need to gtfo

What is ANSI and what do they do?

American National Standards Institute Private non-profit, that oversees the development of standards, and publishes a bunch of standards. MOST influencial standards org, solid standards NFPA has their standards published by ANSI, so ANSI publishes fire safety standards and fire safety codes

What is an oxidizer?

An active chemical that releases oxygen when burning which fuels the fire.

What is the basic measurement of a fire load?

British thermal units (Btu's), or the amount of heat it takes to raise one pound of water one degree Fahrenheit.

Class B fire & how to extinguish

Burnable fuels such as gasoline, oil, or alcohol Extinguished with CO2 and dry chemicals to inhibit the chain reaction, or restrict oxygen - No water

Thermoplastic resins

Can be repeatedly softened and hardened by heating and cooling, without a chemical change taking place. ex: polyethylene, polyvinyl chloride. Lower ignition temperature than thermosets, and generate more smoke (more hazardous).

Thermosets

Can melt and take shape once, after they solidify they stay solid. Used on electrical equipment because they are less flammable.

Class D Fire and how its extinguished

Combustible metals like magnesium, sodium, titanium, powdered aluminum, potassium, and zirconium Extinguishing agents - Specialized fire extinguishers

Where might a dry chemical fire extinguisher be found?

Commercial kitchens, and areas with flammable liquids

What are three ways of heat transfer?

Conduction: Two objects touch each other and heat gets transferred from high temp body to low temp body Radiation: Heat is transferred through the electromagnetic waves (Infrared light) Convection: Heat is transferred in circulating medium (either liquid or gas)

DOT

Department of transportation Enforces fire regulations, concerning shipment of hazardous materials by road, air, water, and pipeline.

What to extinguish with APW extinguishers and where they may be found

Designed for Class A fires only: Wood, paper, cloth APW's will be found in older buildings, particularly in public hallways Used in hospitals because they are harmless and non-contaminant.

What is the flammable / combustible classification system primarily used for?

Detemrining the degree of hazard and so appropriate code requirements for storage, transportation, use and protection. In short, to determine degree of hazard and implement appropriate fire prevention measures.

What does the NFPA do?

Develop and publish fire safety codes (about 300 codes) Consensus standards - voluntary standards Updated every 3 years Consists of member's of government agencies, organizations, and fire safety professionals

What to consider when building a flammable / combustible liquid storage area.

Drainage / secondary containment, ventilation, explosion proof electrical equipment, proper doors, fire suppression, controlling static energy.

How do we control the chemical reaction of a fire?

Dry chemicals are most common (in fire extinguishers)

Why are flashovers more common nowadays?

Due to carbon based building materials which burn faster and release more heat.

Class C Fire & how extinguished

Electrical Fire same as class a or b fire

What are some proactive measurements to prevent the fire from occurring?

Eliminate the fire hazards, or segregate fuel from the heat

What is a fire, and what three variables are needed to initiate a fire?

Fire is a chemical reaction that gives off heat and light The variables needed are Fuel+Oxygen --> Heat and Light = combustions byproducts (CO2 and CO) The basic idea for fire prevention is to prevent one of these 3 factors from happening

Fire load equation

Fire load = fuel weight x btu / area

What is the difference between flammable and combustible liquids?

Flammable - more dangerous because flammable liquids have a lower flashpoint.

What is the fire tetrahedron?

Four variables that sustain a fire Heat, Fuel, Chain Reaction, Oxygen. To put out a fire one of these variables needs to go bye bye.

Class B explosive

Function by rapid combustion rather than detonation. Special fireworks, flash powders

Labor Dept of OSHA

In charge of fire safety in workplaces, enforces regulations. Adopted old NFPA fire codes

Where are C02 extinguishers generally found and what part of the tetrahedron do they eliminate?

In laboratories, mechanical rooms, kitchens, and flammable liquid storage areas. These extinguishers smother fire fire by restricting oxygen. It also cools the fuel.

Where should large amounts of flammable / combustible liquids be stored?

In remote areas, away from process operations or public areas.

Monthly inspections of fire extinguishers should include:

It's in its designated place, no obstruction, operating instructions on nameplate, tamper seal is not broken or missing, no obvious physical damage, corrosion, leakage, or clogged nossle.

What are the most important conditions that regulate the combustibility of a metal?

Its form and shape. More surface area = more hazard.

Water (APW) Fire extinguisher

Large silver extinguisher, about 2 feet tall and contain 2.5 gallons (9 liters) of water. Filled with ordinary tap water and pressurized with air. These take the heat element out of the fire tetrahedron

What are required safety devices on above ground storage tanks?

Leak detection system, emergency venting (relief valve), pressure meter, special inspection

What must a safety can include?

Leak proof, automatically vent excessive pressure, filling and dispensing opening with auto close lids, must be clearly marked w contents.

Which is more dangerous heavy or light oil, and why?

Light oil, because it more easily produces vapor (lower flashpoint) ex. gasoline, diesel

Unstable chemicals

Likely to react with themselves violently (decompose or polymerize) when in an unstable condition such as high temperature, violent impact, or when involved in a fire; ex: acetaldehyde nitromethane

Which is more dangerous, a higher or lower flashpoint?

Lower flashpoints are more dangerous, as it is easier for the liquid to produce vapors, making it more volatile.

Class C explosive

Materials that do not ordinarily detonate in restricted quantities-minimum explosion hazard eg. flares, small arms.

What is flashpoint?

Minimum temperature in which a liquid produces sufficient vapors to be ignited in the presence of a heating source.

What is one of the best refrences for detailed requirements of fire safety?

NFPA 30

What type of fire extinguisher should be used on metal / metal powders?

NOT any common fire extinguisher. The extinguisher must be specific to the metal that is burning.

NFA

National Fire Academy Provide training to fire service personnel (fire fighters, fire officers) (gov't sponsored) Some of their curriculums include: Management science curriculum, haz mat, and fire prevention.

NFPA

National Fire Protection Agency Most influential (non-profit) organization regarding fire in the world with about 80,000 members worldwide

What are some common oxidizers?

Nitric acid, bromine, peroxides, chromates, ozone, and pure oxygen (the last two are very reactive oxidizers).

Is venting of a flammable storage cabinet recommended?

No

Should strong acids be stored in metal drums or metal cabinets?

No - strong acids react with metal and produce heat.

Can we store acids and alkali's together?

No - they will react with eachother to produce a lot of heat, causing fire.

Smoldering Phase of a Fire

Phase 1 - Oxygen is consumed when the concentration is below 15% Room / compartment temperature - still very high (up to 1300 degrees). Survival is difficult Backdraft - oxygen driven. When oxygen is introduced to smoldering fire and it starts back up.

What does PASS stand for?

Pull Aim Squeeze Sweep

Dry Chemical fire extinguishers

Put out fire by coating the fuel in a thin layer of dust which separates the fuel from the oxygen in the air. Usually red, range from 5-20 pounds

Carbon dioxide fire extinguishers

Red cylinders from 5-100 pounds or larger. Designed for class B and C fire only!

How do we control the fuel to put out a fire?

Remove it or contain it

Dept of Agriculture

Responsible for the fire safety of almost 200 million acres of national forests and grasslands.

What needs to be in place for above ground storage tanks?

Site security, lightning protection, vehicle impact protection, secondary containment, sprinkling system to cool tank during the summer.

How do we control the oxygen to put out a fire?

Smother the fire - fire extinguishers with a chemical foam, or CO2

Common Ignition sources in the workplace

Sparks, heating and cooling, welding, stove, electrical arcs, smoking, lighting and static electricity.

What can oxidizing chemicals do to a fire?

Speed up the devleopment of a fire and make it more intense. Cause substances that do not normally burn readily in air to burn rapidly. Cause combustible materials to burn spontaneously without the presence of obvious ignition sources such as a spark or flame.

What is appropriate for buildings occupied for storage, processing, and manufacturing of combustibles of flammables such as those involved in the plastics industry?

Sprinkler protected, non-combustible construction, as well as extinguishers.

What are reactive measures for fire protection?

Sprinkler systems, and fire extinguishers

Incipient stage of a fire

Stage 1 - Fire which is in the initial or beginning stage, best stage to attempt extinguishing by portable fire extinguisher. growing stage, but still room temp

Free-Burning Stage of fire

Stage 2 - Fuel and oxygen are consumed quickly, room temps can be higher than 1300Deg F, flashover may happen

Flashover

Stage of a fire at which all surfaces and objects within a space have been heated to their ignition temperature, and flame breaks out almost at once over the surface of all objects in the space.

Define Fire loading

The amount of fuel available to the fire. It is a measure of the maximum heat that would be released if all of the fuels (combustibles) in a given area burned. The fire load indicates the fire intensity in case a fire happens.

What is the flammable liquid classification system based on?

The flashpoints of the various liquids.

NFPA's definition of ignition

The minimum tamperature required to initiate or cause self-sustained combustion independently of the heating or heating element. Or, anything flammable will burn spontaneously at a certain temperature without an external ignition source.

The higher the fire load, the

The more heat would be released if fire happens.

What is the flammable, or explosive range?

The range of a concentration of a gas or vapor that will burn (or explode) if an ignition source is introduced. From the LEL to the UEL

Boiling Point

The temperature at which the vapor pressure of a liquid is equal to the external pressure.

Two classes of combustible plastics

Thermoplastics and thermosets

Air reactive and water reactive chemicals

These chemicals may heat spontaneously, ignite, yield toxic or flammable gases, or react violently when exposed to air or water. Included are chemicals such as carbides, and phosphides.

How do insurance companies effect an organizations fire safety?

They provide consulting services

US Forest Service

This division of the Dept of agriculture is in charge of fire safety by protecting and doing research on forest fires.

Toxic Chemicals

Toxic gas or vapor produces during chemical reaction due to exposed to fire can harm firefighters health. Some of the highly toxics are immediatly dangerous to life and health at low concentrations in the air.

Who must a safety can be approved by?

UL or FM

What is UL and what do they do?

Underwriters laboratories Operate the laboratories for testing products, provide certification service for products like fire extinguishers, fireproof cabinets, and safety cans

USFA

United States Fire Administration Under the department of homeland security's federal emergency management agency. Non regulatory agency that provides public education and fire safety training. They also provide funding to do fire safety research, and compile and publish data on fire safety.

When does a free-burning fire stop and start smoldering?

When the oxygen content falls below 15%

The safest way to store flammable / combustible liquids is to store them __________________.

in a seperate shed or building.

Oxidizing chemicals

includes liquids or solids that readily give off oxygen or other oxidizing substances (bromine, chlorine, fluorine, and intensifies the combustion of other materials. This increases the chance of a fire or explosion.

Class A fire & how extinguished

ordinary combustibles like wood, paper water (most common), foam, dry chemicals (interrupt reaction)

Fire triangle is for ____________, while the fire tetrahedron is for ___________ the fire.

prevention, extinguishing

How do we control the heat to put out a fire?

water