Fire growth: No sprinklers

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Fire growth No sprinklers
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Fire growth Sprinklers present
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Workbook Page
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Why Fire Sprinklers?

• 80 of fire deaths occur in the home
• Low probability, high consequence event
• Over 4,000 people die each year in home fires
• millions in property damage
• Less than 2 of homes contain sprinklers

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Residential sprinkler benefits
Life safety
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Residential sprinkler benefits
Property safety
Conservation
Environmental impact
FF safety
Housing density
Demand on FD
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Causes of house fires ()
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25
15
13
22
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Who Is Most At Risk In A Fire?

• Sleeping occupants
• Small children and the elderly
• Twice as likely to die as able-bodied adults

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What Is Flashover?

• When ceiling temp reaches 1,200 F
• Bottom of smoky layer erupts into flame
• Everything combustible ignites at once
• Can take as little as five minutes

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Heat Spread by Convection
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Heat Spread by Convection
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Most victims in post-flashover fires are remote
from the room of origin
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Residential Sprinklers Demand on Resources

• Water
• 9-12 GPM v. 200 GPM per line.
• Apparatus personnel
• Fewer critical tasks fewer resources.
• Organization
• Can be EMS-oriented v. suppression-oriented.

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Critical fireground task

• A task that must be performed simultaneously, or
  in a highly coordinated manner, with other tasks.
• Examples of critical tasks
• Attack line and ventilation
• Attack line and water supply

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Critical Fireground Tasks

• Task Personnel Assignment
• Attack 2 1st
  engine
• S R 2 Ladder
  Co.
• Ventilation 2 As
  assigned
• Backup line 2 2nd engine
• Safety 1 As
  assigned
• Pump oper. 2 Each engine
• Water supp. 1 2nd engine
• Command 1 District
  chief

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Sprinkler v. manual suppression

• 30-90 seconds after flames
• 13 GPM _at_ 10 PSI
• Very little has burned
• Room of origin still tenable to life
• Operates automatically

• 8-15 minutes after report
• 200 GPM _at_ 100 PSI
• A lot has burned
• Entire home untenable to life
• Someone needs to call fire department

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Sprinkler v. fire department

• Sprinkler
• Operates whether you can take action or not
• Elderly, bedridden, children
• Operates whether you are there or not
• Asleep, in another room, in yard, away

• Fire department
• Firefighters cant respond until someone calls
• Fire can burn unnoticed until it breaks out of
  house

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Why sprinklers?

• Builders build safe homes then people move in
• Houses dont catch fire, contents do
• Contents loaded with synthetic material
• Burn twice as hot, twice as fast
• Homes are tight for energy

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Why FDs want sprinklers

• Cant respond in time to save lives
• Content fires go to flashover in 5 minutes or
  less
• Occupants start dying halfway to flashover
• Occupants who cant get out under own power twice
  as likely to die
• The young, elderly

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Smoke alarm limits

• In house fire where deaths occurred, over 40
  percent of the homes had working smoke detectors
• Occupants often disable smoke alarms to prevent
  nuisance alarms

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Sprinkler effectiveness

• Smoke detectors by themselves less than 50
  effective
• Smoke detectors sprinklers increase survival
  rates to 97
• Based on long-term studies in Napa CA, Prince
  Georges County MD, Scottsdale AZ

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Why sprinklers are effective

• Quick acting (30-60 seconds after flames visible)
• Fire is small and containable
• Stop spread of smoke and flame before flashover
• Control fire with 10-15 GPM v. 200 GPM from fire
  hose

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Sprinkler experience

• Zero lives lost in sprinklered homes
• Scottsdale, AZ
• Napa, CA
• Prince Georges County, MD
• Property damage (including water damage) nine
  times less
• Fire departments handle with fewer stations and
  firefighters

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Before 13D

• NFPA 13 was the only standard
• Categorizes buildings by hazard class
• Fire load, rate of heat release, peak heat
  release
• Uses area v. density to determine water flow
• As hazard class increases, density and coverage
  area increase
• Higher hazard more GPM, more sprinklers
• Additional gallonage for fire hoses

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NFPA 13 Area/Density curves
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Density and area coverage

• Function of orifice size and pressure.
• Orifice size indicated by K factor.
• Examples - 3.0, 3.9, 4.2, 5.6.
• The higher the K factor, the larger the orifice.

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Lower pressure smaller area
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Higher pressure larger area
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Use of higher pressure

• Sprinklers with the same orifice size can cover
  wider areas with the same density
• Reliable RES 16, 3.0 K factor
• 9 GPM over 12 x 12 area at 9 PSI
• 10 GPM over 14 x 14 area at 11.1 PSI
• Both supply .04 GPM per sq. foot

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Use of larger orifices

• Compared to a head with a smaller K factor, one
  with a larger K factor supplies a higher density
  to the same area.
• 3.0 for 14x14 area flows 10 GPM at 11.1 PSI.
• 3.9 for 14x14 area flows 12 GPM at 9.5 PSI.

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Hydraulically most remote

• The hydraulically most demanding
• At the minimum required flow, the sprinkler that
  causes the highest drop in pressure from the
  street
• Not the geographically most remote on gridded
  systems
• Water enters grid at different points

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NFPA 13D

• Installation of Sprinkler Systems in One- and
  Two-Family Dwellings and Manufactured Homes

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NFPA 13Ds beginnings

• America Burning published in 1973
• US leads in fire deaths.
• Most fire deaths occur in homes.
• NFPA 13 committee formed residential
  sub-committee to investigate sprinkler protection.

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Format of 13D

• 1 - General information.
• 2 - Water supply.
• 3 - System components.
• 4 - System design.
• 5 - Limited area dwellings.
• 6 - Referenced publications.
• App. A - Explanatory material
• App. B - Referenced publications.

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13D objectives

• Limit maximum ceiling temp to 600F.
• Limit temp at 5 3 to 200F.
• Prevent flashover and keep room of origin tenable
  to life for 10 minutes.
• Attain objectives with no more than two
  sprinklers operating, with density of .04 GPM/sq.
  foot.
• No minimum area requirement.

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Committee recommendations

• System can be slightly less reliable, with fewer
  operational features, and be effective
• Must be substantially less expensive
• Primary goal life safety
• Secondary goal property safety
• Should control fire for sufficient escape time
  10 minutes

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Recommendations

• Piping, components, hangers must be compatible
  with residential construction techniques
• Combined sprinkler/plumbing systems are
  acceptable from a fire protection standpoint
• Sprinklers can be omitted in areas of low
  incidence of fire deaths

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First edition of 13D in 1975

• Based on relatively limited scientific
  understanding of residential fires and how
  sprinklers should protect against them
• Applied technology that was applicable to
  property protection or commercial, industrial
  occupancies
• Was not cost-effective but spurred research and
  development

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Full scale tests

• Discharge rates
• Spray patterns
• Response sensitivity
• Design criteria
• Ability to maintain tenability to life for escape
  time

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Goal Tenability in room of origin

• Carbon monoxide concentration
• 3000 PPM
• Temperature at breathing level
• 200F
• Oxygen depletion

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1980 edition

• Based on better understanding of residential
  fires
• Had a new class of sprinkler
• Based on different method for calculating minimum
  water flow

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Criteria for residential sprinklers

• Prevent flashover.
• Turning point in fire for victims, firefighters
• Maintain 200oF at eye level
• Temperature is survivable near the floor
• 150oF of moist air will prevent breathing
• Control fire with one or two sprinklers
• Allows smaller water supply

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What Does NFPA 13D Say About Water Supply?

• Must have enough to meet demand for 10 minutes
• Acceptable are
• Connections to a reliable waterworks system
• An elevated tank
• A pressure tank
• A stored water source with an
  automatically operated pump

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Sprinkler incentives

• Narrower streets
• Smaller setbacks
• Smaller water mains
• Fewer fire hydrants
• Fewer fire stations

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WHAT LIES AHEAD
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10-20 GPM v. 200 GPM
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Fire threat, 1-2 family homes

• Sleeping occupants
• Small children, elderly and no special exit
  arrangements
• Cooking facilities
• Smoking
• Unprotected vertical openings

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House fires

• A low probability event, but a high-consequence
  event
• A reasonably expected risk in this community

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Flashover is the enemy

• Flashover - all exposed surfaces in room ignite
  almost simultaneously
• Flashover description - flames out the door of
  room of origin
• Time to flashover dictated by rate of heat
  release
• Synthetics burn twice as hot, twice as fast

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Time to flashover

• Measured from time of flaming stage
• A large portion of fires go to flaming stage
  quickly
• Smoldering stage nearly always progresses to
  flaming
• May not produce much hot smoke until shortly
  before flaming

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Fire cause and time to flashover

• Unattended cooking Very quickly
• (25-30 )
• Playing with matches Very quickly
• (13 )
• Arson (15) Very quickly
• Smoldering cigarette Minutes-hour
• (20-25)
• Heating (15) Minutes
• Electrical (10-12) Minutes-hour

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Most victims in post-flashover fires are remote
from the room of origin
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Home fires by victim location extent of flame
damage
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Residential Sprinkler Characteristics

• Fast response
• 30-60 seconds v. 120-180 seconds for commercial
  sprinklers
• Discharge pattern
• Hits wall at 12 below ceiling
• Prevents flashover in room of origin
• Reduces number of critical fireground tasks

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characteristics.

• Responds before room of origin becomes untenable
  to human life
• Tenability
• Eye-level temp gt 150oF, moist air
• CO gt 3000 ppm
• Smoke gt .5 Optical Density/m

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House fire at 4842 Oak Street

• Two-story home
• Fire in kitchen
• Source - Electric heater
• Material ignited - synthetic-lined drapes, spread
  to cabinets and cupboards

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Residential fires

• 23 of fires
• 80 of fire deaths
• 75 of fire injuries

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Events after discovery

• Family sleeping in upstairs bedrooms
• Parents awakened (maybe smoke alarm).
• Mother saw incipient fire, called 911
• Smoke, heat blocked mother from returning
  upstairs, she escaped through front door
• Father rescued two sons, could not reach third
• One fatality, four injured

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Fire growth

• Flashover occurred 4 minutes after flaming stage
• Untenable in 2 minutes
• Fire department arrived 4-5 minutes after call
• Victim died of CO poisoning

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Witness statements confirm model results

• Mothers description
• Saw curtains on fire
• Grabbed extinguisher, fire too large
• Went to living room to call 911
• Tried to go back upstairs, stopped by smoke/heat
• Neighboring firefighters description
• Saw fire in kitchen as he started across street
• In seconds, flames were out front door

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If sprinklers had been installed

• No sprinkler
• Untenability in 123 seconds (smoke, heat, O2)
• Flashover in 4 minutes, 8 seconds

• Sprinkler present
• Sprinkler operated in 68 seconds
• Ceiling temp 250F
• Not enough smoke, heat, CO to make room untenable