Fire growth: No sprinklers. Workbook Page 2 Fire growth: Sprinklers present.
-
Upload
cordelia-harrington -
Category
Documents
-
view
286 -
download
15
Transcript of Fire growth: No sprinklers. Workbook Page 2 Fire growth: Sprinklers present.
Fire growth: No sprinklers
Workbook Page2
Fire growth: Sprinklers present
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
Residential sprinkler benefits
Life safety
Residential sprinkler benefits
Property safetyConservationEnvironmental impact
Demand on FDFF safetyHousing density
Causes of house fires (%)
CookingMatchesArsonCigsHeatingElec
15
10
25
13
1522
Who Is Most At Risk In A Fire?
Sleeping occupants Small children and the elderly
Twice as likely to die as able-bodied adults
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
Heat Spread by Convection
Heat Spread by Convection
Most victims in post-flashover fires are remote from the room of origin
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.
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
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
Sprinkler v. manual suppression 30-90 seconds
after flames 13 GPM @ 10 PSI Very little has
burned Room of origin
still tenable to life Operates
automatically
8-15 minutes after report
200 GPM @ 100 PSI A lot has burned Entire home
untenable to life Someone needs to
call fire department
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 can’t
respond until someone calls
Fire can burn unnoticed until it breaks out of house
Why sprinklers? Builders build safe homes – then
people move in Houses don’t catch fire, contents do Contents loaded with synthetic
material Burn twice as hot, twice as fast
Homes are tight for energy
Why FD’s want sprinklers Can’t respond in time to save lives
Content fires go to flashover in 5 minutes or less
Occupants start dying halfway to flashover
Occupants who can’t get out under own power twice as likely to die The young, elderly
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
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
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
Sprinkler experience Zero lives lost in sprinklered homes
Scottsdale, AZ Napa, CA Prince George’s County, MD
Property damage (including water damage) nine times less
Fire departments handle with fewer stations and firefighters
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
NFPA 13 Area/Density curves
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.
Lower pressure = smaller area
Higher pressure = larger area
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
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.
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
NFPA 13D
Installation of Sprinkler Systems in One- and Two-Family Dwellings
and Manufactured Homes
NFPA 13D’s 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.
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.
13D objectives Limit maximum ceiling temp to
600°F. Limit temp at 5’ 3” to 200°F. 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.
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
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
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
Full scale tests Discharge rates Spray patterns Response sensitivity Design criteria Ability to maintain tenability to life
for escape time
Goal: Tenability in room of origin Carbon monoxide concentration
3000 PPM Temperature at breathing level
200°F Oxygen depletion
1980 edition Based on better understanding of
residential fires Had a new class of sprinkler Based on different method for
calculating minimum water flow
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
Sprinkler incentives Narrower streets Smaller setbacks Smaller water mains Fewer fire hydrants Fewer fire stations
WHAT LIES AHEAD
10-20 GPM v. 200 GPM
Fire threat, 1-2 family homes Sleeping occupants Small children, elderly and no
special exit arrangements Cooking facilities Smoking Unprotected vertical openings
House fires A low probability event, but a
high-consequence event A reasonably expected risk in this
community
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
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
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
Most victims in post-flashover fires are remote from the room of origin
Home fires by victim location& extent of flame damage
Flames
Victim Location Room of origin Beyond ROO
Intimate 7.3% 10.1%
In room - not intimate
6.1% 17.9%
Not in room 6.1% 51.5%
Unclassified 0.4% 0.6%
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
… characteristics.
Responds before room of origin becomes untenable to human life
Tenability: Eye-level temp > 150oF, moist air CO > 3000 ppm Smoke > .5 Optical Density/m
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
Residential fires 23 % of fires 80 % of fire deaths 75 % of fire injuries
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
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
Witness statements confirm model results Mother’s 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 firefighter’s description
Saw fire in kitchen as he started across street In seconds, flames were out front door
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