Hazard Analysis
EXAMPLE HAZARD ANALYSIS
At =
=
fractional effective dose at the end of interval i (dimensionless);
concentration of material burned at interval
time interval,
lethal exposure dose from test data, (g min). materials that started as fuel that have accumulated at a location during the interval i. The concentration has units of mass of the material burned per unit
The lethal exposure dose, is the product of the and the exposure time. The is the concentra- tion of airborne products that is lethal to 50% of the subjects exposed for a specified time. An FED of can be considered a rough indication of inca- pacitation.
When a accurate evaluation of effects is desired, the methods discussed in Chapter can be used.
The fractional incapacitating dose method is gen- erally considered to be more accurate. Unlike the FED method. calculation of calculation of spe- cies concentration. The considcsed can be
to and CO. This allows simulation of the synergistic effects CO production and depletion on toxicity of CO. Considering this and that the CO the dominant toxic gas in building fires, limiting the gases to and CO is appropriate for many applications. For information about CO production in fires, see Table
For any instant, the visibility can be calculated from
where
= visibility at the end of interval i, (m);
K = proportionality constant (8 for illuminated signs, and 2 for non-illuminated signs);
= mass optical density,
= concentration ofmaterial burned in interval i,
Generally, contact with dry air of temperatures greater than 250°F 2 1°C) can be expected to result in skin Also, contact with dry air at a
less than approximately 250°F (121°C) leads to For hyperthermia, heat exposure can be esti- mated
where
= total cumulative dose (dimensionless);
At = time interval, minutes;
If contact with gases does 'not in
tion due to thermal radiation from those not result in incapacitation for the same exposure time. Generally, exposure to thermal radiation
is not- For situations
where radiation is significant, see Chapter 3.
EXAMPLE HAZARD ANALYSIS
Hazard analysis has a wide range of applications, and this was selected to illustrate some of the capabilities and limitations of this technology. The is a six-story hotel (Figure 9.1) with a lire in one the guest rooms on the ground Both
Chapter 9- Hazard Analysis
VEND HK
R01 R02 R03 R04 R05 R06 R07 R08 R09 R10
STG .. ELEV
(b) Plan for Floors 2
-
6 Note: Floor 7 has mechanical penthouse (not shown).. . . .
R01 R02 R03 R04 R05 OFF , R07 R08 R09 R10
ELEV (a) Ground Floor Plan
Rn Room STG Stoiage Room HK House Keeping
COR Corridor OFF VEND Vending
ELEV Elevator C
-
WindowW Office Window Door
t
Table 9.1 :
Roughly S t e a d y Temperatures for First Floor R o o m s of Hotel Fire Example Based o n FAST Simulation Temperature
Location
Fire 1700 927
Corridor Section Open to Fire Room COR l 470 243
Corridor Section to the COR 280 138
West Section of Corridor 82
location
window and door of the fire room are opened. open window is large enough to allow combustion air to sup- port a fully developed 5 MW fire (Chapter ?).
CONTAM was used for the smoke transport analy- sis. The temperature of most of the building locations is 73°F and the outside temperature is (-
CONTAM does not include equations, the temperature of the tire room and that of the other spaces open to the burn needs to bc
The flow areas used i n the CONTAM simulation are listed in Table For this simulation, the integrity of the door is considered to be maintained, and warping of the door is considered. When subjected to elevated temperatures, some doors experience at edges or may warp to increase the area of the gaps around door edges. doors are sus- ceptible to burn-through, and warping is more pro- nounced with steel doors.
FAST was used to calculate these for the tenability calculations are
(Table 9 . l). listed in Table 9.3. The valuesof K, and are
Principles of Smoke Management
Table 9.2:
Building Flow Used for Hazard Analysis of Hotel Fire Example
Flow Path Path Name
Equivalent Areas of Shafts:
Elevator Shaft FLOOR-EL 770
Stairwells FLOOR-SW 32 3.0
I . Flow areas arc for a loose or relatively leaky building. and for further areas. see Chapter 6. Flow coefficient, C. o f was used for all paths except Tor the open door, which 0.35.
2. These leakage paths are uniformly over the height door or window.
Table 9.3:
Parameters Used for Hazard Analysis of Hotel Fire Example
Steady heat release rate, 5000 (4220 kW)
Chemical heat of 10,700 (25,000
Proportionality constant, K 8 (for illuminated signs)
Mass optical density, 1600 (0.33
Lethal exposure dose for a developed fire, g
Exposure 30 minutes
for most applications, and the value o f
applicable for fully developed fires. For appropriate parameters for other fires, see Chapter 3. An
time o f minutes was used for this example. For a spe- cific application, the exposure time would depend on a number of factors. If this were a failure analysis for a design study, evacuation time be taken as 15 to 30 including the time before people moving.
For a fire reconstruction, the exposure time might be taken from the estimates o f the people movement based on the fire event time line developed as part of the fire investigation.
The tenability calculations did not explicitly include heat exposure. Because the temperatures in this are the of temperature can be obtained from Figure 3.7. A person could withstand an
exposure to 180°F (82°C) for about minutes, and a person could withstand exposure to 280°F (138°C) for about 4 minutes, after which they would suffer skin bums. Tolerance to higher temperatures would be much less. From this, it can be seen that the probability o f fatality due to heat exposure is high for many spaces on the first floor during this fire.
The results o f the tenability calculations are listed in Table Graphic presentation o f tenability results can be useful. The results o f the toxicity calculations are shown graphically in Figure and it can be seen that the FED exceeds one for many spaces on the first floor.
For these spaces; the probability of fatality is very high.
The visibility is shown in Figure 9.3, and i t can be seen that the visibility is less than 25 ft (7.6 m) throughout the ground floor. On all floors, visibility in the stairs is less than 25 ft (7.6 m).
Chapter 9 Analysis
Table 9.4:
Summary of Tenability Calculations for Hotel Example
Time (minutes) to Visibility of FED for 30 min
Summary of Tenability Calculations for Hotel Fire
Time (minutes) to Visibility of FED for 30 min
Principles of Smoke Managemerit
3rd - 6th Floors
STG
Cross hatching indicates FED between 0.5 and 1 .O.
2nd Floor
Ground Floor Shading indicates FED of 1.0 or more
Figure 9.2 Toxicity for- exposure of ho fire