Quiz 13

Question 1

Why is visibility an important parameter during evacuation in a fire scenario?

Answer 1

o Statistics suggest that 90% of survivors travel less than 16m through smoke
▪ Exposure to toxic combustion productions is the prime hazard
o Maximise safety must minimise exposure
o Exposure time depends upon visibility
▪ Direction of travel
▪ Speed of movement
o Enhance visibility should increase safety

Question 2

What is the current status of modelling visibility?

Answer 2

o Typically empirically based
▪ Homogenous smoke zones
▪ Steady state
▪ Specific configurations
o Do not account for
▪ Secondary illumination
▪ Light scattering
▪ Spatial variation of smoke
▪ Transient effects
▪ Complex geometry

Question 3

What is the difference, if any, between radiation and light attenuation (and in the extension visibility)?

Answer 3

Not much more than wavelength of interest

Question 4

How would you define visibility?

Answer 4

Define visibility as the distance at which an object can just be identified

Question 5

Which colour (wavelength) gets extinct the fastest by smoke?

Answer 5

Blue (shorter wavelength)

Question 6

What is the difference between so called black and white smoke?

Answer 6

o White smoke scatters

o Black smoke absorbs

Question 7

Do you see any weaknesses in the way that light-reflecting signs are treated in FDS (and in general)?

Answer 7

Light has to come from somewhere, how do you know the amount that actually hits a surface?