Yale University Mist Fire Control System Presentation

Choose one of the following fire scenarios for initial consideration of a special fire

‏protection system from the following: clean agent, CO2, water mist, firefighting

‏foams. You may ‏use the performance-based fire protection analysis flow chart in your presentation.

‏No matter what fire protection system you selected, the following

‏items/components of your design should be mentioned. Note that cost is not the

‏biggest concern in your design, but all your designing should make sense.

‏1. Type of system

‏2. Working principles

‏3. System advantages and limitations

‏4. System major components

‏5. Alarm system and notification/warning requirements

‏6. Potential fire types and size (HRR)

‏7. Evacuation requirements

‏8. Nozzle selections

‏9. Design Quantity and design concentration/pressure

‏10.Discharge flow rate and time

‏Scenario 4.

‏A mid-size hotel in rural area where water supply is constrained (Water Mist).

Extinguishment with water mist
Definition
What is water mist?
A water spray for which the Volume Median Diameter (VMD) Dv0.99,
for the flow weighted cumulative volumetric distribution of water
droplets, is less than 1000 micron ( 1mm) within the nozzle operating
pressure range.
Dv0.99: 99% of water volume is in drops with diameter less or equal to
this value
Droplet size
https://www.orrprotection.com/
Regulations
MECHANISM OF EXTINGUISHMENT
REMOVES HEAT: The mist droplets evaporate and remove heat either at the surface or within
the flame. The mist can also block radiative heat transfer between fire and combustible.
• Wetting and cooling of the fuel surface;
• OXYGEN EXCLUSION: Fine droplets evaporate before reaching flame, generating steam that
dilutes the oxygen percentage.
• The induced gas current helps overall cooling and dilution and can blow out flame.
• Kinetic effects
LIKE OTHER AGENTS, PERFORMS THESE SIMULTANEOUSLY
Objective
Protect lives and property
Control room temperature to prevent flashover and
fire spread
Extinguish class A and class B fires
Use water where Halon or CO2 were previously used
Provide freedom from sprinkler system design
constraints ( smaller pipe size) with equivalent level of
safety
ADVANTAGES OF WATER MIST
LESS WATER = LESS DAMAGE
Reservoir options
Nitrogen driven options for remote locations
Reduced infrastructure (lower cost)
Reduced likelihood to existing building water supply
system upgrade
Fast acting
Three dimensional
Etc.
Explosion Hazard Mitigation
with Water Mist
Explosion Hazard Mitigation
with Water Mist
DISADVANTAGES OF WATER MIST
MOMENTUM &
DIRECTION
DROPLET SIZE
CONSIDERATIONS
INCIPIENT
STAGES
Applications
Machinery spaces
Turbine enclosure
Marine accommodations
Hotels, heritage buildings
Electrical equipment rooms
Ideal for
very large spaces
Hot class B spay fire
Light hazards
Remote locations such as wind turbines
NFPA vs FM approval
Videos
https://youtu.be/C1r5xovZr‐E
https://youtu.be/kq8N‐9TaoZc


Summary
Water mist system technology has become a global fire protection market in the
second decade of the twenty‐first century.
Especially in Marine sector, where water mist was competitive with marine
sprinkler systems on passenger ships.
Highway and rail tunnel fires.