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Fire Alarm -- Description

The question is what kind of evacuation should be used -- Total Evacuation, Staged Evacuation, Defend in Place
In case of fire, Total Evacuation is where everyone leaves the building at once, Staged Evacuation is where those in the zone of the fire and adjacent zones leave the building first, Defend in Place is where everyone gets to a safe place in the building.
Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer






What is Total, Staged, and Defend-in-Place Evacuation?

By Douglas Krantz

For their own safety, when the fire alarm sounds, people want to get out of a burning building. Sometimes, though, there's a hitch in people's ability to evacuate; some buildings are easier to get out of than others:
  • Smaller buildings have easy escape routes
  • High rise buildings aren't easy because they don't have many escape routes
  • Hospitals, healthcare institutions, and prisons aren't easy because the residents can't just get up and leave
Each of these situations is different, and each requires its own specialized method of fire evacuation.

Total Evacuation -- Smaller Buildings

Fire! Get Out!
Total Evacuation -- Everyone immediately gets out of the building

Like a school, with Total Evacuation, if the alarms sound, they sound simultaneously everywhere. Everyone hears the fire horns or speakers, stops what they were doing, and withdraws from the building using fire exits.

In case of fire, smaller buildings are evacuated right away.

Staged Evacuation -- High-Rise Buildings

Fire! Let those in greatest danger escape first.
Staged Evacuation -- The phased withdrawal of the occupants

When there is a fire, if the escape routes are not large enough to handle everyone in a building at once, Staged Evacuation is the orderly withdrawal of people.

In Staged Evacuation, the alarm sounds near the fire. It's like shouting only to those in immediate danger, get out! The alarm sounds in the zone of incident (fire floor) and all adjacent zones (floor above and below).

For the rest of the occupants, there is either silence or an alert sound. It's telling everyone else in the building, those who aren't near the fire, "Stay where you are. Let those in danger get away, after that it's your turn."

Defend-in-Place -- Hospitals, Healthcare Institutions, and Prisons

Fire! Get to a place of safety inside the building.
Defend-in-Place -- Protecting those who can't leave the building

Hospitals, nursing homes, and even prisons present special problems because the people residing in there just can't just leave the building on their own.

In the case of hospitals, people often aren't able to get out themselves, or are put in danger by moving to what for others would be a safe place.

Residents in nursing homes are physically or mentally incapable of fending for themselves, and need assistance.

Prisons, of course, are a place where the residents aren't allowed to leave.

In a Defend-in-Place building, three different types of evacuation take place at the same time:
  1. Progressive -- Those in immediate danger get moved to a safe adjacent zone in the building
  2. Defense -- Those not in immediate danger are moved behind protective doors
  3. Evacuate -- Those who can leave, and are not needed to assist in the Progressive or Defense procedures, exit the building
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Fire Alarm Evacuation

Which method of evacuation people use -- Total Evacuation, Staged Evacuation, or Defend-in-Place -- depends on how easy it is for them to use the exits.

However, whether it's a Total getting out of the building that's on fire, a Staged withdrawal from the building, or Defend-in-Place inside the building, evacuation is still people protecting themselves from a fire.






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Describing How It Works
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Electrical Flow


On this website, most references to electrical flow are to the movement of electrons.

Here, electron movement is generally used because it is the electrons that are actually moving. To explain the effects of magnetic forces, the movement of electrons is best.

Conventional current flow, positive charges that appear to be moving in the circuit, will be specified when it is used. The positive electrical forces are not actually moving -- as the electrons are coming and going on an atom, the electrical forces are just loosing or gaining strength. The forces appear to be moving from one atom to the next, but the percieved movement is actually just a result of electron movement. This perceived movement is traveling at a consistent speed, usually around two-thirds the speed of light. To explain the effects of electrostatic forces, the movement of positive charges (conventional current) is best.

See the explanation on which way electricity flows at www.douglaskrantz.com/
ElecElectricalFlow.html
.