Life safety has three goals:
- Protection of life
- Protection of property
- Restoration and use of the building after a fire
While fire is the primary focus, life safety also encompasses other emergencies such as earthquakes, floods, blackouts and terrorism.
Compartmentalization is a key concept within life safety. Its aim is to contain a fire, limit its spread with the dual objective to allow occupants to escape the building and protect the unaffected parts of the building.
Compartmentalization is achieved structurally through:
- Door ratings
- Floor-ceiling assemblies
- Fire-rated walls
- Fire separations
As a designer, you need to know the different types of devices and appropriate locations within based on code requirements. Life safety equipment includes the following:
- Exit signs – ceiling-mounted, door-mounted
- Emergency lighting
- Audible/visible fire alarms
- Fire extinguishers
- Smoke detectors
- Sprinkler systems
A fire partition is a wall with a fire-resistance rating of 1-hour. Most common fire partitions are used in the following locations:
- Corridor walls
- Elevator lobby (high-rise buildings and I-2, I-3 occupancies)
- Walls separating dwelling units (apartment, dorms, etc.)
- Walls separating guests rooms in residential (R-1, R-2) and I-1 institutional occupancies
- Walls separating tenants in covered shopping malls
A fire barrier is vertical or horizontal structure that is fire-resistance rated and specially designed to confine fire and allow for safe passage.
A fire barrier offers a higher level of protection than the fire partition because it is continuous from the floor slab to the underside of the floor or roof above.
Fire barriers are used to:
- Enclose stairways, exit passageways, horizontal exits and incidental use areas
- Separate different occupancies in mixed-use occupancies (unless specified otherwise by code)
- Separate single occupancies into different fire areas
Egress is synonymous with exiting. You'll often see the term “means of egress” too.
Egress needs to be continuous, unobstructed and possible from any point in the building. Egress leads to a public way, which is a public area outside that is a minimum of 10 feet wide. Some examples include a street, alleyway or park.
Egress has three parts:
- Exit access – the portion that leads to the exit. Exit access can include aisles, corridors, hallways and intermediate rooms, among others. Exit access may or may not be fire-protected, but the important thing to remember is that the length of the exit access is measured and regulated.
- Exit – the portion that provides a protected path between the exit access and the discharge. Exits must be fully enclosed and made of fire-resistive construction (walls, doors, windows). Exits are either 1-hour or 2-hour rated, depending on the building specifics.
- Exit discharge – the portion between the exit and the public way. While they are usually outside, common exit discharges include balconies and exterior stairways. Some building lobbies qualify as exit discharge areas, with some conditions.
Common path of egress travel
The common path of egress travel is the part of the exit access that is taken before two separate paths to two different exits becomes available. It's like a fork in the road. The common path of egress travel distance is based on the occupancy type.
Most occupancies have a maximum common path of egress travel distance of 75 feet. Some occupancies increase that distance to 100 feet if the building is sprinklered. Assembly and hazardous occupancies do differ from the norm, so be sure to check the code requirement.
Another factor to keep in mind is that all paths of egress must meet accessibility codes. Be sure to review these.
Number of exits required and arrangement
The number of exits required is largely based on the occupancy type, the occupancy load of the space itself, and limitations on the travel distance length. Every building must have at least one exit.
On the NCIDQ Exam, you are provided with an occupancy load table to determine the number of exits required.
When two exits are required, they must be located at a distance not less than 1/2 the length of diagonal dimension of the room. In other words, if the room diagonal measures 100 feet, the two exit doors must not be less than 50 feet apart from each other. (If the building is sprinklered, the distance is reduced to 1/3). It basically prevents two exit doors from being close together while apart from the rest of the room.
Maximum travel distance
Also known as travel distance, it's the distance an occupant must travel from the most remote point of the exit access to the nearest exit. Again, the distance is based on occupancy type and whether the building is sprinklered.
Width of exits
Minimum exit width dimensions are figured by multiplying the occupant load by the figures below. Note that the dimension calculated cannot be less than minimum widths specified elsewhere in the code, like the 44-inch minimum corridor width.
- 0.3 per occupant in stairways
- 0.2 per occupant in other egress components, like corridors
If there two or or more exits are required, the total width must be divided so that if one exit becomes unusable, the capacity of the other exit is not reduced by more than 50% the overall required capacity.
On the NCIDQ Exam, you are provided with a minimum exit width of 40″ in the NCIDQ Building Codes.