Fire Protection: The Whole Story May Surprise You

by Mike Lehner, P.E.

This article is part of Wood Harbinger’s newsletter series.

When you think about fire protection, what comes to mind? Fire hydrants? Fire sprinklers? Every sprinkler head in the building going off in some Hollywood movie? In reality, each sprinkler head activates in its own sweet time, when the temperature in the area reaches a certain threshold. That reduces excessive sprinkler flow and assures the system operates correctly.

But is fire protection just sprinklers? Not at all! While sprinklers go a long way to help, building construction, exits, fire alarm systems, and other fire suppression systems also come into play. Fire protection engineering and consulting expertise is required in many aspects of building design and construction, and requires multidiscipline coordination and considerations.

So what is fire protection all about?

Fire protection is about protecting lives and property, in that order. The life safety aspect of fire protection includes alert systems, egress (exit) systems, and building construction features. People need to be alerted when there is a fire. They also need to have multiple ways to get out of the burning building. Building construction can also include elements that can slow down the fire, which buys time for people to escape. Let’s take a closer look at the considerations for each of these aspects.

Fire Alarm/Alert Systems

How do you know there is a fire in the first place? Enter the fire detection and alarm systems. These systems detect when a fire is present and sound an alarm throughout the building to tell occupants that there is a fire. Fire protection engineers coordinate with electrical engineers, A/V and electronic system engineers, plumbing engineers, and architects for these types of systems.

Many buildings use the fire sprinklers to detect the fire (using a flow switch), while other fire alarm systems may have smoke detection. Other types of detection include laser beam detectors (where smoke breaks the beam), flame detectors (in effect “see” the fire), and heat detectors (activate when heated up). Air sampling systems are also provided in some situations, which can “sniff” out the smallest amount of smoke to give users more time to stop the fire before it starts.

The fire alarm system notifies people using sound and visual signals, usually horns and strobe lights. The fire alarm system is triggered by the fire detection system or by using a pull station (the red fire alarm near an exit door). You may have noticed Hollywood also makes use of fire alarm pull stations when characters need to create a distraction!

A mass notification system may also be provided in high-occupancy buildings. Mass notification systems include speakers instead of horns to alert large amounts of people in specific areas in the building. The speakers can relay pre-programmed messages and instructions to building occupants. To assure intelligibility, speakers are spaced more frequently throughout the building.

Egress Systems

The key to egress (exit) is being able to get people out of a building quickly with the least amount of confusion and danger. Egress systems provide a safe path to help make this happen. Fire protection engineers coordinate with architects, electrical engineers, and structural engineers to assure that the building supports a safe and speedy exit in an emergency situation.

The size and number of exits depends on how many people are in the building, the size and height of the building, and how the building is used. Exits must be large enough and plentiful enough to accommodate the volume of people in the building and allow for a quick exit. For example, a conference hall’s exits will be different than those required for a warehouse; this makes sense because a conference hall, by design, holds more people so it needs more exits.

Exit stairs are separated from the building interior so that the route remains safe from smoke and heat. This includes a firewall “wrapping” around the stairwell to keep smoke, fire, and heat out so that people can escape from the building unharmed. Exits must also be clearly marked with lights and signage so people can quickly find their way out. These devices are equipped with battery backup so that they will light the way to the exit even in the event of a power outage.

Building Construction for Fire Protection

Acceptable construction materials are prescribed by the building code and include a range of choices from Concrete Type I to Wood Type V. These types are ranked according to their combustibility:

• Type I includes concrete and other fire resistant materials that are non-combustible and have a higher heat retention, which slows fire movement, providing the best protection;
• Type II includes more types of non-combustible materials, with reduced heat retention;
• Type III includes Type II, but the building roof can be made of combustible materials;
• Type IV includes buildings with heavy timber construction (thick wood beams);
• Type V includes combustible materials (wood).

The building code is written to preclude large buildings from being made of wood or other combustible materials. For instance, high rise buildings are always Type I because of their dense occupancy and egress accessibility. Type I construction helps assure that (in the event of a fire) building occupants will have time to get safely out of the building before it is structurally compromised.

Standpipe Systems

Have you seen the hose valves in the stair wells, or hose racks in a corridor? That is the standpipe system. The standpipe system allows the fire department to quickly get fire hoses in place in remote areas of the building to attack the fire. Without standpipes, the fire department could be delayed in putting out the fire in a building.

Standpipes have an inlet connection outside of the building that the fire department charges up with their fire trucks. The system extends into the building and usually includes 2.5-inch hose valves to allow the fire department to connect their hoses much closer to where the fire actually is. Standpipe systems come in many types, ranging from a manual-dry system to a fully automatic-wet system that is ready for fire department use.

• A manual-dry standpipe system is used in parking garages, where there is potential for freezing at times. It is a normally an empty pipe, which only works when the fire department is charging the line.
• A manual-wet system is used in low-rise buildings that need standpipes. It is always filled with water, but this water source doesn’t provide enough flow; the fire department must still charge the line as well.
• A Class II standpipe is used in some older buildings. These systems have 1.5-inch hose valves that are intended for use by building occupants to fight the fire. However, it is fairly common for fire departments to require that occupants flee the building and let the fire fighters do the work of conquering the fire.
• Automatic-wet standpipes are used in high-rise buildings. At all times, these systems provide the high pressure (usually at least 175 psig) required for fire department use. A fire pump is on standby to provide the high pressure and includes a water storage tank for redundancy.

As you can see, there’s far more to building fire protection systems than just sprinklers! Buildings codes require different elements for different buildings, and these systems work together to provide superior fire protection for life safety and property protection. These critical systems are a key component of safe and effective buildings. While you’ll probably keep seeing movies with all the sprinklers going off, now you’ll know to look for the exit signs, strobe lights, standpipes, and stairwells that are an integral part of the full fire protection system.