Smoke Control Systems Voluntarily Provided?

MeyerFire University | SM001.03

By David Stacy, PE

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TRANSCRIPT

When are Smoke Control Systems Voluntarily Provided? 

INTRODUCTION

In our last segment we talked about where smoke control systems are required. There are several triggers for required smoke control systems, like Atriums and Windowless Buildings. 

But we also alluded to the concept of voluntarily providing smoke control systems. There are many instances where a smoke control system is not required, but it is a code alternative that is often used because these systems can provide an equivalent or higher level of life safety with a less expensive overall building design. 

Let’s explore that concept in detail today. 

VOLUNTARY APPLICATIONS

We can’t be all-inclusive and list every application that smoke control systems are used, because they can be used as a code alternative in any variety of situations. 

Some of the most common ones, though, include:

• Stair Pressurization
• Elevator Pressurization
• Smoke Protected Seating
• Alternative Means & Methods

Let’s start with Stair and Elevator Pressurization. 

STAIR AND ELEVATOR PRESSURIZATION

Stair Pressurization is one code alternative that’s used all the time. It’s an alternative to ventilated vestibules or exit stairwells that are open to the exterior. 

What is Stair Pressurization?

We’ll spend plenty of time on this in the future, but it’s an approach to keep the volume of air inside a protected stairwell at a higher pressure than the surrounding spaces. This positive pressure prevents smoke and its hot and toxic byproducts from entering a stairwell through openings, penetrations, or leaks or cracks in the stair.

Why use Stair Pressurization? 

These are often used because they save floor space, which is valuable and expensive, and it’s also often easier to provide than the other options.  

Where does Stair Pressurization show up in code? 

The IBC actually lists Stair Pressurization as one of the alternative methods.

What about elevator pressurization? 

The same concept applies as stair pressurization.

SMOKE PROTECTED SEATING

Another common application is for smoke protected seating. 

The concept for smoke control within a large assembly space, like say an arena, is that if we can prevent smoke from descending down into the occupiable seating areas, then we’re affording occupants more time to evacuate.  

When we afford occupants more time, then we don’t need egress to be quite as wide and quite as conservative. 

The IBC spells this out for us when we’re calculating the capacity of the means of egress. It shows up in Table.  

For very large arenas, we can sometimes show that there’s enough volume at the top where smoke can simply collect naturally and fill that volume without harming occupants. In that case, we would do “smoke fill” calculations to simulate different fire scenarios and show how tenability is maintained for occupants until they’re able to egress even when smoke is filling a “smoke reservoir” above. 

For smaller or mid-size arenas, like your smaller collegiate stadiums, this would be very difficult to achieve. These arenas often have lower ceiling heights and not a lot of extra volume at the top where smoke can bank.  

Even in very large arenas, though, our design fire can get very large, like a 10 MW if not larger fire. What if there are to be car shows, and a potential fuel load is a large size vehicle or multiple vehicles in a show on the arena floor? That could cause a smoke layer to collect and descend very quickly, so we may need an active smoke control system to exhaust the smoke, bring in makeup air, and keep the space tenable for a longer period of time.  

ALTERNATIVE MEANS & METHODS

What we haven’t discussed yet is alternative means and methods. What if we have an existing building that has too far of a travel distance to exits?  

What if an existing building is increasing its occupant load, and the egress falls short in size or number? 

What if new tenants come in with new needs? 

A lot of times with existing buildings, and especially historic buildings, we can be very limited in what we’re able to change.  

In some cases, we can leverage use of a smoke control system as an additional level of safety to allow more time for occupants to safely egress and overcome a prescribed code issue. These can be great opportunities to improve life safety in a tangible way. 

SUMMARY

So here in this segment we introduced a few applications for smoke control systems that are not mandated by code, but are often used in the real world.  

These “voluntary” systems commonly include stairwell pressurization, elevator pressurization, systems for smoke protected seating, and systems provided as an Alternative Means & Methods to overcome code challenges elsewhere.  

In our next segment, we’re going to dive into what Codes & Standards apply to smoke control systems.

I’m Dave Stacy, this is MeyerFire University.