The Truth About Elevator Shaft Pressurization

Elevator shaft pressurization is a code allowed option for elevator smoke protection. To the uninformed building designer, elevator shaft pressurization seems to be a simpler and less expensive solution than Smoke Guard or lobbies. However, the opposite is actually true. The reality is that making an elevator shaft pressurization system work is a very complex and difficult process. It is also difficult to price out and estimate the overall cost. Unfortunately, building owners think it is just some additional fans and ducting. So how expensive can that be?

R Occupancy Residential and I-1 Longterm Nursing Homes Do Not Allow Pressurization by Code.

The corridors in a residential occupancy or nursing home must be fire rated and smoke rated for all doors, including elevator doors. Pressurization is not an approved means of creating a smoke rated door, as stated in chapter 10. Chapter 10 calls for UL 1784 doors only. A Smoke Guard screen makes elevator doors, which do not pass UL-1784, pass. Therefore, Smoke Guard is generally accepted as a solution.

Pressure Range is Too Narrow For an ESP System to Work Reliably Year Round.

The graphic below shows the pressure curve in a 10 story building on a day when it’s 0 degrees (F) outdoors. In this case, the bottom floors are in negative pressure and the upper floors are in positive pressure (stack effect). This stack effect pressure is what would cause smoke from a first floor building fire to migrate quickly up the elevator shaft and spread throughout the top floors. If a fan was installed on the roof to create air pressure down the shaft, then at every gap in the elevators doors there is a significant chance that some floors would be over pressured. The building code specifies a pretty narrow range of allowable pressure, so that poses a problem. Additionally, as we all know outside temperature varies greatly from day to day and the stack effect can actually be reversed due to the negative pressure on the top floors and the positive pressure on the bottom floors during hot summer months. In this case a fire on the roof or top floor would suck the smoke down into the lower floors. Therefore, designing a mechanical system of fans ducts and dampers to work properly on any given day is very difficult and costly.

Stack Effect VS Elevator Shaft Pressurization

More About Shaft Pressurization

Shaft pressurization is allowed by code as an alternative to enclosed elevator lobbies, but there are many requirements to using this option. The chart below lists the elements required by the international building code to design and build an elevator shaft pressurization system, It also provides a way to cost out these key elements to obtain a clearer estimate of system costs if a dollar amount is estimated for each of line items listed.

View Checklist Full-Screen to Print It

Interested in learning more about designing an elevator shaft pressurization system that meets the IBC requirements?

Try this link. It goes to the most current Society for Fire Protection Engineers article published by Dr. Rich Miller at Clemson University on elevator shaft pressurization and outlines some of the pitfalls in designing a properly functioning system.

By taking the time to review the Findings section and section on “Possible Solutions” in Dr. Miller’s article as well as reviewing the checklist you will be better versed on what designing a shaft pressurization entails.

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