Stairwells are one of the most important passive features of buildings; they provide a mode of transport from one level’s built environment to the next, they can express a lot about the architectural character of the building, and in fact they are a key component of a building’s HVAC system. However, stairwells also have a critical role to play in emergencies of all types. This is why it’s so critical to ensure that the air quality within them is unassailable even under major disturbances, and why the proper pressurization of stairwells is so important. As HVAC specialist Abedelqader Hamdan puts it, “stairwell pressurization systems are designed to provide a smoke proof enclosure and a means of egress during a smoke control event.”¹ During a fire, smoke inhalation can be just as hazardous as direct contact with the flames. Preserving the air quality in this route of egress requires correct pressure differentials, tested based on locally-mandated protocols.

There are several ways to perform stairwell pressurization verification. These include testing with the exit door open or closed (local mandates will state the guidelines on this, but testing with the door open more closely approximates the real-life conditions that would be present during an emergency egress situation)¹. Stairwell pressurization is also not a single value; because air is compressible, the pressurization can vary throughout the entire stairwell. Guidelines will also recommend how at how many points these measurements should be taken, and sometimes they will even specify the location of those points. The door opening force can also vary, but a standard value is 13.6 kg¹. Due to the variety of parameters under which the stairwell pressurization verification can be performed, the deliverable report will include not only the results but a description of the test conditions if it’s not made clear in the local regulations.

Stairwell pressurization verification is based on a physical test of the location, so it is not built into the design verification phase of a construction project. Instead, it usually takes place right after the building has been constructed, and before it is opened for use at its zoned occupancy levels. Since stairwells are a key part of emergency egress from a building, it would be hazardous to perform these tests only after the building had been released into regular use. That being said, regular testing of stairwell pressurization, especially under circumstances where the building is incidentally empty or there is an alternative route of egress, is often recommended. Those considering this should check their local guidelines.

While air quality during smoke-related emergencies is one of the most critical functions of stairwell pressurization, a well-pressurized stairwell can provide benefits on a daily basis. Improper pressurization can lead to drafts, increased duct leakage, and overall energy losses by the HVAC system of the building. If the pressurization is at a dangerous level, the detriment to human health outcomes can be amplified by the fact that a stairwell is often a site of aerobic activity for the humans using it.

Stairwells are key to the safety of buildings and the optimization of HVAC systems. A stairwell pressurization verification can ensure that in the case of any emergency, this key exit route would function as intended.

-Nicole P