One means of keeping a stairwell free of smoke is to pressurize the stairwell.

• A. False
• B. Not applicable
• C. Only in high-rise
• D. True

Answer: (D)

Keeping a stairwell free of smoke is achieved by creating a positive pressure inside that enclosure. When the stairwell is pressurized, the air inside is at a higher pressure than the surrounding spaces, so when doors between the stair and adjacent areas are opened, air tends to flow out of the stair rather than smoke flowing in. This helps maintain a tenable, clearer path for occupants to evacuate and for responders to operate. The pressurization is usually provided by dedicated mechanical fans and dampers, designed to hold that pressure difference even as doors open and the fire evolves. Proper design and balance are essential; if not correctly set up, the system can fail to keep the stairwell clear or, in some cases, push smoke into other spaces. When implemented correctly, pressurized stairs are an effective way to keep egress routes usable during a fire.