Quality, Consequences and the Construction Industrial Complex (part 140).
The RFI you should write on every project, IMHO.
Stairwell pressurization systems are a bit like software licenses, we all acknowledge and accept them without understanding or even knowing about them, then assume they work as designed. When was the last time a software license was rejected or a stairwell pressurization system rejected by the AHJ?
On many projects when the AHJ check stairwell pressurization system performance, they do a cursory witness and asks for a “stamped” report to cover their ass.
Why? Because the stairwell pressurization systems frequently do not achieve specified performance due to stairwell construction, fans and/or controls issues. However, as this testing is all done at project completion, it is a “tad” awkward when things do not go as planned, so everyone coughs and closes their eyes.
I am consulting on a nearly complete sky scraper in the Middle East and no-one is clear on the design standard and commissioning performance criteria for the stairwell pressurization system. Remember, the intention is that this system will operate on demand and save lives! This is a vital life safety and fire fighting system but there are fire fighters in many jurisdictions that have anecdotally, suggested they do not trust these systems. It blows my mind at construction professionals lack of understanding and ownership of them.
What to do if you are required to test and commission one of these systems? To obtain clarity and focus attention, I recommend every commissioning and TAB firm issue the following RFI as soon as they are appointed.
Prior to method statement / commissioning plan, functional performance test script submission, please confirm the following:
- Design standard adopted for stairwell pressurization systems e.g. BS EN 12101-6-2005, or NPFA 92 or?
- Ductwork leakage rate specified.
- Ductwork leakage testing standard specified e.g. BESA Sheet Metal Ductwork Air Leakage Testing DW/143 or HVAC Air Duct Leakage Test Manual ANSI/SMACNA 016-2012 or ?
- Testing & commissioning standard specified e.g. NFPA 3 or BS 5839-1:2013 Parts 1-8 or?.
- Number of “effective open doors” assumed in design and for testing & commissioning.
- Minimum and maximum differential pressure between closed stairwell door and adjacent area with all doors closed.
- Minimum and maximum differential pressure between closed stairwell door and adjacent area with fire / smoke event “effective doors’ open.
- Design air velocity through “effective open doors”.
- Design maximum door opening force to open stairwell door during a fire / smoke event.
Your ability to survive a fire / smoke event in a tall building rests on the efficacy of the design, construction, commissioning and maintenance of the stairwell pressurization system. Hell, it all really relies on a $250 pressure sensor and the maintenance teams ability to test and verify the system with stand-by power every six months.
My advice, if the fire alarm sounds, get out ASAP and try not to rely on the stairwell pressurization system!
My Stairwell Pressurization system cheat sheet is below for anyone interested.
Related posts & links:
#112 – Staricase Pressurization Systems – Who Wants It? ( https://bldwhisperer.com/staricase-pressurization-systems-who-wants-it/ )
#65 – Staircase Pressurization Systems – Life Safety with Single Points of Failure! ( https://bldwhisperer.com/staircase-pressurization-systems-life-safety-with-single-points-of-failure/ )
#40 GIT – The must do test that delivers working buildings ( https://bldwhisperer.com/git-the-must-do-test-that-delivers-working-buildings/ )