Staircase not fully pressurised to final exit

[Messy]

I have come across a building with multiple staircases, all but two of them are fully pressurized.

The other two staircases are pressurized from basement level 4 to just below the ground floor. The remaining floors 14 floors have no auto ventilation, or natural ventilation, other than an openable window one floor down from the top.

I am unhappy about this, as the MOE from the sub surface levels is protected by pressurization to one flight of stairs below the ground, where there's a door across the stairs. From there to the final exit its unpressurized and unventilated.

They are not firefighting staircases (so this is not about ensuring firefighter access), but surely if the MOE is protected by pressurization, it should (like a traditional protected route) extend to the final exit??

Any views??

[nearlythere]

I have come across a building with multiple staircases, all but two of them are fully pressurized.

The other two staircases are pressurized from basement level 4 to just below the ground floor. The remaining floors 14 floors have no auto ventilation, or natural ventilation, other than an openable window one floor down from the top.

I am unhappy about this, as the MOE from the sub surface levels is protected by pressurization to one flight of stairs below the ground, where there's a door across the stairs. From there to the final exit its unpressurized and unventilated.

They are not firefighting staircases (so this is not about ensuring firefighter access), but surely if the MOE is protected by pressurization, it should (like a traditional protected route) extend to the final exit??

Any views??

Why are they pressurised Messy?

[Phoenix]

I cannot see a problem with this set up from what you describe.  What problem do you see?  Are the un-pressurised stairs not lobbied?

[Messy]

The staircases are lobbied except for the ground floor

They are pressurised to allow for slightly longer travel distances to the staircore on each floor than ADB allows.

Obviously, if a MOE is protected, it should be all the way to the final exit without any gaps. However, the MOE is only part pressurised.

This is a very large and complex building and I think my head was full to bursting at the end of the third day of my FRA walk-round!!! Now I have had time to get my head around it and I am no longer so anxious

Thanks for your assistance

[wee brian]

Generally this is frowned upon. As I recall there is a concern that the pressurised stairs will pussh smoke into the unpressurised ones.

Not sure how any of this helps with extended travel distances but hey!

[Phoenix]

There is no risk of smoke entering the unpressurised parts of the staircases due to their immediate adjacency to the pressurised parts.  However, there could be a risk of smoke entering the unpressurised stairs due to the other remote pressurised staircases.  The designers will have had to deal with this and there should be outlets for the pressure at appropriate locations on each floor between the staircases.  Probably by means of a small number of AOVs around the envelope of the building.

[wee brian]

sounds dodgy to me but I'm a few years out of date on these systems