Smoke exhaust – it’s serious
impact of the CO management which should be undertaken
by the smoke ventilation specialist creates a high level of
extraction with zero chance of diversification of the CO
extraction rate. As an example, a three level basement
requires double the extraction rate for CO versus the smoke
extraction requirements. A 10 level basement (which is not
uncommon in complex multi-level occupation buildings)
requires six times the extraction rate for CO as opposed to
the smoke ventilation requirement.
The challenges of the stair pressurisation system remain and
are only marginally more complex due to the duct requirement.
It is important not to let the air into the stair at too high a
velocity or noise level as this is going to prevent the people
from entering the staircase. Most people do not understand the
dynamics of the pressurisation systems and will not enter due
to fear created by excess noise levels.
Naturally the lift lobbies carry the same concerns as in the
simple building. It’s a little more challenging in a multi-level
basement as this creates a challenge with pressurisation
and fire fighter access to a level below the fire to attack and
extinguish the fire at its seat.A complex hotel is built to make
a statement. The external façàde is one aspect, however the
internal ambience of the space is where the designers take their
licence to a special level. Multi-level atria are mainly the rule as
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opposed to the exception. Smoke channelling, is a requirement:
open access and large spaces require astute planning when
considering the smoke ventilation pathways.
When dealing with the atria it is important to prevent smoke
bleeding into the atria, as this converts the atria into internal
chimneys. The architect will have spent significant effort and
resources ensuring the sight lines are not obstructed. This space
needs to convey a specific feeling of uninhibited freedom,
which cannot be achieved with glass, steel or concrete.
There will be a requirement for the installation of
automatically operated fire curtains isolating the atria from
the fire floors. The option of using the now enclosed atria as a
smoke duct significantly reduces the requirement of multi--
ducted smoke extraction systems, however there is a financial
cost associated with the use of high level engineering.
Budgeting a project of this nature is a fluid exercise that
requires the combination of various skills, as each option comes
complete with its own unique set of challenges which, although
conquerable, require astute application of code requirements.
Caution rather than valour is paramount when approaching a
hotel building which can, over the holiday periods, contain a
high occupancy, who often are revelling in a party mode, paying
little attention to escape routes. Ensuring their safety in the
event of a fire is paramount. RACA
RACA Journal I June 2019
73