To fire/smoke damper or not to fire/smoke damper ... that is the question

[Revol]

Just wanted to canvas opinion on the interpretation of 33.4.5.1 of BS 9999 which if read in isolation effectively states that fire/smoke dampers, operated by a suitable automatic fire detection system need not be installed in cii and ciii (sleeping risk but not long term tenancy) if there is L1 AFD coverage and an immediate (note not simultaneous) evacuation strategy. 

It's interesting that the 2016 Draft of BS 9999 has now added additional guidance (clause 32.5.2.3 and 32.5.2.4) that very clearly advises against the use of fire dampers only in C characteristics.   

[Phoenix]

This is how I see it.

You need dampers (or other equivalent methods as outlined in the guidance) where ducts pass through compartment walls.  These can either be actuated by heat (fusible links, intumescence, etc) or by smoke. If actuated by heat then they do not perform well to protect occupants who may not be in a position to evacuate the building quickly. 

33.4.5.1 states that hotels and boarding houses, etc, need dampers operated by smoke detection which makes good sense.  But it then gives a concession and I think it has a typo.  It states that if there is an L1 system and everyone can evacuate immediately and unaided then no dampers are needed at all!  I think it is meant to say that dampers actuated by smoke detection are not needed (i.e. intumescent or fusible link dampers are acceptable).

In the second paragraph a) (why does it have two!?) I think that where it states, "then fire/smoke dampers are not needed", it should state, "then smoke detector operated fire/smoke dampers are not needed".

[Phoenix]

Incidentally, I don't like the concession of allowing heat operated dampers where people are sleeping.  Sailing a bit close to the wind in my mind.

[Jim Scott]

This is how I see it.

You need dampers (or other equivalent methods as outlined in the guidance) where ducts pass through compartment walls.  These can either be actuated by heat (fusible links, intumescence, etc) or by smoke. If actuated by heat then they do not perform well to protect occupants who may not be in a position to evacuate the building quickly.  

33.4.5.1 states that hotels and boarding houses, etc, need dampers operated by smoke detection which makes good sense.  But it then gives a concession and I think it has a typo.  It states that if there is an L1 system and everyone can evacuate immediately and unaided then no dampers are needed at all!  I think it is meant to say that dampers actuated by smoke detection are not needed (i.e. intumescent or fusible link dampers are acceptable).

In the second paragraph a) (why does it have two!?) I think that where it states, "then fire/smoke dampers are not needed", it should state, "then smoke detector operated fire/smoke dampers are not needed".

That's exactly what 10.13 in ADB says Phoenix.

ADB only requires dampers in the situation you cite, for phased evac.

Bear in mind though, this only covers compartmentation, not FR required for means of escape.  This is further clarified by 5.48.

It looks like BS 9999 is virtually identical in its requirements.

[Revol]

Thanks for the reply chaps. I have a current proposal with plastic ventilation ducting passing from the bedrooms into the protected escape area with intumescent wraps. Not giving me warm fuzzy feelings!

[Jim Scott]

That's a very different position, as the means of escape would not be protected.

Yes we could negate the dampers passing through compartment floors and walls, although the fire resistance must be maintained to the escape routes.

That leaves you with the classic three methods of FR boxing, FR ducting or electricity operates dampers at the line of fire resistance. Have a read of ADB 5.48 for clarity.

I am involved in a lot of hotel builds and often get asked questions about bedroom ducting.

[col10]

Plus sound insulation to consider, which placcy ducting on it's own wont suffice without boxing in.

[Revol]

That's a very different position, as the means of escape would not be protected.

Yes we could negate the dampers passing through compartment floors and walls, although the fire resistance must be maintained to the escape routes.

That leaves you with the classic three methods of FR boxing, FR ducting or electricity operates dampers at the line of fire resistance. Have a read of ADB 5.48 for clarity.

I am involved in a lot of hotel builds and often get asked questions about bedroom ducting.

I agree this is a completely different situation ... the current guidance seems to imply that the exception to above is if there is L1 and immediate evac, in this case a fusible link fire damper is acceptable. Clearly the 2016 BS 9999 guidance seeks to add some clarity on this. Interestingly the fire engineers view is that its fine to have some smoke in the corridor as it will be above the ceiling. 

[Jim Scott]

Interestingly the fire engineers view is that its fine to have some smoke in the corridor as it will be above the ceiling. 

Really? Where did you get that from?