Air Conditioning Plant on External Escape Routes.

[Bill J]

Hi Guys.

More and More Often I am finding Air Conditioning Plant, Cooling Fans, etc, On External Escape routes, including at various levels on metal external escape stairs.

Is this permissable by building control?

I heard one contractor state that as its external, they could use the main staircase if the Plant were on fire, but would not accept that people who had just come down 5 flights, were not going to be able to walk back up 5 flights.

Is it possible to enclose this kit in FR materials, or does it need to be in the open air?

Where is the chapter and Verse on this?

Thanks in advance

Bill

[Chris Houston]

The part of the "Split" air conditioning units that you undoubtedly see do need to be situated externally, within a certain distance of the other part of the unit.  That's not to say I am saying they should be on escape stairs, I'll leave that part of the question to someone else.

[Ricardo]

Bill

Under the Building Scotland Regs 2004, technical handbook for non domestic,  an external escape stairway should be protected against fire from within a building in accordance with the following, (however, fire protection need not be provided to an external escape stair with a total rise not more than 1.6 metres)

Every part of an external wall(including a door, window or other opening)not more that 2metres from the escape stair,should have short fire resistance duration.However this does not apply to a door opening from the top storey to the external escape stair. Fire protection below an escape stair should be extended to the lowest ground level.

Due to the likely smoke dissipation to atmosphere, service openings including ventilation ducts not more than 2metres from the escape stair may be protected by heat activated sealing devices or systems.
Hope this is of some value to you.

[wee brian]

I doubt a heat activated device would be any use. Smoke can be quite cool by the time its got to the roof.

Some AC Plant will not actually have a duct connecting with the building. This is most liekly the case for the things you find bolted to the external stairs.

They could catch fire but as they are bolted to a steel stair there is very little risk of the fire spreading. So there will be no need to evacuate the building.

In short, I wouldnt worry about it.

[Bill J]

Thanks Guys.

Words of wisdom (and good old fashioned common sense) as always.

Bill

[Firewolf]

Hi Bill

I'm an ex Air Conditioning and ventilation engineer.

Split air conditioning systems comprise of an indoor ceiling or wall mounted air conditioning unit connected via refrigerant pipework and electrics to an externally mounted condensing unit.

The condensing units can not readily be enclosed in an FR construction as they need to draw and disipate air to/from atmosphere.

I haven't heard of one ever catching fire (that's not to say they couldn't catch on fire) but generallyspeaking they are pretty much low risk.

In this instance if you work on the rule that you only have one fire in a building its unlikely your internal and external staircase would both be compromised, so if the air con units did ever catch fire persons could use the internal stairs to escape.

As one poster has already mentioned where ventilation ducts discharge to atmosphere near external escape routes dampers interlinked into duct mounted sensors or the buildings fire alarm and detection system should be used. Relying purely on intrumescent materials or fusible link dampers is not acceptable as they wouldn't seal the duct quickly enough

In new builds ventilation systems are clearly already designed to discharge well away from external escape routes.