Detection in Heritage Building

[Gasmeter]

In a mid 19th century Grade A listed building, a large hall of brick and timber construction and a pitched roof with ornate timber trussing has point detection at roof ridge level, 15.7m high.  To improve the AFD, I considered an aspirating system, but am informed that a fairly complex beam system is required.  Just to complicate matters, access to roof level is difficult, making installation and future maintenance an expensive nightmare.  Does anyone out there have an inspired suggestion for an alternative approach?

[Allen Higginson]

In a mid 19th century Grade A listed building, a large hall of brick and timber construction and a pitched roof with ornate timber trussing has point detection at roof ridge level, 15.7m high.  To improve the AFD, I considered an aspirating system, but am informed that a fairly complex beam system is required.  Just to complicate matters, access to roof level is difficult, making installation and future maintenance an expensive nightmare.  Does anyone out there have an inspired suggestion for an alternative approach?

Can I ask the reasoning behind the requirement of a beam system over an aspirating system?
I know which one I reckon will go off first in the event of a fire and surely this is paramount in a heritage building?

[John Webb]

I am likewise of Buzzard's opinion. How do they check the existing point detectors at that height?!

[kurnal]

Whats the Hall used for and what is the nature of the contents?

[Allen Higginson]

I managed to miss the height (should have went to Specsavers). The maximum height for point detection (smokes) in a P category system (with rapid attendance) is 15 metres,so they are currently outside of that.
An aspirating system (on a P system with rapid response) can be at either 17 metres (enhanced) or 20 metres (high sensitivity).However,the normal setting aspirating system has a maximum height the same as point detection (as each sampling port is a "detector") - this may be why the aspirating system has been rejected.
Beams can be up to 40 metres on a P system with rapid response.

[John Webb]

If the timber trusses are ornate (which implies some depth to them) and with king posts etc., there could be problems getting a beam system reasonably close to the apex of the ceiling - an aspirating system may be preferable therefore. And have any checks been carried out for stratification during the heating season which could significantly delay the smoke getting to either point, aspirating or beam systems?

[Gasmeter]

Thanks to all for your replies; the hall is wood paneled to about 4m with numerous large portraits on the walls above, it hosts dinners, conferences etc. and the trussing is queen post type.  The only option for maintenance is scaffolding as there's no access for a scissor lift or similar, the suggested beam system would involve a grid at an intermediate height with a further beam at ridge level.  No modeling has been done as the consensus is that quite apart from the maintenance problems there would indeed be stratification, which is why I'm looking at the available options.  I expect there'll have to be a compromise.

[kurnal]

Is the proposed detection for life safety or property protection? The Hall itself sounds low risk in terms of life safety.
What ignition sources are present ? I am thinking if for property protection and especially if  there are specific ignition sources in a room of predominantly low risk video smoke detection may be a decent solution.

[John Webb]

....The only option for maintenance is scaffolding as there's no access for a scissor lift or similar.....

What about the 'Beanpole' type hydraulic lift - goes through a standard doorway but can reach around that height? But I don't know if they are still made as it's some 15+ years since I last used one.

[Gasmeter]

This would be for property protection, event management is very good.  Ignition sources would be very limited, perhaps table candles occasionally and sound systems but again these things are well managed. I'm not familiar with the 'beanpole' type of lift, it may help, part of the problem is that one of the existing detectors is directly above a raised stage area at one end of the hall with no access for any kind of lift, unless there's an anti-gravity one available  

[Thomas Brookes]

Speedy Hire do a single man lift that goes through a normal door, we used one recently in a small dance studio. We had to set it up on ply boarding to spread the weight.