Curious now as to the reasons behind switching to manual when the area is occupied.Bearing in mind the nature of the agents now used health risks are minimal to anyone caught in a discharge (indeed,if serious medical conditions arise then it's more likely due to a wrongly designed system and that too much extinguishant was released).

Heres the science part -

Normal atmosphere in a room is 21% O and 1% CO2 and anything above 15% O is enough for combustion to occur.

In the case of Inergen the extinguishant drops the O level down to 12.5% but increases the CO2 level to 4% - more CO2,surely not??Well,the CO2 stimulates the body to breathe more deeply and rapidly to compensate for the lower level of O.

FM200 and FE227 show little depreciation of O %.

CO2 is nasty and procedures are a must with it (was caught in a van when a valve went off and it wasn't pleasant).

The main reason for switching to manual (as I see it) would be where work was being carried out that may lead to accidental discharge (hot work,air-com maintenance etc.). This work should be under special work permits anyway and within these there would be procedures in plae to facilitate auto/manual/auto switching.

Occupancy sensors in all covered rooms on a 10 minute on delay, no keys to worry about but they would have to ignore smoke and flame, not so easy!

Occupancy sensors in all covered rooms on a 10 minute on delay, no keys to worry about but they would have to ignore smoke and flame, not so easy!

Yeah until the operator sits at his desk for an hour typing away and the delay runs out and it switches to auto... then sods law it goes off...... this will put it into 1st stage... if the operator moves presumably the system will revert to manual. So a second detector activating will not put the system into 2nd stage and therefore there wil be no automatic discharge....?

So now you are getting in to the realms of people remembering to hit a manual release....??

Sounds all too over complicated to me..... and far too much trust in a PIR and technology..... look what happened in Terminator.......!!

We've used the chubb key system a few times, never had a problem.

Yeah until the operator sits at his desk for an hour typing away and the delay runs out and it switches to auto... then sods law it goes off...... this will put it into 1st stage... if the operator moves presumably the system will revert to manual. So a second detector activating will not put the system into 2nd stage and therefore there wil be no automatic discharge....?

So now you are getting in to the realms of people remembering to hit a manual release....??

Sounds all too over complicated to me..... and far too much trust in a PIR and technology..... look what happened in Terminator.......!!

We've used the chubb key system a few times, never had a problem.

Agreed!

The CHUBB lock/microswitch is the better solution over a status change over unit where someone has to unlock then lock a door,controlling entry and the auto/manual status - agreed.

However,I was just curious as to why this is still necessary - is it just that it's a case of "oh,err - there's gas in there so keep staf away from it" or is it due to concerns over hearing damage due to the noise of the extinguishant being releasede?

As i said in my first post.... probably no reason why it can't be left in auto all day long.... tis just urban myth and chinese whispers regarding the gas.........

As i said in my first post.... probably no reason why it can't be left in auto all day long.... tis just urban myth and chinese whispers regarding the gas.........

Sorry Dave - that long ao I'd forgot that you'd said that!!

You probably get more injuries with the ceiling coming down , than a sharp intake of agent.

We always tried to get the client to fit a Chubb mortise lock with built in microswitch connected to the manual/auto switch.

When the door was unlocked system went to manual, lock the door, system goes to auto.

I 'suppose' you could use an occupancy PIR to do the same thing?

What happens if your working in the area, shift changes, security guard or somene else intelligent notices the doors unlocked, goes 'tut tut tut' and locks it !

Personally, I like to see the key turned and see the indicator lights change for myself, that stuff scares the life out of me since somene explained what halon can do ! and even though I dont think you see Halon anymore it still scares me.

What happens if your working in the area, shift changes, security guard or somene else intelligent notices the doors unlocked, goes 'tut tut tut' and locks it !

Personally, I like to see the key turned and see the indicator lights change for myself, that stuff scares the life out of me since somene explained what halon can do ! and even though I dont think you see Halon anymore it still scares me.

(a) Halon not (or shouldn't be around)

(B) Unless it's CO2 then see above post (8 or 9 back) for basic guide to why it's safe!

Bear in mind as it's an electrical activation then it can discharge through equipment malfunction or some bright spark hitting the manual release.