Gas riser in a block of flats

[Bill G]

Ladies & Gents

Can you please help - I have a block of flats built about 1960 . It has 17 floors with one staircase. On each level are 6 flats that all use a communal lobby. Within the lobby are two service risers, one for gas and one for the electrics etc. both are enclosed with FR as required and are sealed at floor/ceiling on each level. The gas supply to the building is via a riser situated in the staircase enclosure ( which has an open lattice side to fresh air). The riser pipe then branches at each level and goes into the gas cupboard at each level in the lobbies ( from there the pipewok splits into the individual laterials for the flats).

The problem is that our FRA company have noted that within the staircase enclose there are ventilation bricks which serve the gas cupboards at each level. They have advised as the staircase is the only one for the building than these vents should be sealed. Our utility supplier has requested that if we close up the ventilation bricks into the staircase then we should provide top and bottom venting for the entire shaft. We are not over keen on breaching the floor level compatmentation to provide a shaft. This situation has been in place for over 50 years now and we are seeking a safe way forward ( money is not a problem ) . Would you keep the existing staircase ventilation?. Would you provide ventilation into the lobby with gas detection?. Would you create the top and bottom shaft? , what are your thoughts. 

[nearlythere]

Ladies & Gents

Can you please help - I have a block of flats built about 1960 . It has 17 floors with one staircase. On each level are 6 flats that all use a communal lobby. Within the lobby are two service risers, one for gas and one for the electrics etc. both are enclosed with FR as required and are sealed at floor/ceiling on each level. The gas supply to the building is via a riser situated in the staircase enclosure ( which has an open lattice side to fresh air). The riser pipe then branches at each level and goes into the gas cupboard at each level in the lobbies ( from there the pipewok splits into the individual laterials for the flats).

The problem is that our FRA company have noted that within the staircase enclose there are ventilation bricks which serve the gas cupboards at each level. They have advised as the staircase is the only one for the building than these vents should be sealed. Our utility supplier has requested that if we close up the ventilation bricks into the staircase then we should provide top and bottom venting for the entire shaft. We are not over keen on breaching the floor level compatmentation to provide a shaft. This situation has been in place for over 50 years now and we are seeking a safe way forward ( money is not a problem ) . Would you keep the existing staircase ventilation?. Would you provide ventilation into the lobby with gas detection?. Would you create the top and bottom shaft? , what are your thoughts. 

Bill. What is the FRA's reason for sealing up the vents?

[Bill G]

There concern was the leakage of gas into the staircase enclosure. 

[nearlythere]

There concern was the leakage of gas into the staircase enclosure. 

That would not be my concern Bill. What would be the chance of a leak occurring? This is static equipment with no moving parts other than an isolation valve and a leak would be extremely unlikely unless the equipment was tampered with.
Has the FRA company found that such installations are prone to developing a leak in the service shafts?

[Bill G]

In one sence the chances of a leak are remote and would I rather a leak go into a vented starcase or inot an enclosed lobby> although neither is perfect the leakage into the staircase is the best of a bad job, apart from ripping the while lot out and starting again .  What is a factor is that the joint work in the cupboard is compression joints . Which from a laymans point of view does not seem right to me ( what was more alarming was the comment form the utility company - in that he did not know waht a compression joint looked like !!!).

The FRA company - Im not sure , I suspect that it started out as a general comment and when questioned they have stuck to their guns and have taken a hard line to cover themselves ( which I dont have an issue with )

[nearlythere]

In one sence the chances of a leak are remote and would I rather a leak go into a vented starcase or inot an enclosed lobby> although neither is perfect the leakage into the staircase is the best of a bad job, apart from ripping the while lot out and starting again .  What is a factor is that the joint work in the cupboard is compression joints . Which from a laymans point of view does not seem right to me ( what was more alarming was the comment form the utility company - in that he did not know waht a compression joint looked like !!!).

The FRA company - Im not sure , I suspect that it started out as a general comment and when questioned they have stuck to their guns and have taken a hard line to cover themselves ( which I dont have an issue with )

I think the utility company might have little to do with the installation. Compression joints would not be an issue as valves and regulators on a gas pipe would be easier and safer to remove using a spanner rather than heat. In any event the installation and equipment has to be installed to the appropriate standard.

[wee brian]

There's nothing to stop you running a gas main up the protected stairway.

Leave the vents where they are as they reduce the risk of a build up of gas, if there is a leak.

[Tom Sutton]

Is there high and low level ventilation in each cupboard via the staircase enclosure?

[Bill G]

Yes - at the moment each of the cupboards are vented through the shaft wall into the staircase by means of two 6x4 air bricks .

[nearlythere]

Yes - at the moment each of the cupboards are vented through the shaft wall into the staircase by means of two 6x4 air bricks .

You might have to have a look at the older guide on Flats and Maisonettes to check if it complied then.

Remember that the Fire Risk Assessment does not belong to the Assessor who assisted you - it belongs to your organisation. If you don't agree with their assessment on certain issues you can amend to make it more suitable and sufficient.

[Tom Sutton]

Because the inlet and exhaust vents are located in the staircase, if there is a leak in the gas cupboard then gas will enter the staircase. Because natural gas is lighter than air it will rise to the head of the staircase and if there is permanent ventilation at the head, could gas build up to an explosive concentration, 5 to 15 percent I understand?

[Bill G]

Tom -

The staircase is enclosed on three sides with a brick lattice wall to freshair at all levels.

regarding the risk assesment - yes we apprecitae that the FRA is ours to own . But before we make any final decision on what to do we are seeking the best and safest solution as the last thing we want to do is make any mistake regarding gas supplies in a tower block.

[nearlythere]

Tom -

The staircase is enclosed on three sides with a brick lattice wall to freshair at all levels.

regarding the risk assesment - yes we apprecitae that the FRA is ours to own . But before we make any final decision on what to do we are seeking the best and safest solution as the last thing we want to do is make any mistake regarding gas supplies in a tower block.

Bill G. The best and safest solution is to remove the gas completely. That is probably not practical so therefore what you want to do is to identify any risk, analyse it and then consider if the measures in place control that risk to a reasonable level and if any further measures are necessary.
Your advisers have presumably identified the risk, analysed it and considered that the existing measures are not suitable and sufficient, or, they may have found a gas supply, thought shoot, that's gas! so it must be dangerous and reasoned that they, first and foremost, should at least cover their asses.   

[Bill G]

to those who have replied - thank you.

I am inclined to leave the situation as it is. It is not practical to create a top to bottom shaft within the gas cupbards on each level as this would intail breaching the comparmentation at each level. I am not inclined to vent into the lobby to the flats as this is an enclosed space with ignition sources. The best is to allow the supply to vent into the staircase ( this is vented to fresh air at each level) .  The only danger then is the detection time from start of a leak to it's detection and the time taken to close off the supply. Therefore it may be possible to insert a gas detection system in the staircase linked to a solinoid to switch of the gas supply at the intake point.

[kurnal]

Hi Bill

If in England/Wales I assume you have taken into account of ADB para 2.42 on page 31 and para 8.40 on page 79 ? These paras set out what would be permissible in a new build.