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Minor Gas Leaks in Very large Buildings

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Messy
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Minor Gas Leaks in Very large Buildings

Post by Messy » Thu Nov 28, 2019 7:54 pm

Its all so very easy to draw up an emergency plan for a gas leak effecting a premises. Open windows, isolate gas supplies and evacuate. Simple

But what about very large premises and/or those where closing down business isn't quite as easy as most locations?

Consider the £4.2 billion Terminal 5 at Heathrow. Its 353,020m2 and the main building alone (1/3) takes up the same space as nearly all of the Govt buildings in Whitehall

So would you evacuate the whole of T5 for a minor gas leak at one end? Or is there another recognised risk based system that can be used?

I am assisting drawing up gas leak plans at another very large building - albeit at 100,000m2 is just under a thirds of the space of T5. I have spoken to a number of competent gas engineers including some in the supply and distribution industry who all repeat the same 'ventilate, isolate and evacuate' mantra as if its some kind of religious or prescriptive response rather than a risk assessed approach. Its as if they are more interested in protecting their reputation that giving a professional answer

So has anyone had any dealing with gas leak plans at a very large building that adopts a risk based approach? Or do you know any competent person who I can consult?

Just to confirm, I am talking about minor leaks of natural gas

Photo shows approx size of T5 when overlaid across the Westminster area of London
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Re: Minor Gas Leaks in Very large Buildings

Post by witsd » Fri Nov 29, 2019 9:44 am

I've no experience with this whatsoever, but I have a couple of thoughts:

How are you going to quantify 'minor'? It seems unlikely that you will be able to actually monitor how much is leaking, so unless you have immediate access to some kind of measuring device, you surely have to err on the side of caution?

How can you be sure that you have correctly identified the source? I could be stood next to a gas pipe smelling gas and thinking that it's a minor leak from the pipe in front of me, when it is in fact seeping under the door of the locked plant room behind me, having already built up an explosive atmosphere within.

Sorry to be negative, but I'm not sure how much of this is controllable. :|
We often think that when we have completed our study of one we know all about two, because 'two' is 'one and one.' We forget that we still have to make a study of 'and.'

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Re: Minor Gas Leaks in Very large Buildings

Post by bernicarey » Fri Nov 29, 2019 12:32 pm

Interesting quandary, I can understand Messy's problem but also witsd's stance.

I think the answer lies in what the circumstances are, the layout of the building, where the smell is and so forth.
For example, is the smell anywhere that there is an appliance or a pipeline?
Is it known/confirmed as a natural gas leak or not?

My first port of call in deciding if there was even the potential of having some sort of phased approach to evacuation would be to understand where the gas system was.
There's a big difference between a huge open internal space like a terminal building and an office block.
For starters, Natural Gas has about half the density of Air, so will rise, therefore if you're smelling it at ground level in a large internal open space, there is likely a great deal of it above your head..... :shock:
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