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Posted By Al..
Has anyone had experience of fire protection systems which are supposed to create an environment in which fires cannot start by reducing oxygen levels via the continuous addition of nitrogen to the air? Claims are made that people can enter and work in these areas at any time. I hear that they have been used in libraries (or at least in their archives). Confined space entry permit anyone?
Al
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Posted By Ashley Wood
These systems are very good but there is a time limit on continuous exposure, I believe it is 6 hours. However, I have spoken to people who have been in an N2 rich atmosphere and after an hour they started to feel a little lite headed. I think that there is a case for confined entry type classification to be considered.
One of the draw backs with this system is the loss of the N2 generator when the system is being maintained. To guarantee continued protection you must specify a back up unit that would take over when the primary unit is down.
I believe there are several libraries being protected with this type of system, the latest being in Oxford for the British Library. Only one manufacture exists so I don't suppose the moderators will mind me mentioning them! WAGNER located in Cambridge. If more info needed contact direct.
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Posted By Konstanty Budkiewicz
Al..
I have no formal experience of breathing Nitrogen. I searched the Web under "effects of breathing nitrogen" and found a number of sites: they were mostly concerned with diving. However, the following link is the equivalent of an MSDS and should be of use to you. It features the PERMIT TO WORK scenario that you querried: http://intox.org/databan...mical/nitrogen/cie56.htm
Kon CMIOSH
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Posted By steven n
Nitrogen is regularly used to purge tanks/vessels and it has always been my understanding that it is a case of two breaths and you're dead. It is commonly used in electrical switch rooms to extinguish fires where there is easy exit and a control on entry.
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Posted By Jane Blunt
I believe that these systems are designed to take the oxygen concentration below 15%, to extinguish the fire. However, I believe that they are also designed to keep the oxygen level above 12.5%, which will not harm people in a very short exposure.
Hence the fire is extinguished but not the people!
Jane
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Posted By Ashley Wood
yes, its all about oxygen reduction and not elimination! I believe they do something similar in aircraft hence the reason why you feel sleepy on long hall flights, Myth or fact I do not know for sure. Anyone out there know?
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Posted By Al..
Thanks to all for the information. I see that a supplier recommends that people can work in the areas protected by low oxygen levels down to 13 percent providing that they have undergone a health check.
Some quoted symptoms of oxygen depletion are
21 to 14 percent
Increasing pulse rate, tiredness
14 to 11 percent
Physical movement and intellectual performance becomes difficult
11 to 8 percent
Possibility of headaches, dizziness and fainting after a fairly short period of time
8 to 6 percent
Fainting within a few minutes, resuscitation possible if carried out immediately
6 to 0 percent
Fainting almost immediate, death or severe brain damage
I guess that you will want to know that there are robust arrangements in place to prevent the oxygen content going below 13 percent. Will those robust arrangements there will not then be a foreseeable risk of an unbreathable atmosphere and no confined space. Looks a smart idea. Why has no one thought of it before?
Al
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Posted By Kenneth Patrick
Because you need robust arrangements it will be a Confined Space. This is a general principle.
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