Posted By Paul Leadbetter
The effects would depend on the resultant oxygen concentration; it doesn't need to drop much below normal (21%) for effects to show.

Paul

Posted By Frank Hallett
This is an extremely contentious area as much of the quoted abilities for people to remain in the affected areas by the fire extinguishing systems providers is directly contradictory to standard CoSHH and H&S approaches for air quality.

Really thorough research is required to determine the acceptable parameters in each individual installation.

Frank Hallett

Posted By Stupendous Man
A short extract from the article I have read:

'OxyReduct continuously reduces the oxygen level in a room by adding nitrogen to the air. The oxygen is reduced to a level in which most combustibles do not inflame and an open fire is impossible. Importantly, people can enter and work in the area of risk at any time.'

I'm interested in the reduction of fire risk that this system appears to offer, but am mindful that it is simply causing new risks to the safety and health of employees.

Posted By Frank Hallett
As I identified earlier - many of these systems are sold on the basis that employees are able to remain within the affected area [this often accompanied by - "with no observable ill-effects"].

As so many allege that their particular formula will not harm the exposed person and yet they are continually promoting a directly contradictory type of atmosphere to that which is considered acceptable under normal H&S approaches; perhaps there is scope for an HSE funded research programme on this topic!!

Without totally independant advice, even those who have an understanding of the issues of respiratory protection and CoSHH are continually met with comments similar to "The Fire experts say that it's OK, why are you disagreeing with them? They wouldn't put it on the market if it wasn't safe".

When presented with this statement, I attempt to ensure that my client has a clear contractual relationship with the extinguishant system provider that brings them within the definition of "competent person" under MHSW and CoSHH. It's amazing how few extinguishant providers will allow themselves to br placed in that position!!

Frank Hallett

Posted By Merv Newman
Also, while an oxygen reduced atmosphere will REDUCE the fire risk it will not eliminate it.

From memory, 18% oxygen, as opposed to the normal 21%, is the lowest to which people can be "safely" exposed although this will vary between people and will be related to atmospheric pressure and thus, eventually, to the partial pressure.

Many materials will quite happily burn at 18% or less.

Everyone knows (even me) that enriched oxygen atmospheres will cause normally "flammable" materials to burn like guy fawkes in a force eight gale.

Lots of people believe that if there is less than the normal oxygen content fires will not happen.

T'aint true.

Again from memory, Freon extinguishing systems put about 5% of the gas into the area. Effectively reducing the oxygen content by about 1.1% and the nitrogen content by about 3.9% This extinguished most fires by interfering with the combustion cycle, and was "safe" for people to breath. (have seen it demonstrated by the salesman) But apparently it also dug big holes in the ozone layer.

CO2 also has it's drawbacks - needs much more in the atmosphere (can't remember how much, 10% ?) and has it's own physiological problems. Needs much more in the atmosphere to work and is not people friendly. Hence need for "double knock and loudshoutsofgetoutgetoutgetout" systems

Which is why people are now flogging nitrogen systems.

Can anyone tell me what level of N2 would be present in these systems ?

Merv

Posted By Robert K Lewis
Have to agree with many of the comments. Whilst theoretically human beings can exist for short periods in atmospheres of around 13-14% oxygen, ie the levels at the lower end of exhaled breath but mouth to mouth does work!, the margin of error is quite small - at 10% unconciousness and death are relatively quick to follow. I would not therefore advocate anyone being actively asked to work in such a reduced oxygen environment. It simply allows the operative opportunity to escape without having to worry too greatly as to timing.

In spite of the environmental concerns the safety case for the halons is stronger than the modern systems. In some premature natal wards the oxygen can be given dissolved in liquid halon with no ill effect and reduced lung damage compared to gas only inhalation - more complex though.

On a final note try and think of how you will justify putting your employees to work in a fire damaged oxygen deficient area to the HSE!!

Bob

Posted By Merv Newman
From reading both reports, it would seem that my opinion is somewhat confirmed. To prevent/stop combustion O2 levels would have to be reduced to less than 10%. Which is what the added-nitrogen systems give. However at this level immediate escape from the area is necessary.

So entering and doing work in such an atmosphere is a no-no.

The three Nitrogen adding systems examined in the HAG report are all extinguishing systems. They are not meant to be used as fire preventing or even to reduce the probability of a fire from starting.

I could perhaps conceive of slightly enriching the nitrogen level in a chamber to lower the combustion rate but I think it would be a waste of breath.