Carbon dioxide doesn't just displace oxygen; it is also toxic in itself. 

You cannot see carbon dioxide in its gaseous form.  What you see in a cloud is droplets of liquid.  The gas that then evaporates off them is invisible.  This is similar to the 'steam' you see from a kettle, which is not gaseeous water but water droplets; water vapour (the gaseous form of water) is likewise invisible.

It is possible to measure carbon dioxide levels (and indeed oxygen levels) in the air and to have an alarm linked to the measurement to trigger evacuation before a dangerous level is reached.

I don't quite understand what is the process that you are doing and how it relates to the carbon dioxide transfer.

Kate, to be honest, I am completely puzzled as the orginal post setting out the question which you answered seems to have been deleted so it's not clear what Paul's question was.

Paul, that said, I think if you have been asked to respond to a question in advance of an interview, the interviewers probably want you to do some homework and not just parrot what people might offer up on a chat forum.

Further, if the interviewers have any competence, then they should be able to easily root out any hint of plagiarism via some secondary questions to let you explain how you have come to your thinking.

Of course, there is nothing wrong with doing some networking and perhaps your original thread showed that you HAD been thinking about the answer for yourself. But, deletion of your initial posting makes it look like something rather different had been put up for others to answer.

Originally Posted by: Westwick27925

It's an interview scenario My details are paul.westwick@dhl.com

Well that attempted quote didn't work.

We do have Private Messaging on the forum so you don;t need to disclose an employer email address.  

The scenario presented in the original post was along the lines of:

My company has been asked to undertake maintenance on a trailer containing a scanner.  The scanner uses liquid CO2 which is piped in from a tank.  The capacity of the tank is a tonne.  We have calculated that if the entire contents of the tank were relased, the air in our working area would be reduced to 10% oxygen which would mean instant asphyxiation.  The owners of the trailer have told us that there has been a leak during filling in the last year.  When the leak happened, there was a large visible gas cloud and the staff immediately evacuated. Our staff are concerned about undertaking this work.

It subsequently emerged that this wasn't true, but an interview scenario.  So no wonder that there was no elaboration on the nature of the maintenance activity.

At room temperature carbon dioxide only forms a liquid at 5 times atmospheric pressure and above. The idea of a container with a tonne of this would worry me. All the applications I have come across use about 1 kg liquid carbon dioxide. The whole system for handling this would have to be engineered to a high standard and  properly maintained.

Originally Posted by: Kate

Carbon dioxide doesn't just displace oxygen; it is also toxic in itself. 

You cannot see carbon dioxide in its gaseous form.  What you see in a cloud is droplets of liquid.  The gas that then evaporates off them is invisible.  This is similar to the 'steam' you see from a kettle, which is not gaseeous water but water droplets; water vapour (the gaseous form of water) is likewise invisible.

It is possible to measure carbon dioxide levels (and indeed oxygen levels) in the air and to have an alarm linked to the measurement to trigger evacuation before a dangerous level is reached.

I don't quite understand what is the process that you are doing and how it relates to the carbon dioxide transfer.

Hi Kate,

Thank you for your clear and informative response.

You're absolutely right—carbon dioxide is not only an asphyxiant but also has toxic effects at high concentrations. In our case, the scanning units involve refilling with CO₂ in either dry ice or liquefied form, which sublimates or evaporates into gas. This process can lead to CO₂ accumulation if not properly controlled, especially in enclosed or poorly ventilated areas.

As part of our COSHH risk assessment, we are now looking into installing fixed CO₂ and oxygen sensors with alarm triggers to ensure that evacuation protocols can be activated well before hazardous levels are reached. Your explanation regarding the invisibility of CO₂ and the misconception around visible vapor was especially useful for reinforcing this need.

Thanks again for your valuable insight.

Good morning Kate

Given that I can't see that your remark would easily relate to anything I have previously written on THIS thread, it's a bit cryptic but I think, from reading other threads, that I understand what you were getting at, and that Roundtuit has as well.

Hi Kate, I wonder whether one user of these Forums could trace their ancestry to link to a man who might have had time to investigate the risks of psittacosis after being severely injured during what the defence argued [in a case in the Court of Appeal in 1965] was a "frolic of his own".

Would AI easily manage to solve that cryptic clue?