Posts Tagged ‘radiation dose’

Hazards of Flying

November 17, 2019

Radiation Dose

Radeye in Cabin

RadEye Geiger Counter on my lap in the plane.

It is well-known that by flying in commercial airliners, one exposes oneself to increased intensity of ionising radiation.

But it is one thing to know something in the abstract, and another to watch it in front of you.

Thus on a recent flight from Zurich I was fascinated to use a Radeye B20-ER survey meter to watch the intensity of radiation rise with altitude as I flew home.

Slide1

Graph showing the dose rate in microsieverts per hour as a function of time before and after take off. The dose rate at cruising altitude was around 25 times on the ground.

Slide2

During the flight from Zurich, the accumulated radiation dose was almost equal to my entire daily dose in the UK.

The absolute doses are not very great (Some typical doses). The dose on flight from Zurich (about 2.2 microsieverts) was roughly equivalent to the dose from a dental X-ray, or one whole day’s dose in the UK.

But for people who fly regularly the effects mount up.

Given how skittish people are about exposing themselves to any hazard I am surprised that more is not made of this – it is certainly one more reason to travel by train!

CO2 Exposure

Although I knew that by flying I was exposing myself to higher levels of radiation – I was not aware of how high the levels of carbon dioxide can become in the cabin.

I have been using a portable detector for several months. I was sceptical that it really worked well, and needed to re-assure myself that it reads correctly. I am now more or less convinced and the insights it has given have been very helpful.

In fresh air the meter reads around 400 parts per million (ppm) – but in the house, levels can exceed this by a factor of two – especially if I have been cooking using gas.

One colleague plotted levels of CO2 in the office as a function of the number of people using the office. We were then able to make a simple airflow model based on standard breathing rates and the specified number of air changes per hour.

Slide5

However I was surprised at just how high the levels became in the cabin of an airliner.

The picture below shows CO2 levels in the bridge leading to the plane in Zurich Airport. Levels around 1500 ppm are indicative very poor air quality.

Slide3

Carbon dioxide concentration on the bridge leading to the plane – notice the rapid rise.

The picture below shows that things were even worse in the aeroplane cabin as we taxied on the tarmac.

Slide4

Carbon dioxide concentration measured in the cabin while we taxied on the ground in Zurich.

Once airborne, levels quickly fell to around 1000 ppm – still a high level – but much more comfortable.

I have often felt preternaturally sleepy on aircraft and now I think I know why – the spike in carbon dioxide concentrations at this level can easily induce drowsiness.

One more reason not to fly!

 

 

 

xkcd

March 21, 2011
xkcd illustration of radiation dose

xkcd illustration of radiation dose. Click for larger version

Last week I struggled to express as clearly as I could the key quantities relating to measurements of radiation dose. I felt it would help to make sense of some of the very few numbers emerging from Japan with respect to the Fukushima nuclear crisis. But things can always be said another way, and my friend drew my attention to an interesting graphical representation of dose – see the figure at the head of the article – devised by the Randall Munroe at xkcd. I love it. I love the way this graphical representation engages one’s mind in quite a different way to the effect of numbers and text. Incidentally, the article is released under a licence which means that if you are not trying to make money out of it, you are welcome to share it. I appreciate that.

xkcd is a slightly odd site demonstrating a ‘physicsy’ kind of humour, to which end I thought you might enjoy the following gems. They are self-explanatory – and some of them are literally self-explanatory! – so I leave them with you for what they are worth. Goodnight.

 

Representation of the scale of the universe as 'height'

Representation of the scale of the universe as 'height' -Click for larger version

A self-explanatory cartoon

A self-explanatory cartoon

Haven't you ever felt this way?

Haven't you ever felt this way?


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