Monday, 1 April 2013

Drowning in CO2

A few years ago I was sat in a rather dull meeting at The Spa in Scarborough. The meeting room was lit by chandeliers each containing about 20 incandescent light bulbs. As my mind wandered I began to estimate how much CO2 was being emitted to produce the electricity used during the meeting and then imagined what would happen if this CO2 was pumped into the room.

What follows is a recreation of the original calculation.

There were 6 chandeliers each with 20 bulbs. Assuming each was rated at 60W this gives a total power consumption of 7200W (6 x 20 x 60W) = 7.2kW

The meeting lasted about 2 hours so the total energy used was 14.4kWh (7.2kW x 2h)

For each kWh of electricity the average quantity of CO2 emitted is 0.47kg

So the total CO2 emitted was 6.77kg (14.4kWh x 0.47kg/kWh)

At standard temp. and pressure the density of CO2 is about 1.98kg/m3

So, the volume of CO2 emitted was about 3.4 m3 (6.77/1.98)

The room was about 6m x 5m and therefore had an area of about 30m2

CO2 is denser than air so, if the air in the room was still, could form a layer along the floor about  0.11m = 11cm deep (3.4m3/30m2).

Estimating a typical sitting nostril height of about 1.10m this means you'd have to sit through 10 meetings, one after the other, before anyone was at serious risk of drowning in CO2 

Now, either there were more bulbs, the room was smaller or I underestimated the density of CO2 , but I remember that I thought we were just about to have to stand up to avoid choking on our own emissions. 

It seems the meeting would have had to have been even longer to put us out of our misery.

Postscipt: I must learn some way of putting in subscripts and superscripts without having to go into HTML

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