# Question 18.1

a) What gas is delivered through this cylinder shown in the photograph?

b)  When  this  gas  is  delivered  in  the  ICU  through the  wall  outlet,  what  is  the pressure at the wall outlet?

c) What is the pressure of the gas in a full cylinder?

a) What gas is delivered through this cylinder shown in the photograph?
Oxygen

b)  When  this  gas  is  delivered  in  the  ICU  through the  wall  outlet,  what  is  the pressure at the wall outlet?
The Australian Standards are 415 kPa static pressure in pipeline, which is allowed to fall to by a maximum of 50 kPa under some conditions. Therefor any answer between 365 and 415 kPa was acceptable.

c) What is the pressure of the gas in a full cylinder?
Whilst it varies from cylinder to cylinder, any answer between 12 to 17 megapascals (12000-17000kPa) , is acceptable.

## Discussion

Yes, even though that says "N", it is in fact an oxygen cylinder, ready to be transported to a CT scan. And the porter was taking so long that I started taking pictures of the scenery.

The standard (mandatory) wall gas pressure is indeed 415 kPa (about 4 atmospheres). For the gas which powers surgical tools, the pressure is 1400 kPa.

The cylinders, according to a reputable source, can withstand a pressure of 24,000 kPa, but normally rest at around 12,000-17,000 (that is the "green zone" on the gauge).

## References

This excellent lecture from the University of Sydney has a vast amount of obscure information (did you know oxygen tanks are aged at 175°C for 8 hours, and that their walls are only 3mm thick?)

Medical Gas Standard AS 2896-2011 is available online, but you have to pay over \$200 to purchase it.

Dorsch and Dorsch have a chapter dedicated to medical gas supply and suction equipment, which can be accessed by Google Books.