I am trying to estimate the amount of energy stored in a firefighting breathing air cylinder, so I can give my students a grasp and respect of the danger of mishandling their cylinders.

I have looked around for some basics, and found a few threads referncing NIST data

Post 5 on physics forum, but I can't seem to find the source.

695D Cylinder on second page is what we use.

It is a 6.75 liter cylinder pressurized to 310 bar (4500 psi) to provide around 45 minutes working time.

In the physics forum thread, they reference a 490cc cylinder at 200 bar having 19,237 J energy using NIST data.

If I scale that linearly and divide the 6750cc volume of the cylinder I use versus the 490cc example I get 13.776 times as much volume and 310bar/200bar 1.55 times as much pressure.

(6750cc/490cc)(310bar/200bar)(19237J)=410,749 J

Does this seem right?

Continuing on

NIST TNT Energy Equivalent is 4184J/g
(410,749J)/(4184J/g)=98.17g

So somewhere around the same energy as 98g of TNT?

Am I doing it right?

Edit: I realize that this may be ignoring whether or not it is an adiabatic release....