hi i was wondering if anyone new how many shots you could get from a fire extinguisher just a 2.0kg one and i will gte my mates dad to fit it with a schrader valve coz i cant weld and i will fill it up with air till it is at its recomended psi thanks to all who post

It depends on the size of the chamber.2kg of CO2 mean about 1000L of gases.You should be able to calculate the rest...

It depends greatly on the kind of extinquisher it is.If it's a CO2 extinquisher you'll be happy Cause those can take 900 psi or 60 bar.
If you fill it with CO2 you'll get a lot of shots out of it.If you use air you'll get a lot less cause air doesn't liquify at that pressure.You can't pile air up into a liquid like you can co2( well you can at 280 bar but that's a different story)
If it's the kind that uses powder ;but is operated by a 16(yes 16)gram CO2 capsule, it's probably only safe up to 18 bar and can't take the liquid CO2.