I intend on using the Mini O2 Portable to test O2 directly from a cylinder pressurised to 2500 PSI, is this pressure OK for this unit? 


You have 2 options when testing your air with the O2 Portable device:


1. Regulate your pressure down to approximately 2 BarA and pipe it to the device at 2 litres per minute


2. Open the cylinder until you hear the gas gently hissing out, then -with the DII dome adapter fitted- apply the device firmly against the cylinder.