According to PED 97/23 air is considered as gaz group 2 (non dangerous).
The category is defined with annex 2 table 2. you have to calculate Ps.V (bar.ltr)
For your 2 cylinders you have 2 bar.ltr and 22.4 bar.ltr.
From annex 2 table 2 you can deducted that both cylinders are art3.3 because...
